[appengine-java] Re: Converting Entity to Object

[vbart]

1. you can also try AuDAO, which allows you to generate DAO layer over
GAE low-level datastore API. The DAO layer also includes the methods
for converting between DTO (e.g. Contact, User) and GAE Entity
objects, so you do not need to write them manually - they can be
generated. The way of conversion is the fastest one - no reflection is
used.
http://audao.spoledge.com

2. I think that the low-level API Query class is not so powerful as
the JDO's one - no "!=", "IN" nor ".contains()"... operands and
methods are supported. But it is probably faster - as it is the low-
level API which also the JDO framework probably uses.

Also in JDO you can dynamically construct queries using JDOQL. In low-
level API you must explicitly call method query.setFilter() for each
property.
So as a part of AuDAO we developed a free GQL parser (you can download
sources from the audao site). Using it, you can also create dynamic
low-level queries:
Query lowLevelQuery  = new GqlDynamic().parseQuery( "SELECT * FROM
Contact WHERE firstName=:1 AND lastName=:2", "Jack", "Black");

Vaclav

On Feb 2, 12:08 pm, Alexandru Farcas  wrote:
> Is there a way of converting dynamically an Entity to a specific
> Object ?
> For example:
> I have some Contact objects and User, Invoice etc, witch are
> PersistanceCapable.
> So i can make queries (javax.jdo.Query) that return lists of those
> kind of objects (Contact, User, Invoice etc) or i can use app engine
> datastore.Query to get lists of Entity objects.
> 1. Is there a simple method of converting an Entity object to a
> Contact for example? but without doing smth like :
>         map = entitiy.getProperties();
>         Contact c = new Contact();
>         c.setProperty1(map.get("property1"));
>         c.setProperty2()
>         ... etc
>
>       I want to know this because i want to use Query from the
> datastore package and not javax.jdo and it doesn't seem a good
> solution to make a method for each kind of entity. (I could use java
> reflection to create the objects, but i think it is very complicated
> since i don't know for example the types of fields and it is probably
> a costly method).
>
> 2. Is the Query class form app engine datastore package more powerful
> (or more suited) than the one from javax.jdo? Witch would you
> recommend ?

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[appengine-java] Re: Incorrect number of entities returned

[aswath satrasala]

Hello
Anything wrong here.
I have two classes Tenant and SecurityGroup.
* Create Tenant
* Create SecurityGroup
* Add SecurityGroup to Tenant
* Persist.

* Create another SecurityGroup entity.
* Persist

When I query the datastore for SecurityGroup entities, I get back one entity
instead of two.

Any ideas?

Following is the code for the two classes.
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Tenant {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName = "datanucleus", key="gae.encoded-pk",
value="true")
private String id;

@Persistent
@Extension(vendorName = "datanucleus", key="gae.pk-name", value="true")
private String name;

@Persistent
private List secGrpList = new ArrayList();
}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class SecurityGroup {

@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName = "datanucleus", key = "gae.encoded-pk", value =
"true")
private String id;

@Persistent
@Extension(vendorName = "datanucleus", key = "gae.pk-name", value =
"true")
private String name;
}

Thanks


On Thu, Jan 28, 2010 at 5:14 PM, aswath satrasala <
aswath.satras...@gmail.com> wrote:

> I have the following unittest code.  I am persisting two SecurityGroup
> entities, one as a child of Tenant and one entity not having any parent.
>
> beginTxn();
> Tenant tenant = new Tenant();
> SecurityGroup securityGroup = new SecurityGroup();
> securityGroup.setName("PARTYMGRADMIN");
> tenant.getSecGrpList().add(securityGroup);
> pm.makePersistent(tenant);
> commitTxn();
>
> beginTxn();
> securityGroup = new SecurityGroup();
> securityGroup.setName("PARTYMGRADMIN1");
> pm.makePersistent(securityGroup);
> commitTxn();
>
> beginTxn();
> Query q = pm.newQuery(SecurityGroup.class);
> List results = (List) q.execute();
> assertEquals(2, results.size());
> commitTxn();
>
> I get results.size() as one. I am expecting the results.size() as two
>
> -Aswath
>

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[appengine-java] Re: is google app engine a real-time cloud?

[mete]

Hello Enrique,

You have said that it is possible to hit 2 different datacenters. I
believe appengine has a single primary dc and other one is just a
passive failover. Am I wrong on this ? Does appengine have multiple
active dcs ?

Thanks.

Mete

On Feb 3, 5:47 am, Enrique Perez  wrote:
> Ok, so I will take a shot at this one
>
> Alot of the non-SQL datastores emerging are implementing consistency
> models known as "Eventually Consistent".  SimpleDb at Amazon is one of
> these.  The idea is that when your thread of execution writes to the
> datastore your write call returns back from the datastore write call
> fairly quickly and if you tried to read back your newly written entity
> you may or may not get it back.  But, eventually you would, maybe some
> number of seconds later. There are many systems we use this
> consistency model today.  Email, for example
>
> Per Ryan Barrett, in Google I/O 2008 - Under the hood of datastore, he
> described App Engine datastore as "Strongly Consistent".  Other well
> known "Strongly Consistent" systems you might have used are relational
> databases or file systems.  When you write an entity to the App Engine
> datastore, the call blocks and only returns after the entity is
> written to the entity table, and all indexes rows are written or
> updated.  Within the same thread of execution, if you were to try to
> read back your entity you would always get it back.
>
> Now, there is another factor at play here which I have observed with
> apps running in production. If you running your primary browser doing
> datastore writes, you can open a second browser on different machine
> and bring up your dataviewer. After you perform a write on browser #1,
> you can refresh your second browser which is pointing to the data
> viewer.  Quite often you will not see the results of write from
> browser #1 until some seconds later.  I assumed that this was related
> to the fact that the second browser was hitting a different data
> center, or datastore clustor, and the replication from datastore
> clustor #1 to datastore clustor #2 had not yet occurred.  In Google I/
> O - 2009 - Weekend Projects - Barrett describes App Engine Multi-
> homing techniqes.  App Engine datastore is using Master-Slave
> replication system which is I believe explaining why my browser #2
> takes some seconds to see the change.
>
> However, even with this behavior related to Multi-homing Master-Slave
> replication in place, the App Engine datastore is still described as
> "Strongly Consistent".  If one were to implement Multi-Homing Master-
> Slave replication with relational database technology I believe one
> would still see the type of behavior I have just described.
>
> Hopefully this make sense and I have explained this correctly.  If I
> have gotten something wrong I would love to get a better understanding
> of this.  I love to hear any more detailed information on how things
> work under the hood from those that know ...
>
> Thanks
> Enrique Perez
> Austin, Texas
>
> On Feb 2, 8:09 pm, smile laugh  wrote:> hello everyone
>
> > someone said that cloud computing is not real-time platform.
>
> > that is to say, if you insert a record into cloud(such as bigtable),
> > and then if you query the record immediately , maybe no rowset
> > returned.
> > because in a cloud platform, a record is store in lots of server , at
> > that time when you query that inserted record , some server may not be
> > synchronized , and your query is done in those server
>
> > is that true?
>
> > thanks in advance

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[appengine-java] Re: Persisting during scheduled maintenance periods using JDO

[Andrei]

I have suggestion for GAE
Since it's possible to have multiple versions, why not have a version
u set from admin
console, which will be switched to automatically during down time

On Feb 2, 5:23 am, Ian Marshall  wrote:
> In the GAE/J documentation under "How-To | Handling Scheduled
> Maintenance Periods", it states:
>
> "During this period, all datastore writes and transactions will throw
> an exception. Your application can detect these errors and indicate to
> the user that the application is in read-only, recommending that they
> try again later."
>
> An example is then given to catch the relevant exception during
> PersistenceManager#makePersistent(...), but I cannot find an example
> for datastore updates of already-existing entities.
>
> Does anyone know at what point an update to a persistent entity (not
> using PersistenceManager#makePersistent(...)) will result in the
> CapabilityDisabledException exception being thrown? For example, where
> in the following code extract could I expect this exception?
>
>     // Non-GAE method to return the singleton instance
>     PersistenceManagerFactory pmf =
> DataExchange.getPersistenceManagerFactory();
>
>     PersistenceManager pm = pmf.getPersistenceManager();
>     Transaction tx = pm.currentTransaction();
>
>     try
>     {
>       tx.begin();
>
>         // Non GAE method to get a detatched instance by its ID
> (within the current tx)
>         Item itemEdit = findItemByID(tx, pidData.loID,
> loLoggedOnUserID);
>
>         // Non GAE method to amend the itemEdit instance
>         itemEdit = updateItemWithPageItemData(tx, itemEdit, pidData,
> ipmMode);
>
>         tx.commit();
>     }
>     finally
>     {
>       try
>       {
>         if (tx.isActive())    // Because of an exception, say
>         {
>           tx.rollback();
>         }
>       }
>       finally
>       {
>         pm.close();
>       }
>     }

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Re: [appengine-java] Re: non-deterministic datastore behaviour while unit testing

[John Patterson]

On 3 Feb 2010, at 04:22, Markus Scheidgen wrote:


But you change it a little bit,
maybe comment some unimportant line, and it stops working.


hmmm that sounds suspiciously like a build problem.  Are you sure the  
project is always building?  i.e. no "missing dependancy" errors in  
the Eclipse (or whatever) problems panel.  Or could your debugging  
session be inconsistent?


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[appengine-java] Re: Object state from a query

[Brandon]

According to the spec, the query results may appear in hollow,
persistent-nontransactional, or persistent-clean, at the choice of the
implementation. What state does datanucleus choose?


On Feb 3, 1:01 pm, datanucleus  wrote:
> Obviously the state has a general rule; the JDO spec.
> Just that you can use JDOHelper.getObjectState to tell you what is the
> rule, since it follows the spec

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[appengine-java] Re: is google app engine a real-time cloud?

[smile laugh]

Enrique Perez

thank you so so much

laughsmile

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[appengine-java] Re: GAE For Java with struts2 And I am not able to access development admin console

[MKumar]

Thanks Andy Booth,

You had answered very well to my problem, Now I got the nudge of the
problem. I will opt my self for this scenario.

Mrityunjay Kumar

On Feb 1, 6:05 pm, "andy.booth"  wrote:
> This occurs with most frameworks that use a filter with a wildcard
> mapping to dispatch all requests, the Development server's admin
> Servlets are no longer found, and are instead being processed by the
> your framework (Struts).
>
> 
>         frameworkDispatcher
>         /*
> 
>
> I'm unsure on the best way to resolve this - as I'm not from a Java
> background, I don't know the best way to set up the filter mappings.
>
> However, when I required access to the Admin in Development, I simply
> temporarily commented out the framework's default filter with the
> wildcard mapping, accessed the Admin, then added the filter again when
> needing to run the app.
>
> Andy
>
> On Jan 30, 1:11 pm, MKumar  wrote:
>
> > Hi,
> > I am using JAVA GAE , Everything is working fine, but I am not able to
> > access the Admin console, which as given in documentation can be
> > accessed usinghttp://localhost:/_ah/admin
>
> > But its giving me following error:
> > HTTP ERROR: 404
>
> > There is no Action mapped for namespace /_ah and action name admin.
> > RequestURI=/_ah/admin
>
> > For your information, I had neither used data storage, or queing etc.
> > in application, But wanted to directly enter some data using admin
> > console.
>
> > Please give me some idea so I can access the admin console for data
> > entery on development server.
>
> > Thanks
> > Mrityunjay Kumar

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[appengine-java] Re: Object state from a query

[datanucleus]

Obviously the state has a general rule; the JDO spec.
Just that you can use JDOHelper.getObjectState to tell you what is the
rule, since it follows the spec

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[appengine-java] Seeing owned/child entities in the datastore viewer

[Daniel Benamy]

Hi,

I'm trying to find a way to see the relationships between entities in
the data store viewer. If I have:
class A {
B foo;
}
and I'm looking at an instance of A in the data store viewer, is there
any way for me to find its B? I feel like this should be pretty simple
and maybe I'm just missing something dumb but I've searched a bunch
and can't figure this out. I know I can work backwards and find a
parent from its child by decoding its key. But my app can obviously go
the other way and it would make my life easier if I could too. Can
anyone help?

