EntityManager is always null on REST project (netbeans) running on weblogic 12c

Question

I've been working on a REST project on Netbeans 8.2 (compiled using Java 1.7). I'm deploying my web project on a Weblogic Server 12.1.2 and using JPA (w/ Eclipselink) as the persistence engine referencing a JTA datasource that is configured on server.

The problem I have is common from what I investigated in google; however, I was not able to find any solution on the Web that helps me with the issue.

Basically, this is how my persistence.xml file is defined:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" 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 http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="gchPermissionPU" transaction-type="JTA">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <jta-data-source>jdbc.vz.customer.ds</jta-data-source>
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
      <property name="eclipselink.target-server" value="WebLogic"/>
      <property name="javax.persistence.query.timeout" value="660000"/>
      <property name="eclipselink.logging.level" value="ALL"/>
      <property name="eclipselink.persistence-context.flush-mode" value="COMMIT"/>
      <property name="eclipselink.cache.shared.default" value="false"/>
    </properties>
  </persistence-unit>
</persistence>

This is how I use the EntityManager on a class:

@PersistenceContext(unitName = "gchPermissionPU")
protected EntityManager entityManager;

I get the NullPointerException whenever this line is called (the only one in which I reference entityManager by now):

Query permissionsQuery = entityManager.createNativeQuery(nativeSqlQuery.toString());

I believe the NullPointer comes up because the entityManager variable is null.

Here's the basic data source configuration on my weblogic:

I wonder if I need some kind of additional configuration in the weblogic side or any missing piece of code.

Thanks in advance for your time and help. Any clue/feedback is appreciated.

score 3 · Answer 1 · edited May 23 '17 at 10:30

I managed to solve my problem by manually creating EntityManagerFactory and EntityManager, from this answer:

PersistenceContext EntityManager injection NullPointerException

Seems like without EJB references, you need to force the creation of your persistence components. So my team came up with the following solution:

//1. Define the components required for persistence:

@PersistenceUnit(unitName = "gchPermissionPU")
private EntityManagerFactory entityManagerFactory;
private EntityManager entityManager;

//2. Just a method that will create entity manager factory if it is "null"

public final EntityManager getEntityManager() {
    if (entityManagerFactory == null) {
        entityManagerFactory = Persistence.createEntityManagerFactory("gchPermissionPU");
    }
    if (entityManager == null) {
        entityManager = entityManagerFactory.createEntityManager();
    }

    return entityManager;
}

However, I wonder to know if this is the best solution for a Web application that will be used by > 1000 users. I can't believe that a Web application should rely on EJB for injection (maybe because it is Weblogic) but I remember I implemented a similar application on Tomcat some time ago and didn't need to make this "workaround".

If somebody has additional comments or feedback, please let me know.

Thanks.

EntityManager is always null on REST project (netbeans) running on weblogic 12c

1 Answers1