Hi, thanks for your reply, I was having a look at annotation_attribute, annotationwriter and annotationattribute, and now I've got a doubt: is the annotation only stored in the class file? Because what I'd like to obtain is to "inject" an annotation into a class (Runtime retention) when the class is loaded, without modifying the class file. But if I use the ClassFile object I have to modify the class file on the disk, is this correct? Is there a way to add an annotation at load time? Thanks, Luca View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4130748#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...