Problems with Persistence.xml not on class path

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

I am using Hibernate Entity Manager 3.31GA, annotations 3.30GA and core 3.2.

I have an application with a 'plugin' system. The plugins are in JARs in a subdirectory. The main application searches the JARs for classes implementing a particular interface, and loads those using URLClassLoader.
The problem arises when one of these plugins tries to use the Entity Manager. The plugin JAR has a persistence.xml file, but the system class loaders don't seem to 'know' about this JAR because it isn't on the class path.

The usual thing is to get the following:

Code:

INFO  - Hibernate EntityManager 3.3.1.GA
DEBUG - Look up for persistence unit: WhateverPU
INFO  - Could not find any META-INF/persistence.xml file in the classpath
java.util.concurrent.ExecutionException: javax.persistence.PersistenceException: No Persistence provider for EntityManager named WhateverPU
etc...

I also tried using Ejb3Configuration (out of desperation because it's not portable) - but here I suffer from lack of documentation. Can I somehow give a URL to the persistence.xml in the JAR file? If I try to specify everything else programmatically, without referring to the persistence.xml, Hibernate seems to expect .hbm.xml files for classes that are actually annotated:

Code:

                  Ejb3Configuration ejbc = new Ejb3Configuration();
  return ejbc.addClass(Cards.class)
                                 .addClass(Places.class)
                                       .addProperties(map)
                                       .buildEntityManagerFactory();
                 

And this produces:

Code:

INFO  - Reading mappings from resource: com/tvg_tech/holypass/general/Cards.hbm.xml
INFO  - Reading mappings from resource: com/tvg_tech/holypass/general/Cards.hbm.xml
java.util.concurrent.ExecutionException: org.hibernate.MappingNotFoundException: resource: com/xxx/xxx/general/Cards.hbm.xml not found

Many thanks,
Shalom Crown

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

Well I didn't see the Ejb3Configuration method addAnnotatedClass - which solves that problem - but I think there is another similar one. Even though the Entity manager starts OK:

Code:

INFO  - Binding entity from annotated class: com.xxx.xxx.general.Cards
DEBUG - Binding column DTYPE unique false
DEBUG - Import with entity name=Cards
INFO  - Bind entity com.xxx.xxx.general.Cards on table Cards
DEBUG - Processing com.txxx.xxx.general.Cards property annotation
DEBUG - Processing com.xxx.xxx.general.Cards field annotation
DEBUG - Processing annotations of com.xxx.xxx.general.Cards.id
DEBUG - Binding column id unique false
DEBUG - id is an id
DEBUG - building SimpleValue for id
DEBUG - Building property id
DEBUG - Cascading id with null
DEBUG - Bind @Id on id
DEBUG - Processing annotations of com.xxx.xxx.general.Cards.GUID
DEBUG - Binding column GUID unique false
DEBUG - binding property GUID with lazy=false
DEBUG - building SimpleValue for GUID
DEBUG - Building property GUID
DEBUG - Cascading GUID with null

Etc.

Soon, it runs into problems - again, to do with the class loader not being able to find the class in the plugin JAR:

Code:

WARN  - Unable to apply constraints on DDL for com.xxx.xxx.general.Cards
java.lang.ClassNotFoundException: com.xxx.xxx.general.Cards
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:247)
        at org.hibernate.annotations.common.util.ReflectHelper.classForName(ReflectHelper.java:78)
        at org.hibernate.annotations.common.reflection.java.JavaReflectionManager.classForName(JavaReflectionManager.java:74)
        at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:158)
etc..

I would still prefer to use the standard JPA API, rather than Hibernate's specific things.

There is a persistence.xml tag called jpa-file - which allows you to specify a URL to the persistence.xml. If I could add this information programmatically, it would save a lot of problems.
- Shalom Crown

emmanuel · **Posted:** Tue Jul 17, 2007 3:11 pm

If you set the ThreadLocal classloader that sees the persistence.xml and the entity classes before calling Persistence.create... you should be fine I guess.

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

I don't understand what you mean by 'ThreadLocal classloader'. Is there some ThreadLocal variable that the Persistence class uses?

I also tried adding the plugin JAR to and Ejb3Configuration using

Code:

.addResource(jarPath, this.getClass().getClassLoader())

Where 'jarPath' is the absolute path of the plugin JAR and 'this' is the plugin class - but this failed with "resource ..... .jar not found".

In the end I will have to ask the plugin developer to add his JAR file to the class path (say - on the command line that starts the application). This is ugly, but not unreasonable.

- Shalom Crown

emmanuel · **Posted:** Wed Jul 18, 2007 1:29 pm

Code:

Thread.currentThread().setContextClassLoader();

shalom · **Joined:** Mon May 28, 2007 4:20 am **Posts:** 6

Well - that certainly works!

Many thanks!

- Shalom Crown