Thanks,
Dan

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[appengine-java] Re: is google app engine a real-time cloud?

[Enrique Perez]

Ok, so I will take a shot at this one

Alot of the non-SQL datastores emerging are implementing consistency
models known as "Eventually Consistent".  SimpleDb at Amazon is one of
these.  The idea is that when your thread of execution writes to the
datastore your write call returns back from the datastore write call
fairly quickly and if you tried to read back your newly written entity
you may or may not get it back.  But, eventually you would, maybe some
number of seconds later. There are many systems we use this
consistency model today.  Email, for example

Per Ryan Barrett, in Google I/O 2008 - Under the hood of datastore, he
described App Engine datastore as "Strongly Consistent".  Other well
known "Strongly Consistent" systems you might have used are relational
databases or file systems.  When you write an entity to the App Engine
datastore, the call blocks and only returns after the entity is
written to the entity table, and all indexes rows are written or
updated.  Within the same thread of execution, if you were to try to
read back your entity you would always get it back.

Now, there is another factor at play here which I have observed with
apps running in production. If you running your primary browser doing
datastore writes, you can open a second browser on different machine
and bring up your dataviewer. After you perform a write on browser #1,
you can refresh your second browser which is pointing to the data
viewer.  Quite often you will not see the results of write from
browser #1 until some seconds later.  I assumed that this was related
to the fact that the second browser was hitting a different data
center, or datastore clustor, and the replication from datastore
clustor #1 to datastore clustor #2 had not yet occurred.  In Google I/
O - 2009 - Weekend Projects - Barrett describes App Engine Multi-
homing techniqes.  App Engine datastore is using Master-Slave
replication system which is I believe explaining why my browser #2
takes some seconds to see the change.

However, even with this behavior related to Multi-homing Master-Slave
replication in place, the App Engine datastore is still described as
"Strongly Consistent".  If one were to implement Multi-Homing Master-
Slave replication with relational database technology I believe one
would still see the type of behavior I have just described.

Hopefully this make sense and I have explained this correctly.  If I
have gotten something wrong I would love to get a better understanding
of this.  I love to hear any more detailed information on how things
work under the hood from those that know ...

Thanks
Enrique Perez
Austin, Texas




On Feb 2, 8:09 pm, smile laugh  wrote:
> hello everyone
>
> someone said that cloud computing is not real-time platform.
>
> that is to say, if you insert a record into cloud(such as bigtable),
> and then if you query the record immediately , maybe no rowset
> returned.
> because in a cloud platform, a record is store in lots of server , at
> that time when you query that inserted record , some server may not be
> synchronized , and your query is done in those server
>
> is that true?
>
> thanks in advance

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[appengine-java] Re: Memcache data life cycle

[Max]

Thanks, I have done some experiments which support your point.

On Jan 17, 7:11 pm, Qian Qiao  wrote:
> On Sun, Jan 17, 2010 at 19:04, Max  wrote:
> > Hi GAE gurus,
>
> > Is there anyone who can tell me the life-cycle of data cached in
> > memcache?
>
> > I found those cached in memcache won't be expired even I re-deploy my
> > project. Does that means I can use it like a datastore without
> > transaction support?
>
> > Best regards,
> > Max
>
> No, you can't use it as a datastore, it is only a cache as the name
> suggests, even if you set the cache entries to never expire, it might
> end up being replaced when the underlying system thinks necessary.
>
> -- Joe
>
> --
> Two things that are infinite, the universe and my stupidity, and I'm
> not sure about the universe.

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[appengine-java] Performance of count entity

[Max]

Hi,

I am designing my data model and planning to use following KeysOnly
query to perform a count(*) with some filter conditions by a daily
cron job.

FetchOptions fetchOptions = FetchOptions.Builder.withOffset(0).limit
(Integer.MAX_VALUE);
DatastoreService.prepare(query).asList(fetchOptions).size();

Here are my questions:
1, if I use an ancestor query (in a transaction) over an entity group
with around 1 million records of this kind, how is the performance?

2, if I use an ancestor query without a transaction (to avoid locking
whole entity group), how is the performance?

3, if I use a normal query over around 1k entity groups with around 10
million records of this kind, how is the performance?

Many thanks.

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[appengine-java] Re: Can't run the Java version of GAE.

[seleronm]

Hi.

Though it might be unrelated

Please refer to the following links
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=560044


Please Try.
thanks.


On 2月3日, 午前4:23, Don Schwarz  wrote:
> Sorry, I don't really have any theories.  No one else has ever
> reported this, so lets start with what makes your machine unique.
>
> What JRE are you running?  Can you try a Sun 1.5 or 1.6 VM if you're
> not already using one?
>
> Is there anything special about the networking on your machine?  IPv6
> support?  Multiple IPv4 networks?  etc.
>
> Does specifying an alternate port with -p work?
>
> On Fri, Jan 29, 2010 at 1:36 PM, Tordek  wrote:
> > Tordek wrote:
>
> >> I wanted to try out Clojure in GAE, so I downloaded the Java SDK, but
> >> I can't run the demo apps: I get this error.
>
> >> ~/src/JavaGae$ ./appengine-java-sdk-1.3.0/bin/dev_appserver.sh
> >> appengine-java-sdk-1.3.0/demos/guestbook/war/
> >> 26-Jan-2010 19:00:50 com.google.apphosting.utils.jetty.JettyLogger
> >> warn
> >> WARNING: failed selectchannelconnec...@127.0.0.1:8080
> >> java.net.SocketException: Invalid argument
> >>        at sun.nio.ch.Net.bind(Native Method)
> >>        at sun.nio.ch.ServerSocketChannelImpl.bind
> >> (ServerSocketChannelImpl.java:119)
> >>        at sun.nio.ch.ServerSocketAdaptor.bind
> >> (ServerSocketAdaptor.java:59)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.open
> >> (SelectChannelConnector.java:211)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
> >> (SelectChannelConnector.java:309)
> >>        at org.mortbay.component.AbstractLifeCycle.start
> >> (AbstractLifeCycle.java:40)
> >>        at org.mortbay.jetty.Server.doStart(Server.java:228)
> >>        at org.mortbay.component.AbstractLifeCycle.start
> >> (AbstractLifeCycle.java:40)
> >>        at
>
> >> com.google.appengine.tools.development.JettyContainerService.startContainer
> >> (JettyContainerService.java:188)
> >>        at
> >> com.google.appengine.tools.development.AbstractContainerService.startup
> >> (AbstractContainerService.java:120)
> >>        at
> >> com.google.appengine.tools.development.DevAppServerImpl.start
> >> (DevAppServerImpl.java:217)
> >>        at com.google.appengine.tools.development.DevAppServerMain
> >> $StartAction.apply(DevAppServerMain.java:162)
> >>        at com.google.appengine.tools.util.Parser$ParseResult.applyArgs
> >> (Parser.java:48)
> >>        at
> >> com.google.appengine.tools.development.DevAppServerMain.
> >> (DevAppServerMain.java:113)
> >>        at com.google.appengine.tools.development.DevAppServerMain.main
> >> (DevAppServerMain.java:89)
> >> 26-Jan-2010 19:00:50 com.google.apphosting.utils.jetty.JettyLogger
> >> warn
> >> WARNING: failed ser...@7eb1cc87
> >> java.net.SocketException: Invalid argument
> >>        at sun.nio.ch.Net.bind(Native Method)
> >>        at sun.nio.ch.ServerSocketChannelImpl.bind
> >> (ServerSocketChannelImpl.java:119)
> >>        at sun.nio.ch.ServerSocketAdaptor.bind
> >> (ServerSocketAdaptor.java:59)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.open
> >> (SelectChannelConnector.java:211)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
> >> (SelectChannelConnector.java:309)
> >>        at org.mortbay.component.AbstractLifeCycle.start
> >> (AbstractLifeCycle.java:40)
> >>        at org.mortbay.jetty.Server.doStart(Server.java:228)
> >>        at org.mortbay.component.AbstractLifeCycle.start
> >> (AbstractLifeCycle.java:40)
> >>        at
>
> >> com.google.appengine.tools.development.JettyContainerService.startContainer
> >> (JettyContainerService.java:188)
> >>        at
> >> com.google.appengine.tools.development.AbstractContainerService.startup
> >> (AbstractContainerService.java:120)
> >>        at
> >> com.google.appengine.tools.development.DevAppServerImpl.start
> >> (DevAppServerImpl.java:217)
> >>        at com.google.appengine.tools.development.DevAppServerMain
> >> $StartAction.apply(DevAppServerMain.java:162)
> >>        at com.google.appengine.tools.util.Parser$ParseResult.applyArgs
> >> (Parser.java:48)
> >>        at
> >> com.google.appengine.tools.development.DevAppServerMain.
> >> (DevAppServerMain.java:113)
> >>        at com.google.appengine.tools.development.DevAppServerMain.main
> >> (DevAppServerMain.java:89)
> >> java.net.SocketException: Invalid argument
> >>        at sun.nio.ch.Net.bind(Native Method)
> >>        at sun.nio.ch.ServerSocketChannelImpl.bind
> >> (ServerSocketChannelImpl.java:119)
> >>        at sun.nio.ch.ServerSocketAdaptor.bind
> >> (ServerSocketAdaptor.java:59)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.open
> >> (SelectChannelConnector.java:211)
> >>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
> >> (SelectChannelConnector.java:309)
> >>        at org.mortbay.component.AbstractLifeCycle.start
> >> (AbstractLifeCycle.java:40)
> >>        at org.mortbay.jetty.Server.doStart(Server.java:228)
> >>        at org.mortbay.component.AbstractLifeCycle.

Re: [appengine-java] Two ManyToOne relationships in one class

[Ikai L (Google)]

The explanation for the exception is in the exception text itself. Each
entity's key contains the ancestor information for that entity:

http://code.google.com/appengine/articles/storage_breakdown.html

"A path is
a concatenation of entity keys. Every path begins with the key of the root
entity (which may be the current entity itself) in the current entity group.
If the current entity is not the root, then the key of each ancestor is
appended to the path, from top to bottom, until the current entity's key is
appended."

That is, if you persist Venue before persisting its parent, you get the key
Venue(ID). Were you to persist the ancestors first, you would get an
unencoded key of Person(PERSON_ID)/TIP(TIP_ID)/Venue(VENUE_ID).

You've got a few options here:

1. Store the Key instead. This won't force the entities into an entity group
relationship. The tradeoff here is that you lose the ability to perform
transactions on these entities.

