Question

Started a new project from scratch, converted to JPA, my persistence provider is EclipseLink, added the necessary libraries (eclipselink.jar, eclipselink.jar, javax.persistence, mysql-connector-java-5.1). Tested the connection, ping ok. Then created a new package New > JPA > Entities from Tables > Selected all Entities and Key generator > Identity.

GestorIpca.java

            GestorIpcaService.util.getInstance().getLista(new AsyncCallback<ArrayList<Docente>>() {

                @Override
                public void onFailure(Throwable caught) {
                    Window.alert("Erro na Ligacao efectuada");
                    caught.getStackTrace();
                }

                @Override
                public void onSuccess(ArrayList<Docente> result) {
                    Window.alert("Ligacao efectuada com sucesso:" + result.size());
                }
            });    

GestorIpcaService

@RemoteServiceRelativePath("greet")
public interface GestorIpcaService extends RemoteService {
    String greetServer(String name) throws IllegalArgumentException;

    public static class util{
        public static GestorIpcaServiceAsync instance;
        public static GestorIpcaServiceAsync getInstance(){
            if(instance == null){
                instance = GWT.create(GestorIpcaService.class);
            }
        return instance;
        }
    }
    public ArrayList<Docente> getLista() throws IllegalArgumentException;
}    

GestorIpcaServiceAsync

public interface GestorIpcaServiceAsync {
        void greetServer(String input, AsyncCallback<String> callback)
                throws IllegalArgumentException;

        void getLista(AsyncCallback<ArrayList<Docente>> callback);
    }

GestorIpcaServiceImpl

@SuppressWarnings("serial")
public class GestorIpcaServiceImpl extends RemoteServiceServlet implements
        GestorIpcaService {

    public ArrayList<Docente> getLista() throws IllegalArgumentException  {
        //Criamos um EntityManager
        EntityManager em = JpaUtil.getEntityManagerFactory().createEntityManager();
        //Criamos a consulta
        String consulta = "SELECT r from Docente r";
        //Executamos a consulta
        Query q = em.createQuery(consulta);
        ArrayList<Docente> lista = new ArrayList<Docente>(q.getResultList());
        return lista;
    }
/*  public static void main(String args[]){
        GestorIpcaServiceImpl serviceImpl = new GestorIpcaServiceImpl();
        for (Docente docente : serviceImpl.getLista()){
            System.out.println("nome: " + docente.getNome());
        }
    }
    */   

In this file i tried to run as > Java Application and in Console showed me 2 records.
Package com.GestorIpca.factory

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public class JpaUtil {
    private static final EntityManagerFactory emf;
    //Método estático
    static{
        //BLoco try
        try
        {
            //Criação de EntityManagerFactory
            emf = Persistence.createEntityManagerFactory("GestorIpca");
        }catch (Throwable e){
            //Controlar as excepções
            System.err.println("A criação de SessionFactory falhou" + e);
            e.printStackTrace();
            throw new ExceptionInInitializerError(e);
        }
    }

    public static EntityManagerFactory getEntityManagerFactory(){
        return emf;
    }
}    

My persistence.xml was created automatically. Placed inside META-INF

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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_2_0.xsd">
    <persistence-unit name="GestorIpca">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>

    <class>com.GestorIpca.shared.Ano</class>
    <class>com.GestorIpca.shared.Categoria</class>
    <class>com.GestorIpca.shared.Curso</class>
    <class>com.GestorIpca.shared.Disciplina</class>
    <class>com.GestorIpca.shared.Disponibilidade</class>
    <class>com.GestorIpca.shared.Docente</class>
    <class>com.GestorIpca.shared.Sala</class>
    <class>com.GestorIpca.shared.Semestre</class>
    <class>com.GestorIpca.shared.TipoCurso</class>
    <class>com.GestorIpca.shared.Turma</class>
    <class>com.GestorIpca.shared.User</class>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/timetable"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="k771u3"/>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
        </properties>
    </persistence-unit>
</persistence>

Last step > Run as > Web Application
Error > Could not connect to database and print a stack trace in Eclipse Console

[EL Info]: 2011-05-09 10:03:08.78--ServerSession(8068087)--EclipseLink, version: Eclipse Persistence Services - 2.2.0.v20110202-r8913
[EL Info]: 2011-05-09 10:03:09.297--ServerSession(8068087)--file:/C:/Users/Martinho/WorkSpace/GestorIpca/war/WEB-INF/classes/_GestorIpca login successful
Starting Jetty on port 8888
   [WARN] Exception while dispatching incoming RPC call
com.google.gwt.user.client.rpc.SerializationException: java.lang.reflect.InvocationTargetException
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeWithCustomSerializer(ServerSerializationStreamWriter.java:764)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:727)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:616)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:152)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:534)
    at com.google.gwt.user.server.rpc.RPC.encodeResponse(RPC.java:616)
    at com.google.gwt.user.server.rpc.RPC.encodeResponseForSuccess(RPC.java:474)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:571)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:324)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
    at org.mortbay.jetty.HttpConnection$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$PoolThread.run(QueuedThreadPool.java:488)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeWithCustomSerializer(ServerSerializationStreamWriter.java:746)
    ... 30 more
Caused by: com.google.gwt.user.client.rpc.SerializationException: Type 'org.eclipse.persistence.indirection.IndirectSet' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized.: instance = {IndirectSet: not instantiated}
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:614)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:152)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:534)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeClass(ServerSerializationStreamWriter.java:704)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:734)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:616)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:152)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:534)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeClass(ServerSerializationStreamWriter.java:704)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:734)
    at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:616)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
    at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.serialize(Collection_CustomFieldSerializerBase.java:45)
    at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serialize(ArrayList_CustomFieldSerializer.java:38)
    ... 35 more
[ERROR] 500 - POST /gestoripca/greet (127.0.0.1) 57 bytes
   Request headers
      Host: 127.0.0.1:8888
      Connection: keep-alive
      Referer: http://127.0.0.1:8888/GestorIpca.html?gwt.codesvr=127.0.0.1:9997
      Content-Length: 132
      Origin: http://127.0.0.1:8888
      X-GWT-Module-Base: http://127.0.0.1:8888/gestoripca/
      X-GWT-Permutation: HostedMode
      User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.30 Safari/534.30
      Content-Type: text/x-gwt-rpc; charset=UTF-8
      Accept: */*
      Accept-Encoding: gzip,deflate,sdch
      Accept-Language: pt-PT,pt;q=0.8,en-US;q=0.6,en;q=0.4
      Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
   Response headers
      Content-Type: text/plain    

Note: I changed in package com.GestorIpca.shared all my classes generated from tables

public class Ano implements Serializable 

to

public class Ano implements IsSerializable    

changed also my GestorIpca.gwt.xml and added this lines in end

<extend-configuration-property name="rpc.blacklist" value="com.google.gwt.user.client.ui.*Collection"/>
<extend-configuration-property name="rpc.blacklist" value="-.*List"/>
<extend-configuration-property name="rpc.blacklist" value="-.*Map"/>
<extend-configuration-property name="rpc.blacklist" value="-.*Collection"/>
<extend-configuration-property name="rpc.blacklist" value="+java.util.HashMap"/>
<extend-configuration-property name="rpc.blacklist" value="+java.util.LinkedHashMap"/>
<extend-configuration-property name="rpc.blacklist" value="+java.util.ArrayList"/>

What am i missing?

Answer 1

I depends on how your entities were defined. Maybe there are connections that GWT RPC doesn´t like. in this case i´d suggest create DTO´s or implement RequestFactory