I have done further reading on how this is implemented by the compiler and finally found out the answer I was looking for. You can defenitely do that with javaassist. The key class is javassist.bytecode.SignatureAttribute. CtMethod method = .... | MethodInfo methodInfo = method.getMethodInfo(); | SignatureAttribute signatureAttribute = new SignatureAttribute(methodInfo.getConstPool(), | "()Ljava/util/List<Ljava/lang/String;>;"); | methodInfo.addAttribute(signatureAttribute); If your more interesed in reading the signature with the generics inside, you can use the methodInfo.getAttribute(SignatureAttribute.tag). I hope this helped. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4114787#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...