[appengine-java] Re: Coding with Adobe Software
Yes, the w3schools material is good. The mozilla foundation also had a great set of learning materials at http://developer.mozilla.org Click on the learning tab in the upper right. Ed On May 25, 4:00 am, Drew Spencer slugmand...@gmail.com wrote: Sorry dude, I kinda naively assumed you would already have some experience in HTML/CSS. As the two above have said, these are the foundations of all web pages. I highly recommend the tutorials on w3schools.com for both of them. They give a great introduction to becoming a web designer: -http://www.w3schools.com/html/default.aspfirst of all, and then -http://www.w3schools.com/css/default.asp They have a great feature that lets you try things as you go along, but notepad is the way to go also. Try making your own basic web page - practice adn experimentation are the only way you really get things to stick in your head. One last link for you:http://www.w3.org/Style/Examples/011/firstcss Have fun! Drew -- 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 at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: Coding with Adobe Software
If you are brand-new to coding, I would not use GWT. I would start with HTML/CSS/Javascript. Many folks start their coding careers there (and many many stay there because they love it). You can get started quickly and the learning curve is not so steep. The learning curve on GWT or even Adobe Flash is very steep at the start. If you are doing a news app, html/css/javascript is probably very appropriate. Note that Javascript and GWT are designed for creating browser delivered UI's, but you can package them up using various technologies to create an application suitable for the app store and android market. I use Flash Builder and the Adobe Flex Framework for most of my client UI work and I love it. I decided to use it about 2 years ago, before GWT was really solid and HTML5 was viable (perhaps it's still not quite viable yet). The tooling is very good and the Flex framework is really outstanding. The Flex framework includes an xml based declarative UI system (mxml) which is really nice for building quick apps. You can graduate to ActionScript3 to do more significant logic. You can package your app for a browser or for iOS or Android devices (and Blackberry Playbook tablet). So, this would be a pretty good choice for your client UI as well. GWT is a truly great set of tooling and it gets better and better with each release. If I were to choose UI tooling for myself today, I would choose GWT because it provides great tooling and path to all the devices I want to target now and in the future. However, I have been doing software engineering for 25 years and I know Java well, so the learning curve is not so bad for me. I would not recommend GWT to someone just learning how to code. On the server side, GAE is a good choice - you don't have to worry about hardware and scaling. However, I would probably choose Python because the learning curve is less steep than Java. (PS: I use Java GAE it is is very good, my recommendation is based on your experience level, not the quality of Java GAE). There are lots of entry level resources for the Python language and the server side framework makes coding many scenarios easier than Java. On the server side, you might also look at CouchDB. This is a distributed database that is accessed via RESTful api's and extended using Javascript. This is a really, really fine solution that makes it easy to create a server that is primarily about saving and retrieving data. You can set this up on your own machine to see how it works. Some folks are combining this with another javascript server technology, called node.js, to create a complete server solution that is programmed in Javascript. You can probably find hosted versions of this combination, so you won't have to setup servers. So, more to your question, How do I code the application so that it functions with the interface?. I create what are referred to as Rich Client Applications (RIA). The client is basically a full application (not a set of pages, like a traditional website), that asks the server for data and then uses it to drive the client UI. When the client wants to save data, it sends it to the server and the server stores it in a database. In my case, the server is pretty simple (as servers go), in that is simply saves data that the client gives to it and gives it back when the client asks for it. I 'expose' the server as a set of RESTful api's that return the data as XML or JSON (note that CouchDB does this as well). I like this architecture because it clearly separates the client and server. By creating a RESTful server api that uses the HTTP standard, I can use ANY client technology to talk to it (javascript, GWT, Flex or ObjectiveC are all doable) Moreover, I can use any server technology to implement the RESTful server api. Basically, I give myself much more flexibility because the client and server technologies are decoupled, so as the world changes, I can change with it. Also, this lets me integrate with 3rd parties much more easily. I hope this helps. Good luck. Coding is the second most fun thing in the world. On May 19, 10:39 pm, Daniel Nieblas pearlharborpreva...@gmail.com wrote: Hi my name is Daniel, I'm new to coding, so everything literally feels like a foreign language at this point, but I decided to start learning because I'm interested in developing a news app for smartphones and tablets. Anyway i'm using the Java version of the GAE SDK and was wondering how exactly does coding incorporate commercial-based software. Im saving up to buy Adobe InDesign CS5.5 so that I can create the user interface for the app, but I'm not sure how exactly that works itself out in relation to coding the app itself. How do I code the application so that it functions with the interface? thanks for helping out:) -- 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
[appengine-java] NoSuchMethodError totalMemory()
My app started throwing exceptions right after the latest maintenance; apparently Runtime.getRuntime().totalMemory() is now actually removed from the server runtime? Couldn't you just return zero? java.lang.NoSuchMethodError: com.google.apphosting.runtime.security.shared.intercept.java.lang.Runtime_.totalMemory(Ljava/lang/Runtime;)J at com.conceptualcalculations.util.MemoryUtils.formatMemoryLog(MemoryUtils.java:23) -- 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 at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: JPA/JDO vs low level API
