java对象的getClass（）方法返回null

Question

My understanding is if a java object xx is not null there must be corresponding Class object for that object that can get using getClass() method, but some time this method returns null at run time that is very strange.

Example :

The object (oldFact) is serializble object that is referenced in ExternalFactUpdateDroolsEvent class as blew, this call get serialized and deserilized in it's excution process, means first many objects of type ExternalFactUpdateDroolsEvent get serialized and latter get desterilized before execution, in this process some time oldFact object returns null Class object that is causing problem.

My question is if an object is not null how getClass() method returns null ? Is this some thing related to deserilized object that in not properly initializing / instantiating or some thing else, these object might be getting serialized from different JVM and then getting executed on one JVM.

public class ExternalFactUpdateDroolsEvent implements DroolsEvent {

    private static final long serialVersionUID = -8225631607832350264L;

    private Object oldFact;

    public ExternalFactUpdateDroolsEvent(Object oldFact) {
        this.oldFact = oldFact;
        this.updatedFact = updatedFact;
    }

    public void executeAction(StatefulKnowledgeSession ksession) {
        // some time getClass() returns null that is strange  
        Class factClass = oldFact.getClass();

        ........................
    }

    ......................
}

Adding more content:

I am sure oldFact is not null because no nullPointer exception on oldFact.getClass(); call, the Class objecr factClass is being passed to other mentod where null is being asserted that's where we exception is throwing. See the code and exception as below. I appreciate your help in advance.

Answer 1

Let me guess that you receive a NullPointerException in this line:

Class factClass = oldFact.getClass();

Due to the fact, that getClass() can't return null ( EDIT: Even if getClass() would return null, that wouldn't cause a NullPointerException), oldFact must be the one which is null.

Answer 2

the whole point is, oldfact is null because when you send a handle in ExternalFactUpdateDroolsEvent you send a null pointer so oldfact remains a null object, so when you type oldfact.getclass() there is nothing to get

edit--

or this happens if you call method executeaction before calling ExternalFactUpdateDroolsEvent

Answer 3

Altough a bit late to the party, I just saw this searching for the same answers. Shouldn't private Object oldFact; be initialized as a new Object?

private Object oldFact;

to:

private Object oldFact = new Object();