Persist classes with inheritance using Gilead

Question

I'm using Gilead to persist my entities in my GWT project and I've run into an issue. I'd like to create a parent class to hold some properties that are common throughout my entities (id, etc). When persisting I get a null pointer exception.

Parent class:

public abstract class Entity extends LightEntity implements Serializable {
    protected Long id;
    public Entity(){}
}

Child class:

public class Person extends Entity  {
    private String firstName;
    private String lastName;
    public Person(){}
}

Hibernate mapping file:

<hibernate-mapping>
    <class name="com.domain.Entity" abstract="true" >
        <id name="id" type="long">
                <column name="ID"/>
                <generator class="native" />
            </id>
        <union-subclass name="com.domain.Person" table="PERSON">
            <property name="id" type="long" />
            <property name="firstName" type="string">
                <column name="FIRST_NAME" length="45" not-null="true" />
            </property>
            <property name="lastName" type="string">
                <column name="LAST_NAME" length="45" not-null="true" />
            </property>
        </union-subclass>
    </class>
</hibernate-mapping>

Stack trace when persisting:

java.lang.NullPointerException at net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:170) at com.google.gwt.user.server.rpc.RemoteServiceServlet.doPost(RemoteServiceServlet.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:754) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:427) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:315) at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:287) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:218) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593) at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94) at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:222) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:166) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096) at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:288) at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:647) at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:579) at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:831) at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341) at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263) at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214) at com.sun.enterprise.web.portunif.PortUnificationPipeline$PUTask.doTask(PortUnificationPipeline.java:380) at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265) at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)

Answer 1

Are you using Gilead < 1.2.2?

If yes, upgrade Gilead. And then run again and check the new exception message. Most likely just some kind of misconfiguration.

Full explanation:

If you check the source code of PersistentRemoteService.java in version 1.2.1

PersistentRemoteService.java v1.2.1

at line 170 you see the following line

return RPCCopy.getInstance().encodeResponseForFailure(null, ex, rpcRequest.getSerializationPolicy());

This obviously fails with a NullPointerException if rpcRequest is null.

That happens when in line 143

// Decode request
rpcRequest = RPCCopy.getInstance().decodeRequest(payload, this.getClass(), this);

The decodeRequest-Method throws an IncompatibleRemoteServiceException. Which it does in your case.

Starting with version 1.2.2 the line 170 changes to

if (rpcRequest != null)
{
  return RPCCopy.getInstance().encodeResponseForFailure(null, ex, rpcRequest.getSerializationPolicy());
}
else
{
    return RPCCopy.getInstance().encodeResponseForFailure(null, ex);
}

Now you should get the right exception (IncompatibleRemoteServiceException)which points you to the real problem.

You can also check the corresponding commit/fix in SVN

Bad exception fix (issue 2663344)

and the corresponding issue entry in the Bug-Tracker for Gilead

Wrong exception

So this issue is solved in SVN since February 07 2009 or since Gilead version 1.2.2 (March 13 2009)

Answer 2

Not sure if it helps. Just a speculation. Did you try with non-abstract superclass? Sometimes manually nullifying/eagerly loading lazy object references or lists before serializing (and of course outside current transaction scope) just works, and there is no need to Gilead.