Allows for on-the-fly persistence units merge without using hardcoded jar urls [SPR-7055]

[spring-projects-issues]

Stéphane Nicoll opened SPR-7055 and commented

Since 3.0.1, DefaultPersistenceUnitManager does not return a MutablePersistenceUnitInfo but the standard PersistenceUnitInfo.

We have an extension of this class that allows to re conciliate multiple persistence.xml in a single one on the fly. Here's the idea. Assume that we have defined an empty persistence unit called "pu" and that is used by our entity manager. Our extensions of the PersistenceUnitManager scans all persistence.xml and if it matches a certain condition (here if the unit name starts with 'pu') then it is re conciliated with our bootstrap persistence unit.

To do so, we use the getPersistenceUnitInfo(String name) of the class. Up to 3.0, it was returning MutablePersistenceUnitInfo. Is there any way to have a protected method that returns the mutable class?

Btw, this is similar to what is described in #7287 except that JPA does not allow two different persistence.xml with the same persistence unit name (Weblogic namely checks that when deploying an app).

What do you think of our approach? I think I can workaround by casting but then:

1. My code is no longer working with Spring 2.5.7
2. Casting isn't ideal

Thanks

---

Affects: 3.0.1

Referenced from: commits 11bb726, 4ee6735

[spring-projects-issues]

Stéphane Nicoll commented

Actually, I take it back. Only the casting isn't ideal. That works fine with 2.5, 3.0 and 3.0.1.

I am interested by your feedback on the approach though!

[spring-projects-issues]

Stéphane Nicoll commented

Take it back again. It's not binary backward compatible. This diff is the culprit
https://fisheye.springsource.org/browse/spring-framework/trunk/org.springframework.orm/src/main/java/org/springframework/orm/jpa/persistenceunit/DefaultPersistenceUnitManager.java?r2=2801&r1=124

Depending on which version of Spring is used to compile this lead to the error. when the code is built against 3.0.1+ it works fine with that version (but breaks with 2.5.x) and the other way around

Caused by: java.lang.NoSuchMethodError: com.bsb.sf.persistence.support.MultiConfigAwarePersistenceUnitManager.getPersistenceUnitInfo(Ljava/lang/String;)Ljavax/persistence/spi/PersistenceUnitInfo;
        at com.bsb.sf.persistence.support.MultiConfigAwarePersistenceUnitManager.doGetPersistenceUnitInfo(MultiConfigAwarePersistenceUnitManager.java:162)

Is there any to get around this?

[spring-projects-issues]

Stéphane Nicoll commented

Here's the hackish workaround

/**
  * Retrieves the persistence unit info with the specified name.
  * <p/>
  * Very hackish implementation due to a non binary backward compatible
  * change between spring 3.0.0 and spring 3.0.1 (see SPR-7055).
  *
  * @param persistenceUnitName the name of the persistence unit
  * @return the persistence unit or <tt>null</tt> if none is found
  * @throws IllegalStateException if the persistence unit could not be retrieved
  */
 private MutablePersistenceUnitInfo doGetPersistenceUnitInfo(String persistenceUnitName) {
     final Method m = ReflectionUtils.findMethod(DefaultPersistenceUnitManager.class,
             "getPersistenceUnitInfo", new Class[]{String.class});
     if (m == null) {
         throw new IllegalStateException("Could not invoke getPersistenceUnitInfo");
     } else {
         try {
             final Object value = m.invoke(this, persistenceUnitName);
             if (value instanceof MutablePersistenceUnitInfo) {
                 return (MutablePersistenceUnitInfo) value;
             } else {
                 throw new IllegalStateException("Could not retrieve MutablePersistenceUnitInfo from [" + value + "]");
             }
         } catch (Exception e) {
             throw new IllegalStateException("Could not invoke getPersistenceUnitInfo", e);
         }
     }
 }

[spring-projects-issues]

Juergen Hoeller commented

As of Spring 3.0.3, DefaultPersistenceUnitManager's getPersistenceUnitInfo method has a 2.5 compatible signature again. We simply extract the MutablePersistenceUnitInfo target from a PersistenceUnitInfo proxy now (which we're dynamically creating in the case of JPA 2.0, since Spring 3.0.1, in order to remain fully compatible with both JPA 1.0 and JPA 2.0). This allows us to consistently return a MutablePersistenceUnitInfo object from that getPersistenceUnitInfo method again.

This will be available in tonight's 3.0.3 snapshot. Feel free to give it an early try...

Juergen

[spring-projects-issues]

Peter Rademaker commented

We've encountered the same problem as Stephane, therefore we gave 3.0.3.BUILD-SNAPSHOT a try.

However, it does not seem to work the same way as it used to.
When we run the code we get the following NPE:
{{
Caused by: java.lang.NullPointerException
at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.getPersistenceUnitInfo(DefaultPersistenceUnitManager.java:341)
at com.acme.entity.MergingPersistenceUnitManager.postProcessPersistenceUnitInfo(MergingPersistenceUnitManager.java:43)
at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.preparePersistenceUnitInfos(DefaultPersistenceUnitManager.java:290)
at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.afterPropertiesSet(DefaultPersistenceUnitManager.java:261)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1469)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1409)
... 60 more
}}

This is how our postProcessPersistenceUnitInfo (which was working with 3.0.0.RELEASE) looks like:

 
@Override
public final void postProcessPersistenceUnitInfo(
		MutablePersistenceUnitInfo newPU) {
	super.postProcessPersistenceUnitInfo(newPU);
	final URL persistenceUnitRootUrl = newPU.getPersistenceUnitRootUrl();
	LOG.debug("Post processing persistence unit info: "
			+ persistenceUnitRootUrl);
	final String persistenceUnitName = newPU.getPersistenceUnitName();
	LOG.debug("Encountered persistenceUnitName " + persistenceUnitName);
	MutablePersistenceUnitInfo oldPU = getPersistenceUnitInfo(persistenceUnitName);
	if (oldPU != null) {
		LOG.debug("Found new PU with name '" + persistenceUnitName
				+ "'. Merging with already processed PU with same name.");
		mergeJarFileURLs(newPU, oldPU);
		mergeManagedClassNames(newPU, oldPU);
		mergeMappingFileNames(newPU, oldPU);
		mergeProperties(newPU, oldPU);
	}
	LOG.info(String.format(
			"Persistence unit %s now contains the following "
					+ "entities: [%s]", persistenceUnitName, StringUtils
					.join(newPU.getManagedClassNames().toArray(), ", ")));
}

[spring-projects-issues]

Juergen Hoeller commented

Good catch! We accidentally broke the case where getPersistenceUnitInfo would return null... Fixed for tonight's 3.0.3 snapshot.

Juergen

[spring-projects-issues]

Stéphane Nicoll commented

Hi Juergen,

This is working fine with 3.0.3. Thanks a lot for the support

[spring-projects-issues]

Stéphane Nicoll commented

We also described our solution over here:
http://www.dzone.com/links/r/configuring_modular_jpa_applications_with_spring.html