2. Restructure your entity groups. Remember that these are in a tree-like
hierarchy with a root entity and child entities. This limits the way you can
design one-to-many relationships without using keys, as entities cannot be
part of multiple entity groups. Our docs on this are here:
http://code.google.com/appengine/docs/java/datastore/relationships.html

On Sun, Jan 31, 2010 at 6:28 AM, Wong  wrote:

>
> In my application I have bi-directional one-to-many relationship
> between Venue and Tip.
>
> @Entity
> public class Venue implements Serializable {
>@Id
>@GeneratedValue(strategy = GenerationType.IDENTITY)
>private Key key;
>
>
>@OneToMany(cascade = CascadeType.ALL, mappedBy="venue")
>
>private List tips;
>
>
> @Entity
> public class Tip implements Serializable {
>@Id
>@GeneratedValue(strategy = GenerationType.IDENTITY)
>private Key key;
>
>private Integer version;
>
>
>
>@ManyToOne(fetch = FetchType.LAZY)
>private Venue venue;
>
>
> I have venue object persisted and then tip is added to the venue. I
> don't any any problem in doing this.
>
> Venue venue = venueService.find(key);
> venue.addTip(tip);
> venueService.merge(venue);
>
>
> Then I expand the relationship to have another bi-directional one-to-
> many relationship between Person and Tip. Tip is posted by a Person
> and for a Venue. One Person can post more than one Tips for a Venue.
>
> @Entity
> public class Tip implements Serializable {
>@Id
>@GeneratedValue(strategy = GenerationType.IDENTITY)
>private Key key;
>
>@ManyToOne(fetch = FetchType.LAZY)
>private Venue venue;
>
>@ManyToOne(fetch = FetchType.LAZY)
>private Person postedBy;
>
>
> @Entity
> public class Person implements Serializable, UserDetails {
>@Id
>@GeneratedValue(strategy = GenerationType.IDENTITY)
>private Key key;
>
>@OneToMany(cascade = CascadeType.ALL, mappedBy="postedBy")
>private List tips;
>
>
> Venue venue = venueService.find(key);
> Person person = personService.find(userId);
> venue.addTip(tip);
> person.addTip(tip);
> venueService.merge(venue);
>
>
> I am getting the following error:
>
> Detected attempt to establish Person(29)/Tip(125) as the parent of
> Venue(2) but the entity identified by Venue(2) has already been
> persisted without a parent. A parent cannot be established or changed
> once an object has been persisted.
> org.datanucleus.store.appengine.FatalNucleusUserException: Detected
> attempt to establish Person(29)/Tip(125) as the parent of Venue(2) but
> the entity identified by Venue(2) has already been persisted without a
> parent. A parent cannot be established or changed once an object has
> been persisted. at
>
> org.datanucleus.store.appengine.DatastoreRelationFieldManager.checkForParentSwitch
> (DatastoreRelationFieldManager.java:204) at
> org.datanucleus.store.appengine.DatastoreRelationFieldManager
> $1.setObjectViaMapping(DatastoreRelationFieldManager.java:125) at
> org.datanucleus.store.appengine.DatastoreRelationFieldManager$1.apply
> (DatastoreRelationFieldManager.java:104) at
>
> org.datanucleus.store.appengine.DatastoreRelationFieldManager.storeRelations
> (DatastoreRelationFieldManager.java:78) at
> org.datanucleus.store.appengine.DatastoreFieldManager.storeRelations
> (DatastoreFieldManager.java:812) at
>
> org.datanucleus.store.appengine.DatastorePersistenceHandler.insertPostProcess
> (DatastorePersistenceHandler.java:288) at
> org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObjects
> (DatastorePersistenceHandler.java:241) at
> org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObject
> (DatastorePersistenceHandler.java:225) at
> org.datanucleus.state.JDOStateManagerImpl.internalMakePersistent
> (JDOStateManagerImpl.java:3185) at
> org.datanucleus.state.JDOStateManagerImpl.flush
> (JDOStateManagerImpl.java:4513) at
> org.datanucleus

[appengine-java] is google app engine a real-time cloud?

[smile laugh]

hello everyone

someone said that cloud computing is not real-time platform.

that is to say, if you insert a record into cloud(such as bigtable),
and then if you query the record immediately , maybe no rowset
returned.
because in a cloud platform, a record is store in lots of server , at
that time when you query that inserted record , some server may not be
synchronized , and your query is done in those server

is that true?

thanks in advance

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[appengine-java] Re: Object state from a query

[Brandon]

Thx. Can the state only be determined at runtime, or there is a
general rule? I appreciate if you can let me know whether each match
is retrieved in an independent transaction.

Thx again.

On Feb 2, 12:04 am, datanucleus  wrote:
> JDOHelper.getObjectState(obj) ?

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[appengine-java] Re: Restrict which google accounts can access the app

[hendrix.jason]

I think this is what you are looking for:
http://code.google.com/appengine/docs/java/config/webxml.html#Security_and_Authentication


On Jan 31, 2:55 pm, Scott  wrote:
> I read that you can make people login to their google account in order
> gain access to your app, but is there a way to restrict access to only
> certain google account??

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[appengine-java] Re: Can't compile Guestbook demo modified as in the video

[SD]

Any deployable demo involving the datastore?
So far was able to deploy only hello-world-type applications, no luck
with the datastore-linked guestbook.

Tried to deploy code from:
http://googleappengine.googlecode.com/svn›
trunk›
java›
demos›
jdoexamples

but it did not work either.

Kept modifying the code and was getting different 500 errors (once it
was 403),
ranging from C:\Users\SD\AppData\Local\Temp
\Jetty_127_0_0_1__war-g0qk00\jsp\org\apache\jsp
\guestbook_jsp.java:162: 'catch' without 'try'
to
java.lang.ExceptionInInitializerError
at org.apache.jsp.guestbook_jsp._jspService(guestbook_jsp.java:62)
to
java.lang.NoClassDefFoundError: Could not initialize class
com.google.guestbook.PMF


This is what I get when trying to deploy.

Unable to update:
com.google.appengine.tools.admin.JspCompilationException: Failed to
compile the generated JSP java files.
at com.google.appengine.tools.admin.Application.compileJavaFiles
(Application.java:416)
at com.google.appengine.tools.admin.Application.compileJsps
(Application.java:376)
at com.google.appengine.tools.admin.Application.createStagingDirectory
(Application.java:252)
at com.google.appengine.tools.admin.AppAdminImpl.update
(AppAdminImpl.java:54)
at com.google.appengine.eclipse.core.proxy.AppEngineBridgeImpl.deploy
(AppEngineBridgeImpl.java:271)
at
com.google.appengine.eclipse.core.deploy.DeployProjectJob.runInWorkspace
(DeployProjectJob.java:148)
at org.eclipse.core.internal.resources.InternalWorkspaceJob.run
(InternalWorkspaceJob.java:38)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)


Any insight? Thanks a lot,
SD

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Re: [appengine-java] dynamic class load

[Ikai L (Google)]

Yes. Run your server using "Debug". Eclipse will automatically compile your
classes on save.

The only exception is certain types of changes to classes that need to be
enhanced after compilation. Eclipse will prompt you to restart.

On Tue, Feb 2, 2010 at 4:04 PM, javaness  wrote:

> Hi;
>
> I am trying Java on Eclipse by App engine plugin.
>
> Is it possible to dynamically load classes? (maybe hot-swapping is the
> correct term)
>
> In an another project, I use Jetty plugin of Maven, and whenever I
> compile a java class, Jetty automically loads it.
> So no restart is needed on code modifications.
>
> Is that possible on Eclipse configuration of App Engine.
>
> Thanks;
>
> --
> You received this message because you are subscribed to the Google Groups
> "Google App Engine for Java" group.
> To post to this group, send email to
> google-appengine-j...@googlegroups.com.
> To unsubscribe from this group, send email to
> google-appengine-java+unsubscr...@googlegroups.com
> .
> For more options, visit this group at
> http://groups.google.com/group/google-appengine-java?hl=en.
>
>


-- 
Ikai Lan
Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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[appengine-java] dynamic class load

[javaness]

Hi;

I am trying Java on Eclipse by App engine plugin.

Is it possible to dynamically load classes? (maybe hot-swapping is the
correct term)

In an another project, I use Jetty plugin of Maven, and whenever I
compile a java class, Jetty automically loads it.
So no restart is needed on code modifications.

Is that possible on Eclipse configuration of App Engine.

Thanks;

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[appengine-java] Re: memcache SerializationException

[chiappone]

Is it even possible to use memcache with GWT on the server side?  I am
wondering if I am even able to do this?

On Feb 1, 1:56 pm, chiappone  wrote:
> I have hit the wall in trying to figure out what I am doing wrong in
> my GAE GWT application.  I am trying to use memcache to get a list of
> serializable objects out of the cache in a service.  It seems to put
> them fine, and I can see them being pulled from cache in the debugger
> but I end up getting the following exception:
>
> This is the call to pull the object out of cache:
> List ecDevices = (List) cache.findInCache(partitionKey);
>                 if(ecDevices != null && ecDevices.size() > 0){
>                         log.info("Returning devices from cache");
>                         return ecDevices;
>                 }...
>
> SEVERE: [1265057364142000] javax.servlet.ServletContext log: Exception
> while dispatching incoming RPC call
> com.google.gwt.user.client.rpc.SerializationException:
> java.lang.reflect.InvocationTargetException
>         at
> com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.seriali 
> zeWithCustomSerializer
> (ServerSerializationStreamWriter.java:760)
>         at
> com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.seriali 
> zeImpl
> (ServerSerializationStreamWriter.java:723)
>         at
> com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.seriali ze
> (ServerSerializationStreamWriter.java:612)
>         at
> com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.write 
> Object
> (AbstractSerializationStreamWriter.java:129)
>         at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter
> $ValueWriter$8.write(ServerSerializationStreamWriter.java:152)
>         at
> com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.seriali 
> zeValue
> (ServerSerializationStreamWriter.java:534)
>         at com.google.gwt.user.server.rpc.RPC.encodeResponse(RPC.java:609)
>         at com.google.gwt.user.server.rpc.RPC.encodeResponseForSuccess
> (RPC.java:467)
>         at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse
> (RPC.java:564)
>         at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall
> (RemoteServiceServlet.java:188)
>         at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost
> (RemoteServiceServlet.java:224)
>         at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost
> (AbstractRemoteServiceServlet.java:62)
>         at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
>         at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
>         at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
> 487)
>         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> (ServletHandler.java:1093)
>         at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter
> (ServeBlobFilter.java:51)
>         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> (ServletHandler.java:1084)
>         at
> com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter
> (TransactionCleanupFilter.java:43)
>         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> (ServletHandler.java:1084)
>         at com.google.appengine.tools.development.StaticFileFilter.doFilter
> (StaticFileFilter.java:121)
>         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> (ServletHandler.java:1084)
>         at org.mortbay.jetty.servlet.ServletHandler.handle
> (ServletHandler.java:360)
>         at org.mortbay.jetty.security.SecurityHandler.handle
> (SecurityHandler.java:216)
>         at org.mortbay.jetty.servlet.SessionHandler.handle
> (SessionHandler.java:181)
>         at org.mortbay.jetty.handler.ContextHandler.handle
> (ContextHandler.java:712)
>         at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
> 405)
>         at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle
> (DevAppEngineWebAppContext.java:70)
>         at org.mortbay.jetty.handler.HandlerWrapper.handle
> (HandlerWrapper.java:139)
>         at com.google.appengine.tools.development.JettyContainerService
> $ApiProxyHandler.handle(JettyContainerService.java:352)
>         at org.mortbay.jetty.handler.HandlerWrapper.handle
> (HandlerWrapper.java:139)
>         at org.mortbay.jetty.Server.handle(Server.java:313)
>         at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
> 506)
>         at org.mortbay.jetty.HttpConnection$RequestHandler.content
> (HttpConnection.java:844)
>         at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:644)
>         at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
>         at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381)
>         at org.mortbay.io.nio.SelectChannelEndPoint.run
> (SelectChannelEndPoint.java:396)
>         at org.mortbay.thread.BoundedThreadPool$PoolThread.run
> (Boun

[appengine-java] Need to update the type of primary key on existing objects in GAE Java

[shaz]

Hi,

I am building a web app using GAE Java. I have a class that uses a
Long ID as its primary key.

I now want to create a new class that would be the parent class to
this original class (a one to many relationship) however the children
that already exist need to have a primary key of type "key", not the
Long ID I have now.

