Cannot use JPA in Glassfish v4

Question

On Glassfish v4, in this ultra-simple application, I am getting the error: javax.persistence.PersistenceException: No Persistence provider for EntityManager named local when I access the URL: localhost:8080/demo/main

I thought Glassfish v4 is supposed to come with a built-in provider.

The following is the layout in the war file:

$ jar tvf /usr/local/glassfish4/glassfish/domains/domain1/autodeploy/demo.war
    39 Sun Aug 04 17:12:40 HST 2013 META-INF/MANIFEST.MF
     0 Mon Aug 05 16:32:16 HST 2013 META-INF/
   217 Mon Aug 05 16:18:22 HST 2013 META-INF/persistence.xml
     0 Sun Aug 04 17:12:36 HST 2013 WEB-INF/
     0 Mon Aug 05 14:30:06 HST 2013 WEB-INF/classes/
     0 Mon Aug 05 14:45:26 HST 2013 WEB-INF/classes/com/
     0 Mon Aug 05 14:45:26 HST 2013 WEB-INF/classes/com/example/
     0 Mon Aug 05 16:23:28 HST 2013 WEB-INF/classes/com/example/demo/
   236 Mon Aug 05 16:24:26 HST 2013 WEB-INF/classes/com/example/demo/Foo.java
   400 Mon Aug 05 16:25:34 HST 2013 WEB-INF/classes/com/example/demo/Main.java
   168 Mon Aug 05 16:21:04 HST 2013 WEB-INF/classes/com/example/demo/RestApp.java
   564 Mon Aug 05 16:28:10 HST 2013 WEB-INF/classes/com/example/demo/Foo.class
  1006 Mon Aug 05 16:28:10 HST 2013 WEB-INF/classes/com/example/demo/Main.class
   381 Mon Aug 05 16:28:10 HST 2013 WEB-INF/classes/com/example/demo/RestApp.class
   217 Mon Aug 05 16:18:22 HST 2013 WEB-INF/classes/persistence.xml
   284 Sun Aug 04 17:12:40 HST 2013 WEB-INF/glassfish-web.xml
     0 Sun Aug 04 17:12:36 HST 2013 WEB-INF/lib/

Update: persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence">
    <persistence-unit name="local">
        <jta-data-source>jdbc/local</jta-data-source>
    </persistence-unit>
</persistence>

Main.java tries to create and persist an object:

package com.example.demo;

import javax.persistence.Persistence;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

@Path("main")
public class Main {
  @GET
  @Produces("application/json")
  public String main () {
    Foo foo = new Foo();
    foo.setN(7);
    Persistence.createEntityManagerFactory("local").createEntityManager().persist(foo);
    return "main";
  }
}

Foo.java is a trivial entity:

package com.example.demo;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Foo {

  private int n;

  @Id
  public int getN () {
    return n;
  }

  public void setN (int n) {
    this.n = n;
  }

}

RestApp.java is trivial, and it successfully triggers JAX-RS:

package com.example.demo;

import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

@ApplicationPath("/")
public class RestApp extends Application {
}

In Glassfish control panel there is a JDBC Connection Pool called local that successfully pings to a local MySQL 5.6.13 installation. There is a JDBC resource called jdbc/local with Pool Name: local.

How to go about fixing this? Thanks!

Edited: Added persistence.xml above

Answer 1

You have two persistence.xml both at incorrect location :

META-INF/persistence.xml
WEB-INF/classes/persistence.xml

The correct location relative to your war package root is

WEB-INF/classes/META-INF/persistence.xml

Avoid the ambiguity, do not place more than 1 persistence.xml.

Also if you use maven you have to put persistence.xml on src/main/resources to have it assembled at the correct location on the war