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3 Replies Latest reply on Jun 19, 2012 8:38 AM by jaikiran

Losing objects during serialization...

kdolan1 Jun 18, 2012 5:26 PM

I am having an issue calling an EJB method from the web-tier...it's losing some of my objects. First, I'll say that I got around this by adding <in-vm-remote-interface-invocation pass-by-value="false"/> to my standalone.xml file. However, I'm hoping someone may read this and have an a-ha moment that I am just not seeing why it doesn't work w/ pass-by-value=true (default).

I'm upgrading from JBoss 4.0.1sp1 to 7.1.1. My EJB defaults to a remote EJB because I'm not doing anything special to make it "local" (e.g., no annotations, no <local> deployment descriptor elements). In JBoss 4 I'm guessing it was smart enough to detect all calls were local and just passed by reference w/o complaint. W/ JBoss 7 this is not so - I can tell because I had to make a bunch of classes Serializable.

To my issue...

I have an object I'll call MyObj. It has many data members, some primitive and others w/ other data members, etc. Somewhere in the mix are 2 variables of type DocumentImpl and DeferredDocumentImpl (both in org.apache.xerces.dom package). I should be using the classes that ship w/ JBoss 7 (org.apache.xerces module). The apache documentation says that these 2 classes are Serializable. The class that directly contains these classes and all ancestors up to MyObj are Serializable and nothing is marked transient. So I cannot figure out why when I make my call to my EJB, in the web-tier I have actual object instances assigned to my variables and once in my EJB they are null.

I ran my debugger and put a breakpoint once in my EJB. The call stack is below and I've marked w/ asterisks exactly where my objects are lost. Next, I turned TRACE debugging on for org.jboss.as.ejb3 and org.jboss.as.ejb to see if there was some valuable information I was missing only logging WARN and ERROR. Sorry, not much. I then looked at the code for LocalEjbReceiver.processInvocation() and found where it calls clone() for parameters.

1. object should not be null

2. DocumentImpl/DeferredDocumentImpl are not primitives

3. allowPassByReference is not true (at the time)

4. cloner.clone() is not appearing to throw an exception

So at this point, I am puzzled why object instances are lost and am really just curious to know why. All thoughts are welcome. But again, with that said I've changed my configuration to be pass by reference so I'm able to move on.

MyEjbImpl.myMethod(MyObj) line: 812

NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method]

NativeMethodAccessorImpl.invoke(Object, Object[]) line: 39

DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25

Method.invoke(Object, Object...) line: 597

ManagedReferenceMethodInterceptorFactory$ManagedReferenceMethodInterceptor.processInvocation(InterceptorContext) line: 72

InterceptorContext.proceed() line: 288

WeavedInterceptor.processInvocation(InterceptorContext) line: 53

UserInterceptorFactory$1.processInvocation(InterceptorContext) line: 36

InterceptorContext.proceed() line: 288

SBInvocationInterceptor.processInvocation(InterceptorContext) line: 47

InterceptorContext.proceed() line: 288

InitialInterceptor.processInvocation(InterceptorContext) line: 21

InterceptorContext.proceed() line: 288

ChainedInterceptor.processInvocation(InterceptorContext) line: 61

ComponentDispatcherInterceptor.processInvocation(InterceptorContext) line: 53

InterceptorContext.proceed() line: 288

PooledInstanceInterceptor.processInvocation(InterceptorContext) line: 51

InterceptorContext.proceed() line: 288

CMTTxInterceptor.invokeInCallerTx(InterceptorContext, Transaction, EJBComponent) line: 202

CMTTxInterceptor.required(InterceptorContext, EJBComponent, int) line: 306

CMTTxInterceptor.processInvocation(InterceptorContext) line: 190

InterceptorContext.proceed() line: 288

EJBRemoteTransactionPropagatingInterceptor.processInvocation(InterceptorContext) line: 80

InterceptorContext.proceed() line: 288

CurrentInvocationContextInterceptor.processInvocation(InterceptorContext) line: 41

InterceptorContext.proceed() line: 288

LoggingInterceptor.processInvocation(InterceptorContext) line: 59

InterceptorContext.proceed() line: 288

EjbExceptionTransformingInterceptorFactories$1.processInvocation(InterceptorContext) line: 65

InterceptorContext.proceed() line: 288

NamespaceContextInterceptor.processInvocation(InterceptorContext) line: 50

InterceptorContext.proceed() line: 288

AdditionalSetupInterceptor.processInvocation(InterceptorContext) line: 32

InterceptorContext.proceed() line: 288

TCCLInterceptor.processInvocation(InterceptorContext) line: 45

InterceptorContext.proceed() line: 288

ChainedInterceptor.processInvocation(InterceptorContext) line: 61

ViewService$View.invoke(InterceptorContext) line: 165

LocalEjbReceiver.processInvocation(EJBClientInvocationContext, EJBReceiverInvocationContext) line: 179

*** The method below has references to my internal objects in this.parameters. The method above does not. ***

EJBClientInvocationContext.sendRequest() line: 179

TransactionInterceptor.handleInvocation(EJBClientInvocationContext) line: 43

EJBClientInvocationContext.sendRequest() line: 181

ReceiverInterceptor.handleInvocation(EJBClientInvocationContext) line: 128

EJBClientInvocationContext.sendRequest() line: 181

EJBInvocationHandler<T>.doInvoke(EJBInvocationHandler<T>, boolean, T, Method, Object[], EJBClientContext) line: 136

EJBInvocationHandler<T>.doInvoke(T, Method, Object[]) line: 121

EJBInvocationHandler<T>.invoke(Object, Method, Object[]) line: 104

$Proxy12.myMethod(MyObj) line: not available

MyEjbDelegate(MentorDelegate).myMethod(MyObj) line: 1190

Thanks

Kelly

1. Re: Losing objects during serialization...

jaikiran Jun 19, 2012 12:11 AM (in response to kdolan1)

What exactly is the type of the objects/variables that go null? Also if possible, can you attach a small reproducible application?
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2. Re: Losing objects during serialization...

kdolan1 Jun 19, 2012 8:20 AM (in response to jaikiran)

The objects are of type org.apache.xerces.dom.DocumentImpl and org.apache.xerces.dom.DeferredDocumentImpl.

In putting together some additional information, I wonder if I have stumbled onto the reason. The MyObj class is a subclass and the 2 variables in question are actually owned by a parent class that is NOT serializable (this I just noticed now).
Yesterday, I ran into http://docs.oracle.com/javase/6/docs/api/java/io/Serializable.html which talks to subtypes of non-serializable classes. The parent class has other variables and these are cloned correctly but they are set in its no-arg constructor whereas the 2 variables in question are not. For example:

public abstract class MyBaseObj {
   private Document docImpl;
   private Document deferredDocImpl;
   private List aList;
   private Map aMap;

public MyBaseObj() {
      aList = new ArrayList();
      aMap = new HashMap();
   }
}
public class MyObj extends MyBaseObj implements Serializable {
   // its vars, constructor and methods - none of which take responsibility for re-setting the docImpl or deferredDocImpl classes
}

MyObj is the object passed across an EJB boundary and therefore serialized. BTW - I also bet the only reason I think the aList and aMap variables are re-set correctly are because they are empty collections when I make the EJB call. I bet if they contained items, the items would be gone.

Do you agree?
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3. Re: Losing objects during serialization...

jaikiran Jun 19, 2012 8:38 AM (in response to kdolan1)

Yes, you are right. The entire object hierarchy is expected to be serializable. Having said that, I would think that throwing a NotSerailizableException would have been more appropriate in cases like these.
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