What is the best way to change the primary key to be type "key"
instead of long for the existing persisted entities? Should I create a
new class with primary key of type "key" and instantiate and persist
new objects that copy the field values from the old ones? Or can I
somehow just update the existing class?

Thanks

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Re: [appengine-java] Can't use hessian with appengine

[Jeff Schnitzer]

FWIW, it's actually quite easy to check out Resin trunk (which holds
the hessian source code), make the patch, build with ant, and get a
hessian.jar.

Hessian works quite beautifully on appengine.  I wish I had an
asynchronous ObjectiveC hessian client so I could ditch my tediously
duplicated JAX-RS api.

Jeff

On Tue, Feb 2, 2010 at 1:19 PM, Olemis Lang  wrote:
> On Wed, May 20, 2009 at 6:06 AM, Konstantin Solomatov
>  wrote:
>>
>> Hello,
>>
>> I wanted to use Hessian in my appengine application 
>> http://hessian.caucho.com/
>> When I test code locally everything works well. When I deploy to the
>> app engine, things go awry. If I send a request to there I get the
>> following exception:
>>
>> Exception in thread "main"
>> com.caucho.hessian.client.HessianConnectionException: 501:
>> java.io.IOException: Server returned HTTP response code: 501 for URL
>>
>> How can I find out where the problem is? What isn't implemented there?
>>
>
> Probably related to this [1]_ ?
>
> .. [1] Webservice on Google App Engine - Google App Engine for Java ...
>        
> (http://groups.google.com/group/google-appengine-java/browse_thread/thread/0068bf08c5fd3fef/4edb06eb6f316689?lnk=raot)
>
> --
> Regards,
>
> Olemis.
>
> Blog ES: http://simelo-es.blogspot.com/
> Blog EN: http://simelo-en.blogspot.com/
>
> Featured article:
> Sobrepasa las 1000 descargas el módulo TracGViz (>300 desde PyPI) -
> http://feedproxy.google.com/~r/simelo-es/~3/DdGeJirDqUk/sobrepasa-las-1000-descargas-el-modulo.html
>
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>
>

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Re: [appengine-java] Re: Unsupported method while parsing expression:

[Ikai L (Google)]

Oy, this is what I get for not running code before posting it. Good looking
out.

On Tue, Feb 2, 2010 at 1:06 AM, datanucleus wrote:

> >query.setFilter("aliases == alias");
>
> That is invalid JDOQL syntax; the spec is the spec and JDOQL uses Java
> syntax.
> If you have a collection field then the filter should be
>
> aliases.contains(:alias)
>
> The poster put the colon in front of a field name (wrong), and
> declared a parameter as a variable (wrong).
>
> --
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>
>


-- 
Ikai Lan
Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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[appengine-java] Re: non-deterministic datastore behaviour while unit testing

[Markus Scheidgen]

No, no caught or uncaught exception what so ever.

I tried to create a very simple version of what I was doing. The
simplest example, I could imagine, is the following:

public class OwnedRelationships extends LocalServiceTestCase {

@PersistenceCapable(identityType = IdentityType.APPLICATION)
static class Parent {

@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@PrimaryKey
Key key;

@Persistent
Child child;

@Persistent
String value;
}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
static class Child {
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@PrimaryKey
Key key;

@Persistent
String value;
}

public void testOneToOne() {
PersistenceManager pm = PMF.get().getPersistenceManager();

Parent parent = new Parent();
Child child = new Child();
parent.value = "parent1";
child.value = "child1";
parent.child = child;

try {
pm.makePersistent(parent);
} finally {
pm.close();
}

pm = PMF.get().getPersistenceManager();
Parent controlParent = null;
try {
controlParent = pm.getObjectById(Parent.class, 
parent.key);
} finally {
pm.close();
}

assertTrue(controlParent.child != null);  // some times
controlParent.child is null, sometimes it is not
assertTrue(controlParent.child.equals("child1"));
}
}

This simple example, actually never works. But I think it should work,
shouldn't it?

The next example, is the actual code that caused the arbitrary
behaviour. Sometimes it works, sometimes it doesn't. Once compiled, it
behaves the same way on every run. But you change it a little bit,
maybe comment some unimportant line, and it stops working.

public class DBTest extends LocalServiceTestCase {

public void testPlayerWithComments() {
PlayerDB player = PlayerDB.createDefault("test1");
CommentDB comment = CommentDB.createDefault();
comment.setAuthor(player);
player.getComments().add(comment);

PersistenceManager pm = PMF.get().getPersistenceManager();
try {
pm.makePersistent(player);
} finally {
pm.close();
}
pm = PMF.get().getPersistenceManager();
try {
PlayerDB controlPlayerObject = 
pm.getObjectById(PlayerDB.class,
"test1");
assertTrue("comment not persistet in player",
controlPlayerObject.getComments().size() == 1);  // the list is
sometimes empty, even though it should contain one comment

CommentDB controlCommentObject = 
pm.getObjectById(CommentDB.class,
controlPlayerObject.getComments().get(0).getKey());
assertTrue("cannot navigate to player",

controlCommentObject.getAuthor(pm).getId().equals
(controlPlayerObject.getId()));

Collection comments = 
(Collection)pm.newQuery
(CommentDB.class).execute();
assertTrue("comment not loadable with query", 
comments.size() ==
1);
} finally {
pm.close();
}
}
}

@PersistenceCapable(identityType=IdentityType.APPLICATION)
public class CommentDB {

public static CommentDB createDefault() {
CommentDB result = new CommentDB();
result.setComment("");
return result;
}

private CommentDB() {

}

@PrimaryKey
@Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY)
private Key key;

@Persistent
private Text comment;

@Persistent
private String author;

@Persistent
private Key owner;

public String getComment() {
return comment.getValue();
}

public void setComment(String comment) {
this.comment = new Text(comment);
}

public PlayerDB getAuthor(PersistenceManager pm) {
return pm.getObjectById(PlayerDB.class, author);
}

public void setAuthor(PlayerDB author) {
this.author = author.getId();
}

public  T getOwner(PersistenceManager pm, Class ownerType) {
return pm.getObjectById(ownerType, owner);
}

public void setOwner(Key owner) {
this.owner = owner;
}

pub

Re: [appengine-java] Can't use hessian with appengine

[Olemis Lang]

On Wed, May 20, 2009 at 6:06 AM, Konstantin Solomatov
 wrote:
>
> Hello,
>
> I wanted to use Hessian in my appengine application http://hessian.caucho.com/
> When I test code locally everything works well. When I deploy to the
> app engine, things go awry. If I send a request to there I get the
> following exception:
>
> Exception in thread "main"
> com.caucho.hessian.client.HessianConnectionException: 501:
> java.io.IOException: Server returned HTTP response code: 501 for URL
>
> How can I find out where the problem is? What isn't implemented there?
>

Probably related to this [1]_ ?

.. [1] Webservice on Google App Engine - Google App Engine for Java ...

(http://groups.google.com/group/google-appengine-java/browse_thread/thread/0068bf08c5fd3fef/4edb06eb6f316689?lnk=raot)

-- 
Regards,

Olemis.

Blog ES: http://simelo-es.blogspot.com/
Blog EN: http://simelo-en.blogspot.com/

Featured article:
Sobrepasa las 1000 descargas el módulo TracGViz (>300 desde PyPI) -
http://feedproxy.google.com/~r/simelo-es/~3/DdGeJirDqUk/sobrepasa-las-1000-descargas-el-modulo.html

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[appengine-java] Eclipse GAE plugin problem with Datanucleus enrichment

[Joe Hudson]

Hello,

I am using the Google App Engine Eclipse plugin and get an error when
I save a Java class with a get(String) method.

The enhancer is throwing a NullPointerException. I have added the
transient annotation and don't know what else I can do to avoid this
issue. Can anyobody please give me some advice?

I am using datanucleus-jpa-1.1.5.jar

I also posted this to the datanucleus forum but there doesn't seem to
be too much activity there so I was hoping I would get some ideas here
as well.  http://www.jpox.org/servlet/forum/viewthread_thread,5954#31824

Thank you very much.

The referenced code is below:

@Entity
public class TestEntity implements Serializable {

private String dummyProperty;

public String getDummyProperty() {
return dummyProperty;
}

public void setDummyProperty(String dummyProperty) {
this.dummyProperty = dummyProperty;
}

@Transient
public Object get(String key) {
return null;
}
}


And, here is the stack trace:

DataNucleus Enhancer (version 1.1.4) : Enhancement of classes
Errors were encountered when loading the specified MetaData files and
classes. See the nested exceptions for details
Feb 2, 2010 1:45:24 PM org.datanucleus.enhancer.DataNucleusEnhancer
main
SEVERE: DataNucleus Enhancer completed with an error. Please review
the enhancer log for full details. Some classes may have been enhanced
but some caused errors
Errors were encountered when loading the specified MetaData files and
classes. See the nested exceptions for details
org.datanucleus.exceptions.NucleusUserException: Errors were
encountered when loading the specified MetaData files and classes. See
the nested exceptions for details
at org.datanucleus.metadata.MetaDataManager.loadClasses
(MetaDataManager.java:426)
at org.datanucleus.enhancer.DataNucleusEnhancer.getFileMetadataForInput
(DataNucleusEnhancer.java:743)
at org.datanucleus.enhancer.DataNucleusEnhancer.enhance
(DataNucleusEnhancer.java:545)
at org.datanucleus.enhancer.DataNucleusEnhancer.main
(DataNucleusEnhancer.java:1252)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke
(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:
57)
at com.google.appengine.tools.enhancer.Enhance.(Enhance.java:60)
at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:41)
Caused by: java.lang.NullPointerException
at
org.datanucleus.jpa.metadata.JPAAnnotationReader.processMemberAnnotations
(JPAAnnotationReader.java:8
53)
at
org.datanucleus.metadata.annotations.AbstractAnnotationReader.getMetaDataForClass
(AbstractAnnotation
Reader.java:159)
at
org.datanucleus.metadata.annotations.AnnotationManagerImpl.getMetaDataForClass
(AnnotationManagerImpl
.java:136)
at org.datanucleus.metadata.MetaDataManager.loadAnnotationsForClass
(MetaDataManager.java:2278)
at org.datanucleus.metadata.MetaDataManager.loadClasses
(MetaDataManager.java:385)
... 10 more
Nested Throwables StackTrace:
DataNucleus Enhancer completed with an error. Please review the
enhancer log for full details. Some classes may have been enhanced but
some caused errors
java.lang.NullPointerException
DataNucleus Enhancer completed and no classes were enhanced. Consult
the log for full details
at
org.datanucleus.jpa.metadata.JPAAnnotationReader.processMemberAnnotations
(JPAAnnotationReader.java:8
53)
at
org.datanucleus.metadata.annotations.AbstractAnnotationReader.getMetaDataForClass
(AbstractAnnotation
Reader.java:159)
at
org.datanucleus.metadata.annotations.AnnotationManagerImpl.getMetaDataForClass
(AnnotationManagerImpl
.java:136)
at org.datanucleus.metadata.MetaDataManager.loadAnnotationsForClass
(MetaDataManager.java:2278)
at org.datanucleus.metadata.MetaDataManager.loadClasses
(MetaDataManager.java:385)
at org.datanucleus.enhancer.DataNucleusEnhancer.getFileMetadataForInput
(DataNucleusEnhancer.java:743)
at org.datanucleus.enhancer.DataNucleusEnhancer.enhance
(DataNucleusEnhancer.java:545)
at org.datanucleus.enhancer.DataNucleusEnhancer.main
(DataNucleusEnhancer.java:1252)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke
(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:
57)
at com.google.appengine.tools.enhancer.Enhance.(Enhance.java:60)
at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:41)

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Re: [appengine-java] non-deterministic datastore behaviour while unit testing

[John Patterson]

You say that you experience this when debugging - do you see any  
exceptions being thrown?  One common exception I see during long  
debugging sessions is "Handle 7 found" or similar.  But these do not  
occur on the production servers.



