When are Java annotations executed?

Question

I am just looking to write some annotation which can execute at runtime, before or immediately after a service method is invoked.

I don\'t know if they are executed at r

Answer 1

It depends on retention policy attached with that annotation.

A retention policy determines at what point annotation should be discarded. Java defined 3 types of retention policies through java.lang.annotation.RetentionPolicy enumeration. It has SOURCE, CLASS and RUNTIME.

• Annotation with retention policy SOURCE will be retained only with source code, and discarded during compile time.

• Annotation with retention policy CLASS will be retained till
  compiling the code, and discarded during runtime.

• Annotation with retention policy RUNTIME will be available to the JVM through runtime.

The retention policy will be specified by using java built-in annotation @Retention, and we have to pass the retention policy type. The default retention policy type is CLASS.