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NPE in remote session [message #803104]

Mon, 20 February 2012 23:31

Dragomir Zoranovic

Messages: 7
Registered: February 2012

Junior Member

Hello,

I am using 2.3.2 version of eclipselink. I´ve got NPE for merging object with remote sessions. Here is a stacktrace:

java.lang.NullPointerException
at org.eclipse.persistence.internal.queries.ContainerPolicy.createWrappedObjectFromExistingWrappedObject(ContainerPolicy.java:697)
at org.eclipse.persistence.mappings.CollectionMapping.mergeIntoObject(CollectionMapping.java:1491)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.mergeIntoObject(ObjectBuilder.java:3466)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.mergeIntoObject(ObjectBuilder.java:3430)
at org.eclipse.persistence.internal.sessions.MergeManager.mergeChangesForRefreshingRemoteObject(MergeManager.java:467)
at org.eclipse.persistence.internal.sessions.MergeManager.mergeChanges(MergeManager.java:361)
at org.eclipse.persistence.sessions.remote.RemoteSession.getObjectCorrespondingTo(RemoteSession.java:230)
at org.eclipse.persistence.queries.ReadObjectQuery.extractRemoteResult(ReadObjectQuery.java:606)
at org.eclipse.persistence.queries.DatabaseQuery.remoteExecute(DatabaseQuery.java:1788)
at org.eclipse.persistence.queries.ReadObjectQuery.remoteExecute(ReadObjectQuery.java:890)
at org.eclipse.persistence.queries.DatabaseQuery.remoteExecute(DatabaseQuery.java:1797)
at org.eclipse.persistence.queries.ReadQuery.remoteExecute(ReadQuery.java:360)
at org.eclipse.persistence.sessions.remote.RemoteSession.executeQuery(RemoteSession.java:129)
at org.eclipse.persistence.internal.sessions.AbstractSession.refreshAndLockObject(AbstractSession.java:3540)
at org.eclipse.persistence.internal.sessions.AbstractSession.refreshObject(AbstractSession.java:3551)
.....

NPE is thrown in the following line:

return referenceDescriptor.getObjectBuilder().wrapObject(mergeManager.getTargetVersionOfSourceObject(unwrapIteratorResult(wrappedObject), referenceDescriptor, targetSession), mergeManager.getSession());

Reference descriptor is attribute of the foreign reference mapping. This attribute is properly initialized on the server side but has NULL value on the client side because is declared as TRANSIENT.

Does anybody have any suggestions?

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Re: NPE in remote session [message #804385 is a reply to message #803104]

Wed, 22 February 2012 15:13

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

It is most likely a bug in RemoteSession. Please log a bug with all of the detailed information to recreate the error.

Does it only occur with refresh?

What purpose are you using RemoteSession for? It is not commonly used in EclipseLink.

James : Wiki : Book : Blog : Twitter

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Re: NPE in remote session [message #804454 is a reply to message #803104]

Wed, 22 February 2012 16:40

Dragomir Zoranovic

Messages: 7
Registered: February 2012

Junior Member

Hi again,

We started using a toplink 13 years ago. Our application is complex and big RMI based three layer application. At that time we have started using remote sessions on our client side. We had to create a lot of patches around toplink, to not use lazy loading and many others nice features. Our idea is to replace old toplink with eclipselink. Apart from remote sessions, application is working pretty fine with eclipselink. Now I am going to apply same patch to eclipselink as we did for toplink and go further with testing. For every problem that I am going to find out, I will create a new post.

I have created simple test project to reproduce same NPE exception as well. Here is a code:

public class MyProject extends Project {
public void init() {
setName("MyProject");
applyLogin();
addDescriptor(buildUserDescriptor());
addDescriptor(buildAddressDescriptor());
}
private ClassDescriptor buildAddressDescriptor() {
RelationalDescriptor addressDescriptor = new RelationalDescriptor();
addressDescriptor.setTableName("ADDRESS");
addressDescriptor.addPrimaryKeyFieldName("ADDRESS.ID");
addressDescriptor.setSequenceNumberName("ADDRESS_SEQ");
addressDescriptor.setSequenceNumberFieldName("ID");
addressDescriptor.setAlias("Address");
addressDescriptor.setJavaClass(Address.class);
DirectToFieldMapping streetMapping = new DirectToFieldMapping();
streetMapping.setAttributeName("street");
streetMapping.setFieldName("ADDRESS.STREET");
addressDescriptor.addMapping(streetMapping);
DirectToFieldMapping idMapping = new DirectToFieldMapping();
idMapping.setAttributeName("id");
idMapping.setFieldName("ID");
addressDescriptor.addMapping(idMapping);
OneToOneMapping userMapping = new OneToOneMapping();
userMapping.setReferenceClass(User.class);
userMapping.setForeignKeyFieldName("USER_ID");
userMapping.setAttributeName("user");
userMapping.setUsesIndirection(false);
addressDescriptor.addMapping(userMapping);
return addressDescriptor;
}
private ClassDescriptor buildUserDescriptor() {
RelationalDescriptor userDescriptor = new RelationalDescriptor();
userDescriptor.setTableName("USER");
userDescriptor.addPrimaryKeyFieldName("USER.ID");
userDescriptor.setSequenceNumberFieldName("ID");
userDescriptor.setSequenceNumberName("USER_SEQ");
userDescriptor.setAlias("User");
userDescriptor.setJavaClass(User.class);
DirectToFieldMapping nameMapping = new DirectToFieldMapping();
nameMapping.setAttributeName("name");
nameMapping.setFieldName("USER.NAME");
userDescriptor.addMapping(nameMapping);
DirectToFieldMapping idMapping = new DirectToFieldMapping();
idMapping.setAttributeName("id");
idMapping.setFieldName("ID");
userDescriptor.addMapping(idMapping);
OneToManyMapping addressesMapping = new OneToManyMapping();
addressesMapping.setAttributeName("addresses");
addressesMapping.setReferenceClass(Address.class);
addressesMapping.setTargetForeignKeyFieldName("USER_ID");
addressesMapping.setUsesIndirection(false);
userDescriptor.addMapping(addressesMapping);
return userDescriptor;
}
public void applyLogin() {
DatabaseLogin login = new DatabaseLogin();
login.usePlatform(new MySQLPlatform());
login.setDriverClassName("com.mysql.jdbc.Driver");
login.setConnectionString("jdbc:mysql://localhost:3306/MyDB");
login.setUserName("user");
login.setPassword("password");
setDatasourceLogin(login);
}
}

public class MyClient {
private static RMIConnection rmiConnection = null;
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("my/client/rmi-client-context.xml");
RMISessionManager rmiSessionManager = (RMISessionManager) ctx.getBean("rmiSessionManager");
try {
rmiConnection = new RMIConnection(rmiSessionManager.getRMIRemoteSessionController());
} catch (RemoteException e) {
e.printStackTrace();
}
testRemoteSessionRefresh();
}
private static void testRemoteSessionRefresh() {
Expression expression = new ExpressionBuilder(User.class).get("name").equal("loder");
Session session = rmiConnection.createRemoteSession();
Vector<User> users = session.readAllObjects(User.class, expression);
User loder = users.get(0);
loder = (User) session.refreshObject(loder);
}
}

Executing client gives NPE with following stracktrace:
Exception in thread "main" java.lang.NullPointerException
at org.eclipse.persistence.internal.queries.ContainerPolicy.createWrappedObjectFromExistingWrappedObject(ContainerPolicy.java:697)
at org.eclipse.persistence.mappings.CollectionMapping.mergeIntoObject(CollectionMapping.java:1491)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.mergeIntoObject(ObjectBuilder.java:3466)
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.mergeIntoObject(ObjectBuilder.java:3430)
at org.eclipse.persistence.internal.sessions.MergeManager.mergeChangesForRefreshingRemoteObject(MergeManager.java:466)
at org.eclipse.persistence.internal.sessions.MergeManager.mergeChanges(MergeManager.java:361)
at org.eclipse.persistence.sessions.remote.RemoteSession.getObjectCorrespondingTo(RemoteSession.java:230)
at org.eclipse.persistence.queries.ReadObjectQuery.extractRemoteResult(ReadObjectQuery.java:606)
at org.eclipse.persistence.queries.DatabaseQuery.remoteExecute(DatabaseQuery.java:1788)
at org.eclipse.persistence.queries.ReadObjectQuery.remoteExecute(ReadObjectQuery.java:890)
at org.eclipse.persistence.queries.DatabaseQuery.remoteExecute(DatabaseQuery.java:1797)
at org.eclipse.persistence.queries.ReadQuery.remoteExecute(ReadQuery.java:360)
at org.eclipse.persistence.sessions.remote.RemoteSession.executeQuery(RemoteSession.java:129)
at org.eclipse.persistence.internal.sessions.AbstractSession.refreshAndLockObject(AbstractSession.java:3540)
at org.eclipse.persistence.internal.sessions.AbstractSession.refreshObject(AbstractSession.java:3551)
at my.client.MyClient.testRemoteSessionRefresh(MyClient.java:55)
at my.client.MyClient.main(MyClient.java:46)

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