On 3 Feb 2010, at 02:52, Ikai L (Google) wrote:

Can you post test cases that produce non-deterministic behavior? If  
this is reproducible, please create an issue with the entities and  
test cases in question and let us know:


http://code.google.com/p/googleappengine/issues/

On Tue, Feb 2, 2010 at 6:48 AM, Markus Scheidgen > wrote:

Hi,

I use junit to unit test my app according to the "Unit Testing With
Local Service Implementations" tutorial. Once I use owned
relationships within my data-model, the datastore sometimes behaves
unexpected. Objects and links stored in the datastore, sometimes can
not be read from the data store. The data store behaves as if those
objects or links have never been stored. In some runs everything
behaves like it ought to be, in other runs it doesn't. Especially when
I use the eclipse debug mode, the test-cases often have different
outcomes than running them without a debugger.

What troubles me the most, is the non-deterministic scheme. Sometimes
it works, sometimes it doesn't.

So far, I only had this during unit testing. When using the
development server or the cloud, everything worked out as it should.

Does anybody had experienced something similar? Any hind? Maybe there
is some common pit-fall in using the jdo data store or owned
relationships (even though I use it along the documentation and
tutorials).

Thanks,
Markus

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--
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Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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Re: [appengine-java] non-deterministic datastore behaviour while unit testing

[Ikai L (Google)]

Can you post test cases that produce non-deterministic behavior? If this is
reproducible, please create an issue with the entities and test cases in
question and let us know:

http://code.google.com/p/googleappengine/issues/

On Tue, Feb 2, 2010 at 6:48 AM, Markus Scheidgen <
markus.scheid...@googlemail.com> wrote:

> Hi,
>
> I use junit to unit test my app according to the "Unit Testing With
> Local Service Implementations" tutorial. Once I use owned
> relationships within my data-model, the datastore sometimes behaves
> unexpected. Objects and links stored in the datastore, sometimes can
> not be read from the data store. The data store behaves as if those
> objects or links have never been stored. In some runs everything
> behaves like it ought to be, in other runs it doesn't. Especially when
> I use the eclipse debug mode, the test-cases often have different
> outcomes than running them without a debugger.
>
> What troubles me the most, is the non-deterministic scheme. Sometimes
> it works, sometimes it doesn't.
>
> So far, I only had this during unit testing. When using the
> development server or the cloud, everything worked out as it should.
>
> Does anybody had experienced something similar? Any hind? Maybe there
> is some common pit-fall in using the jdo data store or owned
> relationships (even though I use it along the documentation and
> tutorials).
>
> Thanks,
> Markus
>
> --
> You received this message because you are subscribed to the Google Groups
> "Google App Engine for Java" group.
> To post to this group, send email to
> google-appengine-j...@googlegroups.com.
> To unsubscribe from this group, send email to
> google-appengine-java+unsubscr...@googlegroups.com
> .
> For more options, visit this group at
> http://groups.google.com/group/google-appengine-java?hl=en.
>
>


-- 
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Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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Re: [appengine-java] My application stopped working

[Ikai L (Google)]

This issue should have been resolved:
http://groups.google.com/group/google-appengine-downtime-notify/browse_thread/thread/7fb8a39149de3b55

Please
let us know if you are continuing to be affected.

On Tue, Feb 2, 2010 at 6:40 AM, Stéphane Traumat  wrote:

> Hello... My application as running well since some days :
> http://www.quatuo.com/
> ( quatuo-www )
>
> Today, i connect and i see a 500 error message... no Idea why...
> nothing in the logs... I tried to empty queues, redeploy and all...
> but still nothing is working :(
> I need help as peoples just can't use the service anymore.. and i have
> no idea why.
>
> Regards
>
> --
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> "Google App Engine for Java" group.
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> google-appengine-j...@googlegroups.com.
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> .
> For more options, visit this group at
> http://groups.google.com/group/google-appengine-java?hl=en.
>
>


-- 
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Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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Re: [appengine-java] Can't run the Java version of GAE.

[Don Schwarz]

Sorry, I don't really have any theories.  No one else has ever
reported this, so lets start with what makes your machine unique.

What JRE are you running?  Can you try a Sun 1.5 or 1.6 VM if you're
not already using one?

Is there anything special about the networking on your machine?  IPv6
support?  Multiple IPv4 networks?  etc.

Does specifying an alternate port with -p work?

On Fri, Jan 29, 2010 at 1:36 PM, Tordek  wrote:
> Tordek wrote:
>>
>> I wanted to try out Clojure in GAE, so I downloaded the Java SDK, but
>> I can't run the demo apps: I get this error.
>>
>> ~/src/JavaGae$ ./appengine-java-sdk-1.3.0/bin/dev_appserver.sh
>> appengine-java-sdk-1.3.0/demos/guestbook/war/
>> 26-Jan-2010 19:00:50 com.google.apphosting.utils.jetty.JettyLogger
>> warn
>> WARNING: failed selectchannelconnec...@127.0.0.1:8080
>> java.net.SocketException: Invalid argument
>>        at sun.nio.ch.Net.bind(Native Method)
>>        at sun.nio.ch.ServerSocketChannelImpl.bind
>> (ServerSocketChannelImpl.java:119)
>>        at sun.nio.ch.ServerSocketAdaptor.bind
>> (ServerSocketAdaptor.java:59)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.open
>> (SelectChannelConnector.java:211)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
>> (SelectChannelConnector.java:309)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at org.mortbay.jetty.Server.doStart(Server.java:228)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at
>>
>> com.google.appengine.tools.development.JettyContainerService.startContainer
>> (JettyContainerService.java:188)
>>        at
>> com.google.appengine.tools.development.AbstractContainerService.startup
>> (AbstractContainerService.java:120)
>>        at
>> com.google.appengine.tools.development.DevAppServerImpl.start
>> (DevAppServerImpl.java:217)
>>        at com.google.appengine.tools.development.DevAppServerMain
>> $StartAction.apply(DevAppServerMain.java:162)
>>        at com.google.appengine.tools.util.Parser$ParseResult.applyArgs
>> (Parser.java:48)
>>        at
>> com.google.appengine.tools.development.DevAppServerMain.
>> (DevAppServerMain.java:113)
>>        at com.google.appengine.tools.development.DevAppServerMain.main
>> (DevAppServerMain.java:89)
>> 26-Jan-2010 19:00:50 com.google.apphosting.utils.jetty.JettyLogger
>> warn
>> WARNING: failed ser...@7eb1cc87
>> java.net.SocketException: Invalid argument
>>        at sun.nio.ch.Net.bind(Native Method)
>>        at sun.nio.ch.ServerSocketChannelImpl.bind
>> (ServerSocketChannelImpl.java:119)
>>        at sun.nio.ch.ServerSocketAdaptor.bind
>> (ServerSocketAdaptor.java:59)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.open
>> (SelectChannelConnector.java:211)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
>> (SelectChannelConnector.java:309)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at org.mortbay.jetty.Server.doStart(Server.java:228)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at
>>
>> com.google.appengine.tools.development.JettyContainerService.startContainer
>> (JettyContainerService.java:188)
>>        at
>> com.google.appengine.tools.development.AbstractContainerService.startup
>> (AbstractContainerService.java:120)
>>        at
>> com.google.appengine.tools.development.DevAppServerImpl.start
>> (DevAppServerImpl.java:217)
>>        at com.google.appengine.tools.development.DevAppServerMain
>> $StartAction.apply(DevAppServerMain.java:162)
>>        at com.google.appengine.tools.util.Parser$ParseResult.applyArgs
>> (Parser.java:48)
>>        at
>> com.google.appengine.tools.development.DevAppServerMain.
>> (DevAppServerMain.java:113)
>>        at com.google.appengine.tools.development.DevAppServerMain.main
>> (DevAppServerMain.java:89)
>> java.net.SocketException: Invalid argument
>>        at sun.nio.ch.Net.bind(Native Method)
>>        at sun.nio.ch.ServerSocketChannelImpl.bind
>> (ServerSocketChannelImpl.java:119)
>>        at sun.nio.ch.ServerSocketAdaptor.bind
>> (ServerSocketAdaptor.java:59)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.open
>> (SelectChannelConnector.java:211)
>>        at org.mortbay.jetty.nio.SelectChannelConnector.doStart
>> (SelectChannelConnector.java:309)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at org.mortbay.jetty.Server.doStart(Server.java:228)
>>        at org.mortbay.component.AbstractLifeCycle.start
>> (AbstractLifeCycle.java:40)
>>        at
>>
>> com.google.appengine.tools.development.JettyContainerService.startContainer
>> (JettyContainerService.java:188)
>>        at
>> com.google.appengine.tools.development.AbstractContainerService.startup
>> (AbstractContainerService.java:120)
>>        at
>> com.google.appengine.tools.development.DevAppServerImpl.start
>> (DevAppSer

Re: [appengine-java] Converting Entity to Object

[Scott Hernandez]

http://code.google.com/p/objectify-appengine

(it seems it got truncated from John's message)

On Tue, Feb 2, 2010 at 10:32 AM, John Patterson  wrote:
> You can check out Twig or Objectify which all aim to do what you are asking
> about.
>
> Twig is higher level - more like an Object database built on top of the
> datastore in which you use the native low-level Queries.  Objectify is more
> low level in that you handle relationships between objects manually with
> Keys but has great docs.  Both make use of generics to make your code more
> maintainable.
>
> http://code.google.com/p/twig-persist/
>
> On 2 Feb 2010, at 18:08, Alexandru Farcas wrote:
>
>> Is there a way of converting dynamically an Entity to a specific
>> Object ?
>> For example:
>> I have some Contact objects and User, Invoice etc, witch are
>> PersistanceCapable.
>> So i can make queries (javax.jdo.Query) that return lists of those
>> kind of objects (Contact, User, Invoice etc) or i can use app engine
>> datastore.Query to get lists of Entity objects.
>> 1. Is there a simple method of converting an Entity object to a
>> Contact for example? but without doing smth like :
>>       map = entitiy.getProperties();
>>       Contact c = new Contact();
>>       c.setProperty1(map.get("property1"));
>>       c.setProperty2()
>>       ... etc
>>
>>     I want to know this because i want to use Query from the
>> datastore package and not javax.jdo and it doesn't seem a good
>> solution to make a method for each kind of entity. (I could use java
>> reflection to create the objects, but i think it is very complicated
>> since i don't know for example the types of fields and it is probably
>> a costly method).
>>
>> 2. Is the Query class form app engine datastore package more powerful
>> (or more suited) than the one from javax.jdo? Witch would you
>> recommend ?
>>
>> --
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>>
>
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Re: [appengine-java] Converting Entity to Object

[John Patterson]

You can check out Twig or Objectify which all aim to do what you are  
asking about.


Twig is higher level - more like an Object database built on top of  
the datastore in which you use the native low-level Queries.   
Objectify is more low level in that you handle relationships between  
objects manually with Keys but has great docs.  Both make use of  
generics to make your code more maintainable.


http://code.google.com/p/twig-persist/

On 2 Feb 2010, at 18:08, Alexandru Farcas wrote:


Is there a way of converting dynamically an Entity to a specific
Object ?
For example:
I have some Contact objects and User, Invoice etc, witch are
PersistanceCapable.
So i can make queries (javax.jdo.Query) that return lists of those
kind of objects (Contact, User, Invoice etc) or i can use app engine
datastore.Query to get lists of Entity objects.
1. Is there a simple method of converting an Entity object to a
Contact for example? but without doing smth like :
   map = entitiy.getProperties();
   Contact c = new Contact();
   c.setProperty1(map.get("property1"));
   c.setProperty2()
   ... etc

 I want to know this because i want to use Query from the
datastore package and not javax.jdo and it doesn't seem a good
solution to make a method for each kind of entity. (I could use java
reflection to create the objects, but i think it is very complicated
since i don't know for example the types of fields and it is probably
a costly method).

