java.net.URLClassLoader doesn't add class annotations

Question

While developing a ant - task to autogenerate some gui - code for a project using annotations as I prefer a declarative approach I am using the java.net.URLClassLoader to dynamically add the classes to my class path.
When scanning the classes for class - level - annotations none of them is found though
they exists.
e.g.

@AutoGenerateGUI
class LoginBean

Has anyone else experienced this problem and can provide a solution?
(Subclassing the URLClassLoader to make the call to loadClass internally be treated as loadClass(Class clazz, true) didn't work neither)

Thanks to https://stackoverflow.com/users/1103872/marko-topolnik In Addition: Retrieving the annotations of the dynamically loaded classes always returned com.sun.proxy.$Proxy[x], so to get to the original annotation type I had to use the construct URLClassLoader loads Annotation as com.sun.$Proxy$27 iterating over the interfaces the proxy object implements. Though this should not be necessary, indeed other solutions e.g. using instanceof failed.

Answer 1

My guess would be that AutoGenerateGUI is your custom annotation, and you haven't specified the correct retention policy for it. The default is RetentionPolicy.CLASS, which will discard the annotation after loading the class. The annotation will not be available through reflection at runtime.