Why Am I Getting a ClassCastException When Casting Objects Loaded by Different ClassLoaders in Java?

ClassCastException When Casting to Expected Class

When working with multiple Java projects, you may encounter a ClassCastException when casting an object to its expected class despite verifying its class type. This typically occurs due to differences in classloading mechanisms.

In your case, you have two separate projects with different versions of the dynamicbeans.DynamicBean2 and dynamic.Validator classes. You dynamically load these classes into your Form project and create instances of them. However, during the lifecycle of your Form project, you encounter a ClassCastException when trying to cast an object retrieved from the session back to the expected DynamicBean2 class.

This exception occurs because the object you retrieved from the session was loaded by a different classloader than the one that loaded the DynamicBean2 class in your Form project. Even though the classes have the same name, they are actually different Class objects in the JVM.

To resolve this issue, you need to ensure that the object you retrieve from the session is loaded by the same classloader that loaded the DynamicBean2 class in your Form project. There are several possible solutions:

1. Change the context class loader manually. This requires obtaining a reference to an appropriate class loader, which may not be feasible in your situation.


2. Make sure the class is loaded by a class loader higher in the hierarchy. This ensures that both the instance you retrieve from the session and the DynamicBean2 class are loaded by the same parent class loader.


3. Serialize and deserialize the object. This can be a workaround, but it's not the most efficient solution.

There may be other possible ways to address this issue specific to your application's context. Consult the provided article on classloading in WebSphere for further information and potential solutions.

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