Hi,
> I am attempting to load all the persistent class metadata eagerly.
OpenJPA provides several ways to load persistent metadata eagerly. The
suggested approaches assume that META-INF/persistence.xml has listed the
persistent classes.
1. <property name="openjpa.InitializeEagerly" value="true"/> is arguably the
most straightforward approach, notwithstanding some comments on this thread
about this option that had stated otherwise.
2. Create a dummy EntityManager with
EntityManagerFactory.createEntityManager(). Metadata initialization will
kick in that way too.
Kevin Sutter wrote:
>
> Hi Heather,
> Interesting use of the OpenJPA metadata processing. Just from your brief
> description, I would be careful on depending on an implementation versus
> defined interfaces. Even if we could get this initialization done earlier
> for you, unless there was some defined mechanism to force this (ie. the
> openjpa.InitializeEagerly property), I wouldn't count on it. In this
> particular case, the metadata repository is meant for OpenJPA processing.
>
> I know with OpenJPA the lines may not be crystal clear between public
> API's,
> provider SPI's, or internal classes. Of course, since this is an
> open-source project, you are welcome to peruse the complete contents of
> the
> code base and see if a solution is doable or not. I would just be careful
> on being too dependent on a specific implementation.
>
> Kevin
>
> On Fri, May 15, 2009 at 9:30 AM, Heather Sterling <hst...@us.ibm.com>
> wrote:
>
>> Thanks Kevin.
>>
>> Our scenario is that we have added product-specific annotations to the
>> persistent classes. In particular, we have some annotations that we need
>> in
>> our perPersist entity listener to generate unique identifiers before the
>> object is persisted. We're currently initializing all of the metadata at
>> the
>> beginning. We essentially iterate through the persistent classes and
>> create
>> maps that hold this extra information. I guess it's possible for us to
>> lazily load this data in the entity listener if it hasn't been loaded for
>> a
>> particular class. I also looked to see if there was another hook we could
>> potentially use, but didn't see any that seemed to fit the problem.
>>
>>
>> Heather Sterling
>> Systems Management Development
>> Phone: 919-254-7163 T/L: 444-7163
>> Cell: 919-423-3143
>> Email: hst...@us.ibm.com
>>
>>
>> [image: Inactive hide details for Kevin Sutter ---05/12/2009 12:53:30
>> PM---Heather,]
>> Kevin Sutter ---05/12/2009 12:53:30 PM---Heather,
>>
>>
>>
>>
>> *Kevin Sutter <kwsut...@gmail.com>*
>>
>> 05/12/2009 12:48 PM
>> Please respond to users
>>
>>
>>
>> To: users@openjpa.apache.org
>> cc:
>> Subject: Re: correct way to load persistent metadata at startup
>>
>>
>> Heather,
>> Good question... :-) This topic has come up recently due to some
>> potential
>> locking issues (serialized access) when reading the metadata repository
>> in
>> a
>> multi-threaded environment. At this point, there is not a clear cut
>> answer
>> for forcing the initialization of the metadata repository. The code for
>> the
>> new openjpa.InitializeEagerly property was committed to trunk last August
>> (after the 1.2.0 release was created), but we've since determined that it
>> may not be complete for all cases. You are welcome to try it out from
>> either the 1.3.x or trunk branches and see if it helps in your particular
>> situation.
>>
>> Let us know what you find out. Also, can you explain your need for
>> getting
>> this data eagerly vs letting the lazy loading process play out? Thanks!
>>
>> Kevin
>>
>>
>>
>> On Mon, May 11, 2009 at 2:40 PM, Heather Sterling <hst...@us.ibm.com>
>> wrote:
>>
>> >
>> >
>> > I am attempting to load all the persistent class metadata eagerly. I
>> > realize this isn't great performance-wise, but I need to do it for the
>> > time-being. I had wanted to call:
>> >
>> > ClassMetaData[] classMetaDatas =
>> > conf.getMetaDataRepositoryInstance().getMetaDatas();
>> >
>> > but realized the data was loaded lazily when nothing came back. I
>> switched
>> > to using:);
>> >
>> > Collection c =
>> conf.getMetaDataRepositoryInstance().loadPersistentTypes(.
>> > true, null);
>> >
>> > which returned the classes to me, but getMetaDatas() still returned
>> > nothing. Finally, I resorted to iterating through the class names,
>> which
>> > seemed to work.
>> >
>> > Set names = conf.getMetaDataRepositoryInstance
>> > ().getPersistentTypeNames(false, null);
>> > if (names != null) {
>> > for (Iterator it = names.iterator(); it.hasNext();) {
>> > String persistentClassname = (String)it.next();
>> > System.out.println("Pre-loading metadata for: " +
>> > persistentClassname);
>> > try {
>> > ClassMetaData cc =
>> conf.getMetaDataRepositoryInstance
>> > ().getMetaData(Class.forName(persistentClassname), null, true);
>> > } catch (ClassNotFoundException e) {
>> > // TODO Auto-generated catch block
>> > e.printStackTrace();
>> > }
>> >
>> > }
>> > }
>> >
>> > I found a link regarding a potential openjpa property called
>> > openjpa.InitializeEagerly (
>> > https://issues.apache.org/jira/browse/OPENJPA-620) but it was never
>> > checked
>> > into a release.
>> >
>> > Given all these options, what is the correct way to load the metadata
>> on
>> > startup?
>> >
>> >
>> > Heather Sterling
>> > Systems Management Development
>> > Phone: 919-254-7163 T/L: 444-7163
>> > Cell: 919-423-3143
>> > Email: hst...@us.ibm.com
>>
>
>
-----
Pinaki Poddar http://ppoddar.blogspot.com/
http://www.linkedin.com/in/pinakipoddar
OpenJPA PMC Member/Committer
JPA Expert Group Member
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