2. Is the Query class form app engine datastore package more powerful
(or more suited) than the one from javax.jdo? Witch would you
recommend ?

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Re: [appengine-java] Re: production memcache grabTail namespace isolation broken

[Ikai L (Google)]

That's interesting. Let me follow up with the team to try to understand how
this is supposed to work.

On Tue, Feb 2, 2010 at 12:05 AM, phraktle  wrote:

>
> Plus, it's working okay in the development server :)
>
> V.
>
> On Feb 2, 9:03 am, phraktle  wrote:
> > Hi,
> >
> > In this case grabTail would be quite useless, as one cannot really
> > construct queues with it (ie. it would just force removing items from
> > all namespaces that wouldn't even expire otherwise). The documentation
> > also implies that there's a separate LRU list per namespace, which
> > does make sense, but is not what's happening in production:
> >
> > http://code.google.com/appengine/docs/java/javadoc/com/google/appengi..
> .)
> >
> > "Grabs (atomically get and delete) items off the tail of LRU list.
> > This can be used to implement queue system with high throughput and
> > low latency, but low reliability. Current namespace should be set and
> > not empty for the service. For each namespace memcache maintains a
> > separate LRU list."
> >
> > Regards,
> >   Viktor
> >
> > On Feb 1, 9:22 pm, "Ikai L (Google)"  wrote:
> >
> >
> >
> > > I'll raise the issue with some other members of the team, but it seems
> like
> > > this is working as expected. A memcache namespace is nothing more than
> a
> > > prefix applied to a memcache key. There's no true partitioning
> mechanism
> > > within memcache. grabTail simply returns the item that would be expired
> by
> > > the LRU mechanism if memcache needed more space. There isn't a
> different
> > > "queue" per namespace, only a "queue" for global expirations.
> >
> > > On Mon, Feb 1, 2010 at 4:29 AM, phraktle  wrote:
> > > > Hi,
> >
> > > > On production, grabTail returns objects from other namespaces. This
> is
> > > > a significant problem that
> > > > makes grabTail (thus queue-like usage) unusable.
> >
> > > > I filed this as a bug, with a very simple example here:
> > > >http://code.google.com/p/googleappengine/issues/detail?id=2706
> >
> > > > Can you please look into this? I don't even see a workaround that I
> > > > can implement in the meantime...
> >
> > > > Thanks,
> > > >  Viktor
> >
> > > > --
> > > > You received this message because you are subscribed to the Google
> Groups
> > > > "Google App Engine for Java" group.
> > > > To post to this group, send email to
> > > > google-appengine-j...@googlegroups.com.
> > > > To unsubscribe from this group, send email to
> > > > google-appengine-java+unsubscr...@googlegroups.com unsubscr...@googlegroups.com>
> > > > .
> > > > For more options, visit this group at
> > > >http://groups.google.com/group/google-appengine-java?hl=en.
> >
> > > --
> > > Ikai Lan
> > > Developer Programs Engineer, Google App Enginehttp://
> googleappengine.blogspot.com|http://twitter.com/app_engine
>
> --
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>


-- 
Ikai Lan
Developer Programs Engineer, Google App Engine
http://googleappengine.blogspot.com | http://twitter.com/app_engine

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[appengine-java] Datastore migration

[Moritz]

Hello everyone,

after a couple of versions of my application I found out that I need
to change the datamodel fundamentally in order to achieve better
performance. My approach was as follows:

(Coding)
- Mark all old API as @Deprecated
- Create new classes etc.
- Update views etc.
- Develop a migration servlet which copies data from the old model to
the new model
(Migration)
- Deploy new app
- Call migration servlet URL

All tests on my local development environment were successful. The new
datamodel is less complex than the old one, it contains only
"implicit" relations and stores large data in a separate entity. That
perfectly matches the application's scope, only minor refactorings
were necessary to implement the new datamodel.

However, the migration failed. Of course, I had already so much data
in the system, that the request timed out. Now my datastore is half
old and half new.

Bummer.

Luckily, that application is not really in production, so it is not a
fatal loss.

However, I'm wondering how such migration is usually done.
- How do I backup my datastore?
- How do I run migration "scripts" (in my case =servlet)?

Thank you,
Moritz

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[appengine-java] non-deterministic datastore behaviour while unit testing

[Markus Scheidgen]

Hi,

I use junit to unit test my app according to the "Unit Testing With
Local Service Implementations" tutorial. Once I use owned
relationships within my data-model, the datastore sometimes behaves
unexpected. Objects and links stored in the datastore, sometimes can
not be read from the data store. The data store behaves as if those
objects or links have never been stored. In some runs everything
behaves like it ought to be, in other runs it doesn't. Especially when
I use the eclipse debug mode, the test-cases often have different
outcomes than running them without a debugger.

What troubles me the most, is the non-deterministic scheme. Sometimes
it works, sometimes it doesn't.

So far, I only had this during unit testing. When using the
development server or the cloud, everything worked out as it should.

Does anybody had experienced something similar? Any hind? Maybe there
is some common pit-fall in using the jdo data store or owned
relationships (even though I use it along the documentation and
tutorials).

Thanks,
Markus

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[appengine-java] My application stopped working

[Stéphane Traumat]

Hello... My application as running well since some days : http://www.quatuo.com/
( quatuo-www )

Today, i connect and i see a 500 error message... no Idea why...
nothing in the logs... I tried to empty queues, redeploy and all...
but still nothing is working :(
I need help as peoples just can't use the service anymore.. and i have
no idea why.

Regards

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Re: [appengine-java] access compute and storage clouds with jclouds

[nicolas melendez]

100k lines of code ? consider do some refactor :)

On Tue, Feb 2, 2010 at 2:37 PM, Adrian Cole  wrote:

> jclouds is an open source framework that helps you get started in the
> cloud and reuse your java development skills. Our api allows you to
> freedom to use portable abstractions or cloud-specific features. We
> support many clouds including Amazon, VMWare, Azure, and Rackspace.
>
> After over 7 months and 100k lines of code, jclouds 1.0-beta-3 is out!
>
> This release is focused on choice.  Choice of cloud providers and
> choice in tooling to manage them.
>
> Inside the jclouds distribution, you will find 15 service choices,
> including EC2, Atmos, vCloud, Azure, and Rimu Hosting.  You can choose
> to use these apis directly, or use a multi-cloud abstraction like
> BlobStore [1] or ComputeService [2].
>
> You can also use jclouds via ant, commons vfs, infinispan, crane
> clojure, or dasein cloud apis.
>
> As before, we've been careful to ensure everything works well in or
> outside google appengine.  We even have a new spring demo to show that
> off [3].
> Unlike before, we now have a binary distribution you can download [4].
>
> Please do let us know what you'd like to see from us next.
>
> All the best,
> -Adrian
> founder jclouds
>
> [1] http://code.google.com/p/jclouds/wiki/BlobStore
> [2] http://code.google.com/p/jclouds/wiki/ComputeGuide
> [3] http://java.dzone.com/articles/using-spring%E2%80%99s-java
> [4] http://code.google.com/p/jclouds/downloads/list
>
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>

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Re: [appengine-java] Re: problem with Datastore quotas

[Dombrowski, Todd]

Nevermind -- looks like a wide spread problem, being discussed on the
appengine list already ...

On Tue, Feb 2, 2010 at 9:07 AM, Dombrowski, Todd  wrote:

> Most likely indexes -- "app engine maintains an index for every query the
> app engine will perform" (from Programming Google App Engine)
>
> If you have a variety of queries that use multiple properties and sort
> orders, the datastore will need an index for every unique combination -- and
> this is in addition to the indexes already created on every key and property
> for a "kind". Sort order is significant too -- you may need an index in ASC
> and DESC order for a property.
>
> Another thing to look out for: using more than one multi-valued property in
> an entity. Your index on those properties basically becomes the cross
> product of the values stored, which can make it huge.
>
> If you don't have it, the book "Programming Google App Engine" has the best
> treatment I've seen of the datastore.
>
> Thanks,
> Todd Dombrowski
> pzlbox
>
>
>
>
> On Tue, Feb 2, 2010 at 5:50 AM, Jorge  wrote:
>
>> Hi Dimitar,
>>
>> This is an idea. Take a closer look to your _ah_SESSION kind. It is
>> possible you are storing huge session data and it remains there after
>> the sessions expire. If that is the case, you probably want to clean
>> your expired sessions periodically.
>>
>> Jorge Gonzalez
>>
>>
>> On Feb 1, 1:05 pm, dmakariev  wrote:
>> > Hi again,
>> >
>> > I've read the documentation. and cannot find anything related to my
>> > datastore growth :(,
>> > I'm not using indexes. It is quite simple application, demonstrating
>> > the usage of JSF 2. I'm using session, and I've included the
>> > SessionCleanupServlet in my web.xml. It is started every hour.
>> > So the number of entities in _ah_SESSION is round 40 .
>> >
>> > My other suspect was the log file. I couldn't find any description
>> > about where the log files are stored.
>> > But I've updated the version number of the application.. deleted the
>> > old one with the big log files, and still the total used datastore
>> > quota didn't decrease.
>> >
>> > my current status is 35% of Total Stored Data
>> > and at the same time : Size of all entities 414 KBytes
>> >
>> > I'll be really happy to know where and how to manage properly the
>> > datastore space.
>> >
>> > Best Regards:
>> > Dimitar Makariev
>> >
>> > On Feb 1, 1:38 am, John Patterson  wrote:
>> >
>> > > On the page that shows those details is a link to a doc that explains
>>
>> > > where the extra space is used.  Probably indexes could consume a lot.
>> >
>> > > On 1 Feb 2010, at 16:29, dmakariev wrote:
>> >
>> > > > Hi all,
>> > > > I have the following problem :
>> > > > my quotas show the following :
>> > > > Total Stored Data   26% 0.26 of 1.00 GBytes Okay
>> > > > at the same time
>> > > > Datastore Statistics is showing :
>> > > > Size of all entities:  5 MBytes
>> >
>> > > > Breakdown by Property Type
>> > > > Property Type  Size
>> > > > Blob5 MBytes
>> > > > String  14 KBytes
>> > > > Integer 12 KBytes
>> > > > Date/Time   4 KBytes
>> > > > User51 Bytes
>> > > > NULL24 Bytes
>> > > > Metadata71 KBytes
>> >
>> > > > And I have no idea where is the datastore space disappearing..
>> >
>> > > > my app id is "sandcode"
>> >
>> > > > Does anybody has idea ? I'll appreciate your advices..
>> >
>> > > > Best Regards:
>> > > > Dimitar Makariev
>> >
>> > > > --
>> > > > You received this message because you are subscribed to the Google
>> > > > Groups "Google App Engine for Java" group.
>> > > > To post to this group, send email to
>> google-appengine-java@googlegroups.com
>> > > > .
>> > > > To unsubscribe from this group, send email to
>> google-appengine-java+unsubscr...@googlegroups.com
>> > > > .
>> > > > For more options, visit this group athttp://
>> groups.google.com/group/google-appengine-java?hl=en
>> > > > .
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "Google App Engine for Java" group.
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>> google-appengine-j...@googlegroups.com.
>> To unsubscribe from this group, send email to
>> google-appengine-java+unsubscr...@googlegroups.com
>> .
>> For more options, visit this group at
>> http://groups.google.com/group/google-appengine-java?hl=en.
>>
>>
>

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[appengine-java] Can't compile Guestbook demo modified as in the video

[SD]

Hello,

I tried to modify guestbook java files as in the video tutorial
(http://www.youtube.com/watch?v=P3GT4-m_6RQ), but apparently did
something wrong as can't compile it.
I've added JDK in eclipse preferences (instead of JRE) and seem to
have all required components (I am not a java programmer as you see),
so it could be just a mistake in the code.

