ClassCastException issue

Question

I have the following code:

Object backingBean = facesContextHandler.getBackingBean("UserCredentialsBean");
UserCredentialsBean userCredentBean = (UserCredentialsBean) backingBean;

While I'm debugging it I have the following in my expressions view in Eclipse:

backingBean.getClass() -> myPackage.UserCredentialsBean

backingBean instanceOf myPackage.UserCredentialsBean -> false

So casting above fails...

How can this be?

Update: Additional "symptom": I get this issue after session timeout

Any ideas?

I reckon it could be helpful to have a stack trace. It's possible the OP missed something in his analysis, or perhaps there is more detail somewhere... There more info the better chance that someone can help — Java Drinker
– Java Drinker, Commented Apr 18, 2011 at 15:04
If "UserCredentialsBean" is stored in the session scope and your session times out, then it will be null. Is this what is happening? — Java Drinker
– Java Drinker, Commented Apr 18, 2011 at 15:16

billygoat · Accepted Answer · 2011-04-18 14:58:29Z

4

Interesting question. I can only think of two possibilities.

1- Null Object. instanceOf usually fails for null object. Just make sure that the bean is initialized.

2- Class Loader Issue. If two objects of same class are loaded by two different class loaders, then instanceOf will fail.

This is not an all inclusive list, just two things I could think of.

answered Apr 18, 2011 at 14:58

billygoat

22.1k5 gold badges43 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Andriy Sholokh Over a year ago

backingBean is not null. Eclipse shows its attributes as of UserCredentialsBean object with data populated.

Andriy Sholokh Over a year ago

Regarding Class Loader Issue... I should think how these could happen any ClassLoader issue.

billygoat Over a year ago

Then you might have to look in to the class loader issue. This is JSF application right and you are trying to get a backing bean within your applcation. ??

Java Drinker Over a year ago

The class loader issue is interesting, although a cast... hmm... What happens if you do a dynamic cast (using reflection). Get the Class object and then call the cast() method

Andriy Sholokh Over a year ago

Yes, correct. And one point... I get this issue after session timeout

|

Vladimir Dyuzhev · Accepted Answer · 2011-04-18 15:43:31Z

2

ClassLoader issue for sure. Most probably the application got redeployed (thus new classloader instance was created), but the old object remained either in (disk-serialized?) session or in memory.

Class name is the same, but class loader instance is different. Instanceof looks at complete class name AND equality of classloaders.

P.S. This is actually a quite common issue. It is often visible when a background thread wakes up only to find out that the application was redeployed, the thread's classloader is gone and then it throws either NoClassDefFound or ClassCast to the big amusement of developers who not always realize this is actually a zombie from the previous deployment, and trying to find a bug in their code.

edited Apr 18, 2011 at 15:43

answered Apr 18, 2011 at 15:33

Vladimir Dyuzhev

18.4k10 gold badges53 silver badges62 bronze badges

Collectives™ on Stack Overflow

ClassCastException issue

2 Answers 2

6 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related