Persistence.xml under classes/META-INF makes other jar references to miss

Question

Hi,
When I am adding persistence.xml to classes/META-INF folder where classes folder got other packages under it, classes in such packages are not getting reference to respective jar files in lib folder. So, deployment of the web project in OAS (Oracle application server) 10g fails mentioning NoClassDef found for classes from library jars referred. If I remove persistence.xml from here, the war file is getting deployed. Deployment fails even when the persistence.xml is available anywhere in classpath (like WEB-INF).
What is the reason & how to correct it?Any alternative approach like manifest or use some settings in OAS?

Answer 1

Hi,
To be accessible to the EJB JAR, WAR, or EAR file, a class or a JAR file must be on the deployment classpath. You can achieve this in one of the following ways:
Put the JAR file in the manifest classpath of the EJB JAR or WAR file. Do this by adding a classpath entry to the META-INF/MANIFEST.MF file in the JAR or WAR file. You may specify one or more directories or JAR files, separating them by spaces. The following example shows how the manifest file classpath entry adds the employee/emp-classes.jar file and the employee/classes directory to the classpath of the JAR file that contains the manifest file:
Class-Path: employee/emp-classes.jar employee/classes
Place the JAR file in the library directory of the EAR filethis will make this JAR file available on the application classpath and accessible by all of the modules deployed within the EAR file. By default, this would be the lib directory of the EAR file, although you may configure it to be any directory in the EAR file using the library-directory element in the application.xml deployment descriptor. The following example shows the application.xml file:
<application ...>
<library-directory>myDir/jars</library-directory>
</application>
Java EE allows for persistence support in a variety of packaging configurations. You can deploy your application to the following module types:
EJB modules: you can package your entities in an EJB JAR. When defining a persistence unit in an EJB JAR, the persistence.xml file is not optionalyou must create and place it in the META-INF directory of the JAR alongside the deployment descriptor, if it exists.
Web modules: you can use WAR file to package your entities. In this case, place the persistence.xml file in the WEB-INF/classes/META-INF directory. Since the WEB-INF/classes directory is automatically on the classpath of the WAR, specify the mapping file relative to that directory.
Persistence archives: a persistence archive is a JAR that contains a persistence.xml file in its META-INF directory and the managed classes for the persistence unit defined by the persistence.xml file. Use a persistence archive if you want to allow multiple components in different Java EE modules to share or access a persistence unit. The following example shows how to package entities in a persistence archive:
emp.ear
emp-persitence.jar
META-INF/persistence.xml
META-INF/orm.xml
examples/model/Employee.class
examples/model/Phone.class
examples/model/Address.class
examples/model/Department.class
examples/model/Project.class
Once you created a persistence archive, you can place it in either the root or the application library directory of the EAR. Alternatively, you can place the persistence archive in the WEB-INF/lib directory of a WAR. This will make the persistence unit accessible only to the classes inside the WAR, but it enables the decoupling of the definition of the persistence unit from the web archive itself.
Regards,
Vinay