Debugging in Eclipse points to this line in GuestbookServlet.java:
GuestBookEntry entry = new GuestBookEntry(poster, content);

It says: "Multiple markers at this line
- Occurence of 'GuestBookEntry
- GuestBookEntry cannot be resolved to a type
- GuestBookEntry cannot be resolved to a type
- Occurence of 'GuestBookEntry'

I also have one warning in GuestbookEntry.java:
@PrimaryKey
  @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
  private Long id;
(the field is never read locally)

Here is a long error message from the Console:
org.apache.jasper.compiler.Compiler generateClass
SEVERE: Javac exception
Compile failed; see the compiler error output for details.
at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:933)
at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:757)
at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:
382)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:472)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
at org.apache.jasper.JspCompilationContext.compile
(JspCompilationContext.java:511)
at org.apache.jasper.servlet.JspServletWrapper.service
(JspServletWrapper.java:295)
at org.apache.jasper.servlet.JspServlet.serviceJspFile
(JspServlet.java:292)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
at com.google.appengine.tools.development.PrivilegedJspServlet.access
$101(PrivilegedJspServlet.java:23)
at com.google.appengine.tools.development.PrivilegedJspServlet$2.run
(PrivilegedJspServlet.java:59)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.PrivilegedJspServlet.service
(PrivilegedJspServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
487)
at org.mortbay.jetty.servlet.ServletHandler.handle
(ServletHandler.java:362)
at org.mortbay.jetty.security.SecurityHandler.handle
(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle
(SessionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle
(ContextHandler.java:712)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
405)
at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle
(DevAppEngineWebAppContext.java:70)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:268)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)
at
com.google.appengine.tools.development.StaticFileUtils.serveWelcomeFileAsForward
(StaticFileUtils.java:80)
at
com.google.appengine.tools.development.LocalResourceFileServlet.maybeServeWelcomeFile
(LocalResourceFileServlet.java:254)
at
com.google.appengine.tools.development.LocalResourceFileServlet.doGet
(LocalResourceFileServlet.java:120)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
487)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1093)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter
(ServeBlobFilter.java:51)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1084)
at
com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter
(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1084)
at com.google.appengine.tools.development.StaticFileFilter.doFilter
(StaticFileFilter.java:121)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1084)
at org.mortbay.jetty.servlet.ServletHandler.handle
(ServletHandler.java:360)
at org.mortbay.jetty.security.SecurityHandler.handle
(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle
(SessionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle
(ContextHandler.java:712)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
405)
at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle
(DevAppEngineWebAppContext.java:70)
at org.mortbay.jetty.handler.HandlerWrapper.handle
(HandlerWrap

Re: [appengine-java] Re: problem with Datastore quotas

[Dombrowski, Todd]

Most likely indexes -- "app engine maintains an index for every query the
app engine will perform" (from Programming Google App Engine)

If you have a variety of queries that use multiple properties and sort
orders, the datastore will need an index for every unique combination -- and
this is in addition to the indexes already created on every key and property
for a "kind". Sort order is significant too -- you may need an index in ASC
and DESC order for a property.

Another thing to look out for: using more than one multi-valued property in
an entity. Your index on those properties basically becomes the cross
product of the values stored, which can make it huge.

If you don't have it, the book "Programming Google App Engine" has the best
treatment I've seen of the datastore.

Thanks,
Todd Dombrowski
pzlbox



On Tue, Feb 2, 2010 at 5:50 AM, Jorge  wrote:

> Hi Dimitar,
>
> This is an idea. Take a closer look to your _ah_SESSION kind. It is
> possible you are storing huge session data and it remains there after
> the sessions expire. If that is the case, you probably want to clean
> your expired sessions periodically.
>
> Jorge Gonzalez
>
>
> On Feb 1, 1:05 pm, dmakariev  wrote:
> > Hi again,
> >
> > I've read the documentation. and cannot find anything related to my
> > datastore growth :(,
> > I'm not using indexes. It is quite simple application, demonstrating
> > the usage of JSF 2. I'm using session, and I've included the
> > SessionCleanupServlet in my web.xml. It is started every hour.
> > So the number of entities in _ah_SESSION is round 40 .
> >
> > My other suspect was the log file. I couldn't find any description
> > about where the log files are stored.
> > But I've updated the version number of the application.. deleted the
> > old one with the big log files, and still the total used datastore
> > quota didn't decrease.
> >
> > my current status is 35% of Total Stored Data
> > and at the same time : Size of all entities 414 KBytes
> >
> > I'll be really happy to know where and how to manage properly the
> > datastore space.
> >
> > Best Regards:
> > Dimitar Makariev
> >
> > On Feb 1, 1:38 am, John Patterson  wrote:
> >
> > > On the page that shows those details is a link to a doc that explains
> > > where the extra space is used.  Probably indexes could consume a lot.
> >
> > > On 1 Feb 2010, at 16:29, dmakariev wrote:
> >
> > > > Hi all,
> > > > I have the following problem :
> > > > my quotas show the following :
> > > > Total Stored Data   26% 0.26 of 1.00 GBytes Okay
> > > > at the same time
> > > > Datastore Statistics is showing :
> > > > Size of all entities:  5 MBytes
> >
> > > > Breakdown by Property Type
> > > > Property Type  Size
> > > > Blob5 MBytes
> > > > String  14 KBytes
> > > > Integer 12 KBytes
> > > > Date/Time   4 KBytes
> > > > User51 Bytes
> > > > NULL24 Bytes
> > > > Metadata71 KBytes
> >
> > > > And I have no idea where is the datastore space disappearing..
> >
> > > > my app id is "sandcode"
> >
> > > > Does anybody has idea ? I'll appreciate your advices..
> >
> > > > Best Regards:
> > > > Dimitar Makariev
> >
> > > > --
> > > > You received this message because you are subscribed to the Google
> > > > Groups "Google App Engine for Java" group.
> > > > To post to this group, send email to
> google-appengine-java@googlegroups.com
> > > > .
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[appengine-java] Need some pointers about XMLHttpRequest and Google user services

[Shai]

Hi,
I need some clarifications about how to use the Google users services
when when working with XMLHttpRequest (javascript).

For the purpose of the discussion I use the code from the Google
sample of user services:
http://code.google.com/appengine/docs/java/gettingstarted/usingusers.html

I need to load an html file that has some elements in it that I fill
from a XMLHttpRequest response (I can't use a server generated page
because I'm doing the call from a Google chrome extension and I need
the chrome api, so the html file must be packed with my extension)

My problem is handling the redirect when user is not logged in... How
would you suggest I mimic the browser behavior for the same
redirect ?
If I point my browser to same URL I will get the user log-in page and
the browser will then display the response properly (after the user
signed in).

I am not even sure what to ask, is there some kind of "good practice"
for doing what I need ? Loading a page with and XMLHttpReqest that
requires a redirect to the Google account login and then loading my
page again this time with the user signed in ?




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[appengine-java] Converting Entity to Object

[Alexandru Farcas]

Is there a way of converting dynamically an Entity to a specific
Object ?
For example:
I have some Contact objects and User, Invoice etc, witch are
PersistanceCapable.
So i can make queries (javax.jdo.Query) that return lists of those
kind of objects (Contact, User, Invoice etc) or i can use app engine
datastore.Query to get lists of Entity objects.
1. Is there a simple method of converting an Entity object to a
Contact for example? but without doing smth like :
map = entitiy.getProperties();
Contact c = new Contact();
c.setProperty1(map.get("property1"));
c.setProperty2()
... etc

  I want to know this because i want to use Query from the
datastore package and not javax.jdo and it doesn't seem a good
solution to make a method for each kind of entity. (I could use java
reflection to create the objects, but i think it is very complicated
since i don't know for example the types of fields and it is probably
a costly method).

2. Is the Query class form app engine datastore package more powerful
(or more suited) than the one from javax.jdo? Witch would you
recommend ?

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[appengine-java] access compute and storage clouds with jclouds

[Adrian Cole]

jclouds is an open source framework that helps you get started in the
cloud and reuse your java development skills. Our api allows you to
freedom to use portable abstractions or cloud-specific features. We
support many clouds including Amazon, VMWare, Azure, and Rackspace.

After over 7 months and 100k lines of code, jclouds 1.0-beta-3 is out!

This release is focused on choice.  Choice of cloud providers and
choice in tooling to manage them.

Inside the jclouds distribution, you will find 15 service choices,
including EC2, Atmos, vCloud, Azure, and Rimu Hosting.  You can choose
to use these apis directly, or use a multi-cloud abstraction like
BlobStore [1] or ComputeService [2].

You can also use jclouds via ant, commons vfs, infinispan, crane
clojure, or dasein cloud apis.

As before, we've been careful to ensure everything works well in or
outside google appengine.  We even have a new spring demo to show that
off [3].
Unlike before, we now have a binary distribution you can download [4].

Please do let us know what you'd like to see from us next.

All the best,
-Adrian
founder jclouds

[1] http://code.google.com/p/jclouds/wiki/BlobStore
[2] http://code.google.com/p/jclouds/wiki/ComputeGuide
[3] http://java.dzone.com/articles/using-spring%E2%80%99s-java
[4] http://code.google.com/p/jclouds/downloads/list

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[appengine-java] Re: AppEngine Java JDO Posting - need help

[niraj]

If the Last URL does not work use this

http://www.elance.com/job?jobid=19035975&rid=1KDB9



On Feb 2, 7:26 am, niraj  wrote:
> If anyone on this group is interested in AppEngine-Java-JDO work and
> make some quick bucks please look at the posting on elance
>
> http://shar.es/aM73b

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[appengine-java] AppEngine Java JDO Posting - need help

[niraj]

If anyone on this group is interested in AppEngine-Java-JDO work and
make some quick bucks please look at the posting on elance

http://shar.es/aM73b

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[appengine-java] Re: problem with Datastore quotas

[Jorge]

Hi Dimitar,

This is an idea. Take a closer look to your _ah_SESSION kind. It is
possible you are storing huge session data and it remains there after
the sessions expire. If that is the case, you probably want to clean
your expired sessions periodically.

Jorge Gonzalez


On Feb 1, 1:05 pm, dmakariev  wrote:
> Hi again,
>
> I've read the documentation. and cannot find anything related to my
> datastore growth :(,
> I'm not using indexes. It is quite simple application, demonstrating
> the usage of JSF 2. I'm using session, and I've included the
> SessionCleanupServlet in my web.xml. It is started every hour.
> So the number of entities in _ah_SESSION is round 40 .
>
> My other suspect was the log file. I couldn't find any description
> about where the log files are stored.
> But I've updated the version number of the application.. deleted the
> old one with the big log files, and still the total used datastore
> quota didn't decrease.
>
> my current status is 35% of Total Stored Data
> and at the same time : Size of all entities 414 KBytes
>
> I'll be really happy to know where and how to manage properly the
> datastore space.
>
> Best Regards:
> Dimitar Makariev
>
> On Feb 1, 1:38 am, John Patterson  wrote:
>
> > On the page that shows those details is a link to a doc that explains  
> > where the extra space is used.  Probably indexes could consume a lot.
>
> > On 1 Feb 2010, at 16:29, dmakariev wrote:
>
> > > Hi all,
> > > I have the following problem :
> > > my quotas show the following :
> > > Total Stored Data           26%     0.26 of 1.00 GBytes     Okay
> > > at the same time
> > > Datastore Statistics is showing :
> > > Size of all entities:  5 MBytes
>
> > > Breakdown by Property Type
> > > Property Type      Size
> > > Blob        5 MBytes
> > > String      14 KBytes
> > > Integer     12 KBytes
> > > Date/Time   4 KBytes
> > > User        51 Bytes
> > > NULL        24 Bytes
> > > Metadata    71 KBytes
>
> > > And I have no idea where is the datastore space disappearing..
>
> > > my app id is "sandcode"
>
> > > Does anybody has idea ? I'll appreciate your advices..
>
> > > Best Regards:
> > > Dimitar Makariev
>
> > > --
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Re: [appengine-java] Re: Merge join on list properties / more efficient on one list or on separate lists

[John Patterson]

I have read somewhere that all properties (lists or otherwise) are  
stored in an Entity including the property name. An Entity is a Bag of  
properties rather than a Set of Lists.  Therefore your two approaches  
would take the same amount of storage for the Entity and your two  
queries would essentially be the exactly same.  Also, every property  
generates one implicit index entry so that should also be the same.  I  
would keep the fields separate as they are logically distinct.


