Error when implementing JPA domain model in separate JAR module

Question

Hi,
I'm using JPA/TopLink Essentials to implement my domain model and services. From an architectural viewpoint I want to implement this as seperate Java project, while my View/Controller is implemented in another Java project. This last project has a dependency on the Model project. Deployment on an OC4J 10.1.3 is ok, but when I use a JSP, I get the following error. (Note that directly implementing my JPA classes in the View/Controller project does not give any errors.)
Thanx, Ronald
java.lang.NullPointerException     at oracle.toplink.essentials.ejb.cmp3.persistence.ArchiveFactoryImpl.createArchive(ArchiveFactoryImpl.java:64)     at oracle.toplink.essentials.ejb.cmp3.persistence.PersistenceUnitProcessor.findPersistenceArchives(PersistenceUnitProcessor.java:227)     at oracle.toplink.essentials.ejb.cmp3.persistence.PersistenceUnitProcessor.findPersistenceArchives(PersistenceUnitProcessor.java:210)     at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initialize(JavaSECMPInitializer.java:239)     at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initializeFromMain(JavaSECMPInitializer.java:278)     at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.getJavaSECMPInitializer(JavaSECMPInitializer.java:81)     at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:119)     at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83)     at com.trfsol.model.JPAResourceBean.getEMF(JPAResourceBean.java:23)     at com.trfsol.model.Service.getEmp(Service.java:28)     at com.trfsol.JPAServlet.doGet(JPAServlet.java:24)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:743)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:719)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:376)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.HttpRequestHandler.doProcessRequest(HttpRequestHandler.java:870)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:451)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.HttpRequestHandler.serveOneRequest(HttpRequestHandler.java:218)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.HttpRequestHandler.run(HttpRequestHandler.java:119)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)     at oracle.oc4j.network.ServerSocketReadHandler$SafeRunnable.run(ServerSocketReadHandler.java:260)     at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) ].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:303)     at java.lang.Thread.run(Thread.java:595)

Answer 1

Servlet class:
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          Collection<Emp> emps = new Service().getEmp();
          for (Emp emp : emps) {
               System.out.println("Emp " + emp.getEname());
In which the Service class comes from the Model project.
Service class:
public EntityManagerFactory getEMF () {
if (emf == null) {
emf = Persistence.createEntityManagerFactory("default", new java.util.HashMap());
return emf;
public Collection<Emp> getEmp(){
EntityManagerFactory emf = getE
EntityManager em = emf.createEntityManager();
try{
Collection<Emp> result = em.createNamedQuery("findAllEmps").getResultList();
return result;
finally{
em.close();
Persistence.xml (in the META-INF dir of the Model project)
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence persistence_1_0.xsd" version="1.0">
<persistence-unit name="default" transaction-type="RESOURCE_LOCAL">
<provider>
oracle.toplink.essentials.PersistenceProvider
</provider>
<class>com.trfsol.Dept</class>
<class>com.trfsol.Emp</class>
<properties>
<property name="toplink.logging.level" value="FINE"/>
<property name="toplink.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
<property name="toplink.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:ORCL"/>
<property name="toplink.jdbc.password" value="tiger"/>
<property name="toplink.jdbc.user" value="scott"/>
</properties>
</persistence-unit>
</persistence>
Regards, Ronald