I've been using Java AppEngine since it became available. I chose JDO for portability and so I could get started very quickly. I can say that JDO offers very little real portability for significant apps because of the very different semantics of the underlying datastore. If I were developing for an SQL datastore, my datamodel would be pretty different. For instance, it is easy in most SQL datastores to use one or more fields as a unique, mutable secondary key (like an email address or Social Security Number). In the appengine datastore, if you have the datastore generate unique primary keys, but you want to enforce a unique mutable secondary key, you need to use a separate entity to serve as the secondary key mutex. This is a fine solution if you are using the low level API, because you can have your data access layer create and check this mutex so this does not bubble up to your application code. However, with JDO, you have to create another pojo and manage it so it can serve as the mutex. Ick. When I chose JDO, no wrapper for the low level existed and documentation of the low level was not great. JDO was well documented so I could get going fast. However, there are now several good alternative frameworks for using the low level datastore. If I were to start today, I would choose one of them and avoid JDO. Now that I know what I know, I will probably write my own low level wrapper so I have more flexibility and control. On Apr 2, 8:46 am, Jeff Schnitzer j...@infohazard.org wrote: An incomplete list of things that are difficult or impossible with JDO/JPA, but easy with Objectify/LowLevelAPI: * Partial indexes * Running multiple concurrent transactions, or (more likely) a transaction + a nontransaction. Because of GAE's transaction model, this is actually necessary quite often. * Migrating your schema. JDO/JPA is particularly brittle, you can't even add primitive fields to a class. * Serializing your entities. With JDO you must detach them explicitly, with JPA (as implemented by DataNucleus) you simply can't. In practice, the biggest difference after abandoning JDO/JPA is that you will stop screaming loudly at your computer, annoying your coworkers. Jeff (copied from the response to the same question on the objectify mailing list) On Fri, Apr 1, 2011 at 4:50 AM, SkYlEsS shou...@gmail.com wrote: I have a question : What are the differences between JPA/JDO and low level API (and Objectify) in practice ? I read everywhere the low level API provides more flexibility, but there are never samples code or evidences to demonstrate it. So I'm wondering in which cases exactly, the low level API is useful ? Thanks in advance -- 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. 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 at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Datastore not responding intermittently
We are testing a update to our app on a couple of qa instances (applications, not just JVMs) of AppEngine. Both are getting DeadlineExceededException pretty often. However, we have only a single user hitting the database and it has little data in it - basically, there is no contention for the database, but sometimes it simply does not respond. Below is an example log. You can see that we use JDO to emit a query for a single entity. However, the datastore never responds. We have the same exact code running on two different AppEngine applications. One of them has instant-on enabled (so it has 3 instances running all the time) and the other does not (so it needs to spin up an instance relatively regularly). We are using JDO and Restlet, but not Spring or Grooving or other packages that take a very long time to initialize (initializing a new instance takes our app about 7 seconds). The very similar code on our live application seems to be fine - we are not seeing the same thing. This makes me worry about deploying to live. Is anyone else seeing this kind of behavior with the datastore? Caused by: com.google.apphosting.api.DeadlineExceededException: This request (d5cf2cc1a60c6af7) started at 2011/03/17 22:49:48.468 UTC and was still executing at 2011/03/17 22:50:17.887 UTC. at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Object.java:502) at com.google.apphosting.runtime.AsyncFuture.get(AsyncFuture.java:54) at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:67) at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:67) at com.google.appengine.api.datastore.FutureHelper.getInternal(FutureHelper.java:71) at com.google.appengine.api.datastore.FutureHelper.quietGet(FutureHelper.java:32) at com.google.appengine.api.datastore.QueryResultsSourceImpl.loadMoreEntities(QueryResultsSourceImpl.java:69) at com.google.appengine.api.datastore.QueryResultsSourceImpl.loadMoreEntities(QueryResultsSourceImpl.java:56) at com.google.appengine.api.datastore.QueryResultIteratorImpl.ensureLoaded(QueryResultIteratorImpl.java:156) at com.google.appengine.api.datastore.QueryResultIteratorImpl.hasNext(QueryResultIteratorImpl.java:65) at org.datanucleus.store.appengine.query.RuntimeExceptionWrappingIterator.hasNext(RuntimeExceptionWrappingIterator.java:44) at org.datanucleus.store.appengine.query.LazyResult.resolveAll(LazyResult.java:115) at org.datanucleus.store.appengine.query.LazyResult.size(LazyResult.java:110) at org.datanucleus.store.appengine.query.StreamingQueryResult.size(StreamingQueryResult.java:124) at org.datanucleus.store.query.Query.executeQuery(Query.java:1508) at org.datanucleus.store.query.Query.executeWithArray(Query.java:1371) at org.datanucleus.jdo.JDOQuery.execute(JDOQuery.java:266) at com.conceptualcalculations.model.Group.GroupMembershipDAO.testSecondaryKey(GroupMembershipDAO.java:185) at com.conceptualcalculations.model.Group.GroupMembershipDAO.testSecondaryKey(GroupMembershipDAO.java:1) at com.conceptualcalculations.persistence.JDOTemplate.innerGetBySecondaryKey(JDOTemplate.java:403) -- 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 at http://groups.google.com/group/google-appengine-java?hl=en.
