Java注释和代码在运行时执行

Question

Annotations supposedly are markers/provide metadata, so for example how does the @RolesAllowed annotation in JAX-RS work? This annotation "executes" code since it checks that the user is authenticated and has the required roles, at runtime (when an annotated method is called).

Answer 1

No. There is code that checks if the annotation exists and performs operations based on it. The annotation itself just lies there. The code that performs the checking and operations is executed around the method call.