CODEWITHSUNDEEP
google-app-enginejpaandroid-studiopersistenceentitymanager
Stephan Celis
Stephan Celis

Reputation: 2612

No persistence provider for my EntityManager in appengine backend

I'm using Android Studio and I've created an app engine backend with the tools provided by Android Studio. I'm trying to use JPA/Persistence in my backend module for my android application. When I try my API to store some data I get the Exception

java.lang.ExceptionInInitializerError
    at be.stece.esocomm.backendApp.EsoCommEndpoint.getEntityManager(EsoCommEndpoint.java:73)
....
Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named esoCommBackendPersistence
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:69)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)

So the problem lies somewhere with my setup or project structure. Since it can't find my persistence provider. But I can't figure out where the problem lies.

First of all in my build.gradle file of this backend module I have the dependecies:

  compile 'javax.servlet:servlet-api:2.5'
  compile group: 'org.hibernate.javax.persistence', name: 'hibernate-jpa-2.0-api', version: '1.0.0.Final'
  compile 'org.hibernate:hibernate-entitymanager:4.1.7.Final'

Then in MyModule/src/META_INF/persistence.xml I have declared everything:

<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
  <persistence-unit name="esoCommBackendPersistence">
    <provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider>
    <properties>
      <property name="datanucleus.NontransactionalRead" value="true" />
      <property name="datanucleus.NontransactionalWrite" value="true" />
      <property name="datanucleus.ConnectionURL" value="appengine" />
      <property name="datanucleus.appengine.datastoreEnableXGTransactions"
        value="true" />
      <property name="datanucleus.appengine.autoCreateDatastoreTxns"
        value="true" />
    </properties>
    <class>be.stece.esocomm.backendApp.NewsBean</class>
  </persistence-unit>
</persistence>

I'm not 100% sure if the persistence.xml is in the right directory. I've tried several options, like moving the META_INF folder to the /src/main folder instead of just /src. But no difference.

To create my EntityManager I use the correct Persistence name

public class MyEntityManagerFactory {

    private static final String PERSISTENCE_NAME = "esoCommBackendPersistence";

    private static final EntityManagerFactory emfInstance =
            Persistence.createEntityManagerFactory(PERSISTENCE_NAME);

    private MyEntityManagerFactory() {}

    public static EntityManagerFactory get() {
        return emfInstance;
    }

}

 private static EntityManager getEntityManager() {
        return MyEntityManagerFactory.get().createEntityManager(); => The error is triggered on this line
    }

Upvotes: 1

Views: 916

Answers (1)

Stephan Celis
Stephan Celis

Reputation: 2612

Ok, so I got it to work.

I removed all hibernate and use the appengine persistence as per suggestion of Neil Stockton.

dependencies {
  appengineSdk 'com.google.appengine:appengine-java-sdk:1.8.9'
  compile 'com.google.appengine:appengine-endpoints:1.8.9'
  compile 'com.google.appengine:appengine-endpoints-deps:1.8.9'
  compile 'javax.servlet:servlet-api:2.5'

    // Persistence
    compile 'org.ow2.asm:asm:4.0'
    compile 'org.datanucleus:datanucleus-api-jpa:3.1.3'
    compile 'org.datanucleus:datanucleus-api-jdo:3.1.3'
    compile 'com.google.appengine.orm:datanucleus-appengine:2.1.2'
    compile 'org.datanucleus:datanucleus-core:3.1.3'
    compile 'org.apache.geronimo.specs:geronimo-jpa_2.0_spec:1.0'
    compile 'javax.jdo:jdo-api:3.0.1'
    compile 'javax.transaction:jta:1.1'
}

Also now I followed the following guides to create the endpoints: https://developers.google.com/appengine/docs/java/datastore/entities#Java_Kinds_and_identifiers

Upvotes: 1

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