title: JPA and GWT failing
body: <p>I'm trying to use JPA with GWT.</p>
  
  <p>My serviceImpl calls</p>
  
  <pre><code>UserDAO.exists(user);
  </code></pre>
  
  <p>When I run a test case, which calls the same method, with the same parameters, it runs ok. When I do the RPC call, if fails horribly (error at the end).</p>
  
  <p>When I rename persistence.xml to someothername.xml, I get the SAME error, so I'm inclined to think that GWT (in development mode BTW), is NOT reading my persistence.xml.</p>
  
  <p>The error:</p>
  
  <pre><code>Starting Jetty on port 8888
     [WARN] Exception while dispatching incoming RPC call
  com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract hobarrera.client.dto.main.UserRegDTO hobarrera.client.services.AuthService.selfRegisterUser(java.lang.String,java.lang.String,java.lang.String,java.lang.String) throws hobarrera.client.exceptions.MyCustomizedException' threw an unexpected exception: java.lang.ExceptionInInitializerError
   at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:378)
   at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:581)
   at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:188)
   at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:224)
   at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
   at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
   at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
   at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
   at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
   at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
   at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
   at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
   at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
   at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
   at org.mortbay.jetty.Server.handle(Server.java:324)
   at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
   at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843)
   at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647)
   at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
   at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
   at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
   at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)
  Caused by: java.lang.ExceptionInInitializerError
   at hobarrera.server.DAO.EntityManagerFactory.createEntityManager(EntityManagerFactory.java:13)
   at hobarrera.server.DAO.UsuarioDAO.userNameExists(UsuarioDAO.java:52)
   at hobarrera.server.services.AuthServiceImpl.selfRegisterUser(AuthServiceImpl.java:60)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:616)
   at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:562)
   ... 22 more
  Caused by: javax.persistence.PersistenceException: No resource files named META-INF/services/javax.persistence.spi.PersistenceProvider were found. Please make sure that the persistence provider jar file is in your classpath.
   at javax.persistence.Persistence.findAllProviders(Persistence.java:167)
   at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:103)
   at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83)
   at hobarrera.server.DAO.EntityManagerFactory$RealEntityManagerFactoryContainer.&lt;clinit&gt;(EntityManagerFactory.java:9)
   ... 30 more
  [ERROR] 500 - POST /desarrollonew/greet (0:0:0:0:0:0:0:1) 57 bytes
     Request headers
        Host: localhost:8888
        User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100216 Fedora/3.5.8-1.fc12 Firefox/3.5.8
        Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
        Accept-Language: en-us,en;q=0.5
        Accept-Encoding: gzip,deflate
        Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
        Keep-Alive: 300
        Connection: keep-alive
        Referer: http://localhost:8888/desarrollonew/hosted.html?desarrollonew
        Cache-Control: no-cache
        X-GWT-Permutation: HostedMode
        X-GWT-Module-Base: http://localhost:8888/desarrollonew/
        Content-Type: text/x-gwt-rpc; charset=utf-8
        Content-Length: 187
        Pragma: no-cache
     Response headers
        Content-Type: text/plain
  </code></pre>
  
  <p><strong>[edit]</strong><br>
  It seems GWT has it's own persistence.xml file somewhere (for internal use I guess).
  That's why renaming my persistence.xml to somethingelse.xml still gave the same error: The persistence.xml file which was being read was GWT's all the time.</p>
  
  <p>So now my question is: How do I override it, force the usage of another one, or live without it?</p>