On 2 Feb 2010, at 17:18, Raphael André Bauer wrote:


On Thu, Jan 28, 2010 at 11:14 AM, Max  wrote:

Bump!

In my opinion, the 2nd one performs better but use more storage.
Because the first one fan out (n + m) copies whereas the second one
fans out (n * m) copies.

This is just MY THEORY. Please correct me if I am wrong.


thanks Max :)

does anybody have a pointer to a specification where I could look up
the exact time and space consumption of both querys on GAE?


Thanks,

Raphael


Thanks a lot,

Max

On 1月28日, 上午1時06分, Raphael André Bauer  


wrote:

Hi everybody,

Suppose you have to entities. Entity1 has one list, Entity2 has  
two lists:


Entity1
List tags_and_timestamps

Entity2
List tags
List timestamps

(I hope the peseudocode is ok - the questions is a general datastore
question and not dependent on JPA/JDO or low-level api).

Then I want to merge join my entities based on two properties: a
timestamp and on a tag.

Entity1 is a stupid entity simply storing everyhting in one list.
So I merge join on one list:
tags_and_timestamps == timestamp AND tags_and_timestamps == tag

Entity2 is separates both values, so I merge join on:
timestamps == timestamp AND tags == tag

The question is now: What is more efficient on the GAE datastore?
Separating the values into different lists or storing everything in
one list?

Thanks a lot,

Raphael


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[appengine-java] Persisting during scheduled maintenance periods using JDO

[Ian Marshall]

In the GAE/J documentation under "How-To | Handling Scheduled
Maintenance Periods", it states:

"During this period, all datastore writes and transactions will throw
an exception. Your application can detect these errors and indicate to
the user that the application is in read-only, recommending that they
try again later."

An example is then given to catch the relevant exception during
PersistenceManager#makePersistent(...), but I cannot find an example
for datastore updates of already-existing entities.

Does anyone know at what point an update to a persistent entity (not
using PersistenceManager#makePersistent(...)) will result in the
CapabilityDisabledException exception being thrown? For example, where
in the following code extract could I expect this exception?

// Non-GAE method to return the singleton instance
PersistenceManagerFactory pmf =
DataExchange.getPersistenceManagerFactory();

PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx = pm.currentTransaction();

try
{
  tx.begin();

// Non GAE method to get a detatched instance by its ID
(within the current tx)
Item itemEdit = findItemByID(tx, pidData.loID,
loLoggedOnUserID);

// Non GAE method to amend the itemEdit instance
itemEdit = updateItemWithPageItemData(tx, itemEdit, pidData,
ipmMode);

tx.commit();
}
finally
{
  try
  {
if (tx.isActive())// Because of an exception, say
{
  tx.rollback();
}
  }
  finally
  {
pm.close();
  }
}

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Re: [appengine-java] Re: Merge join on list properties / more efficient on one list or on separate lists

[Raphael André Bauer]

On Thu, Jan 28, 2010 at 11:14 AM, Max  wrote:
> Bump!
>
> In my opinion, the 2nd one performs better but use more storage.
> Because the first one fan out (n + m) copies whereas the second one
> fans out (n * m) copies.
>
> This is just MY THEORY. Please correct me if I am wrong.

thanks Max :)

does anybody have a pointer to a specification where I could look up
the exact time and space consumption of both querys on GAE?


Thanks,

Raphael
>
> Thanks a lot,
>
> Max
>
> On 1月28日, 上午1時06分, Raphael André Bauer 
> wrote:
>> Hi everybody,
>>
>> Suppose you have to entities. Entity1 has one list, Entity2 has two lists:
>>
>> Entity1
>> List tags_and_timestamps
>>
>> Entity2
>> List tags
>> List timestamps
>>
>> (I hope the peseudocode is ok - the questions is a general datastore
>> question and not dependent on JPA/JDO or low-level api).
>>
>> Then I want to merge join my entities based on two properties: a
>> timestamp and on a tag.
>>
>> Entity1 is a stupid entity simply storing everyhting in one list.
>> So I merge join on one list:
>> tags_and_timestamps == timestamp AND tags_and_timestamps == tag
>>
>> Entity2 is separates both values, so I merge join on:
>> timestamps == timestamp AND tags == tag
>>
>> The question is now: What is more efficient on the GAE datastore?
>> Separating the values into different lists or storing everything in
>> one list?
>>
>> Thanks a lot,
>>
>> Raphael
>
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[appengine-java] Re: here is currently a bug preventing owned one-to-many relationships where the parent and the child are the same class, making it difficult to model tree structures.

[Ian Marshall]

Yes, this is datanucleus-appengine issue 80 (Recursive relation does
not work). I have starred this issue, along with 29 others.

I could not wait for the fix, so I have already worked around this
issue by having all my entities of this type:
  ·  having the same entity group parent (of a different class)
  ·  using an ArrayList<[Entity]> of key values to store each entity's
"children"
  ·  using a key value to store each entity's "parent" (null for the
root instance, even though it still has a entity group parent).

This is not ideal for me, but it works well.

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[appengine-java] Re: Unsupported method while parsing expression:

[datanucleus]

>    query.setFilter("aliases == alias");

That is invalid JDOQL syntax; the spec is the spec and JDOQL uses Java
syntax.
If you have a collection field then the filter should be

aliases.contains(:alias)

The poster put the colon in front of a field name (wrong), and
declared a parameter as a variable (wrong).

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Re: [appengine-java] JDO - GWT - JUNIT testing examples

[Andreas Blomqvist]

Htmlunit doesnt work on GAE due to restrictions. Getting this error:

java.lang.NoClassDefFoundError: java.net.URLStreamHandler is a restricted
class. Please see the Google  App Engine developer's guide for more details.

If anyone has any insights on how to resolve this please let me know.
Thinking of the same approach as this blogs:
http://esxx.blogspot.com/2009/06/using-apaches-httpclient-on-google-app.html

/A


On 27 January 2010 22:24, Ikai L (Google)  wrote:

> I'm no expert on how to unit test GWT, but in terms of testing the server,
> for a unit test it probably is a better idea to simply test the servlet.
> I've heard HtmlUnit is pretty good for this. Here's a guide for setting up
> JUnit to work with the datastore:
>
> http://code.google.com/appengine/docs/java/howto/unittesting.html
>
>
> On Tue, Jan 26, 2010 at 7:19 AM, aswath satrasala <
> aswath.satras...@gmail.com> wrote:
>
>> Hi,
>> I am using GWT and JDO to write a simple create and list Employee
>> application.  I got this working using TransferObjects .
>> How to test the GWT asysnc calls with local datastore using Junit.
>>
>> -Aswath
>>
>> --
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>>
>
>
>
> --
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> Developer Programs Engineer, Google App Engine
> http://googleappengine.blogspot.com | http://twitter.com/app_engine
>
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[appengine-java] Re: production memcache grabTail namespace isolation broken

[phraktle]

Plus, it's working okay in the development server :)

V.

On Feb 2, 9:03 am, phraktle  wrote:
> Hi,
>
> In this case grabTail would be quite useless, as one cannot really
> construct queues with it (ie. it would just force removing items from
> all namespaces that wouldn't even expire otherwise). The documentation
> also implies that there's a separate LRU list per namespace, which
> does make sense, but is not what's happening in production:
>
> http://code.google.com/appengine/docs/java/javadoc/com/google/appengi...)
>
> "Grabs (atomically get and delete) items off the tail of LRU list.
> This can be used to implement queue system with high throughput and
> low latency, but low reliability. Current namespace should be set and
> not empty for the service. For each namespace memcache maintains a
> separate LRU list."
>
> Regards,
>   Viktor
>
> On Feb 1, 9:22 pm, "Ikai L (Google)"  wrote:
>
>
>
> > I'll raise the issue with some other members of the team, but it seems like
> > this is working as expected. A memcache namespace is nothing more than a
> > prefix applied to a memcache key. There's no true partitioning mechanism
> > within memcache. grabTail simply returns the item that would be expired by
> > the LRU mechanism if memcache needed more space. There isn't a different
> > "queue" per namespace, only a "queue" for global expirations.
>
> > On Mon, Feb 1, 2010 at 4:29 AM, phraktle  wrote:
> > > Hi,
>
> > > On production, grabTail returns objects from other namespaces. This is
> > > a significant problem that
> > > makes grabTail (thus queue-like usage) unusable.
>
> > > I filed this as a bug, with a very simple example here:
> > >http://code.google.com/p/googleappengine/issues/detail?id=2706
>
> > > Can you please look into this? I don't even see a workaround that I
> > > can implement in the meantime...
>
> > > Thanks,
> > >  Viktor
>
> > > --
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>
> > --
> > Ikai Lan
> > Developer Programs Engineer, Google App 
> > Enginehttp://googleappengine.blogspot.com|http://twitter.com/app_engine

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[appengine-java] Re: production memcache grabTail namespace isolation broken

[phraktle]

Hi,

In this case grabTail would be quite useless, as one cannot really
construct queues with it (ie. it would just force removing items from
all namespaces that wouldn't even expire otherwise). The documentation
also implies that there's a separate LRU list per namespace, which
does make sense, but is not what's happening in production:

http://code.google.com/appengine/docs/java/javadoc/com/google/appengine/api/memcache/MemcacheService.html#grabTail(int)

"Grabs (atomically get and delete) items off the tail of LRU list.
This can be used to implement queue system with high throughput and
low latency, but low reliability. Current namespace should be set and
not empty for the service. For each namespace memcache maintains a
separate LRU list."



Regards,
  Viktor


On Feb 1, 9:22 pm, "Ikai L (Google)"  wrote:
> I'll raise the issue with some other members of the team, but it seems like
> this is working as expected. A memcache namespace is nothing more than a
> prefix applied to a memcache key. There's no true partitioning mechanism
> within memcache. grabTail simply returns the item that would be expired by
> the LRU mechanism if memcache needed more space. There isn't a different
> "queue" per namespace, only a "queue" for global expirations.
>
>
>
>
>
> On Mon, Feb 1, 2010 at 4:29 AM, phraktle  wrote:
> > Hi,
>
> > On production, grabTail returns objects from other namespaces. This is
> > a significant problem that
> > makes grabTail (thus queue-like usage) unusable.
>
> > I filed this as a bug, with a very simple example here:
> >http://code.google.com/p/googleappengine/issues/detail?id=2706
>
> > Can you please look into this? I don't even see a workaround that I
> > can implement in the meantime...
>
> > Thanks,
> >  Viktor
>
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> --
> Ikai Lan
> Developer Programs Engineer, Google App 
> Enginehttp://googleappengine.blogspot.com|http://twitter.com/app_engine

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