Re: [appengine-java] how to keep fields unique
It turns out the technique I described in my previous post has two issues. 1. Because only one transaction can be running at a time within a process, and the entity used as the mutex really cannot be in the same entity group as the primary entity, you can get into a situation where the mutex entity is orphaned if one transaction succeeds and the following transaction fails. The orphaned mutex entity then prevents anyone for using it's version of the unique fields. 2. This solution, when used with JDO or JPA, is very verbose and obfuscates the primary intent of the code. Also, you would never to do this with an SQL datastore, so it limits the portability of the code, which is why one would choose JDO/JPA in the first place. Really, we want the uniqueness annotations to be implemented. There is an issue in the bugbase for this, issue 178. Folks have been talking about this for a long time. Please star this issue if it is important to you. http://code.google.com/p/googleappengine/issues/detail?id=178 -- 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 at http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Can I enqueue a task from within another Task handler?
My code attempts to enqueue a new task within a transaction that happens inside a task handler. Basically, I'm trying to enforce strict serial handling by the tasks, so I have my task, as the last thing it does, enqueue another task to the same url (but with a different name, because I let appengine generate a random name). When I first enqueue the task, it is from within a Post that is generated from a client application. This first task execution works correctly (it processes a bunch of work successfully), but then an exception is thrown when it tries to enqueue another task to continue the work. Am I simply doing something that is not allowed? I've looked through the docs, but I don't see anything conclusive. Thanks for your help. -- 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.
[appengine-java] Ancestor queries on explicitly created entity groups in JDO?
In my application I'm using JDO. In some cases, I have un-owned
relationships where I explicitly created my own entity group because I
need to be able to do transactions with a group of records. For
instance;
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = true)
public class Customer
{
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long customerId = null;
...
}
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = true)
public class User
{
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key userId = null;
@Persistent(defaultFetchGroup=true)
private Long customerId = null; // foreign-key for Customer
...
}
When I persist a User, I set the parent part of the userId key, then
let JDO fill in the id portion when I call save(). This all works
well. However, sometimes I want to query a set of User's by the
Customer's id. As you can see above, I've duplicated the customerId
in the User record for this purpose. This works fine, but it takes an
extra field and creates an extra index. What I'd really like to do is
to query the User key's parent part so I can save an index, which
could add up over time. I already have records in a production
database that have the above structure, so anything I do needs to be
backward compatible. Everything I see in the docs assumes that you
are using JDO to maintain owned relationships, but I'm not doing
that. I've tried using the 'parent-pk' field Datanucleus extension in
a query where I create a full Customer Key from the customerId field,
but I get an exception. I believe this is because this 'virtual'
field is created by JDO only for owned relationships (but that is just
a guess). Is there an explicit way within JDO to do an ancestor query
using the parent key if you are using unowned relationships?
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[appengine-java] Turning on GWT in the project causes class not found excepction in my appengine code.
I have an Java App Engine project using SDK 1.3.5 and the latest Restlet GAE 2.0rc4 to implement some restful services. Everything worked well (this has been in product for 6 months) until I added GWT to the project. As soon as I check GWT on in the control panel (without even adding a module) my services start to fail in the development server with the following class not found exception: Couldn't write the XML representation: Provider org.apache.xalan.processor.TransformerFactoryImpl not found Any clues why simply turning GWT on would cause this? Any solutions that you know of? Thanks much. -- 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.
