Differences between @Interceptors and @InterceptorBinding + @Logged?

Question

Seems there are two ways to binding interceptor to target class/method:

1. @Interceptors on target class/method
2. Declare a interceptor binding type(aka, a custom annotation annotated with @InterceptorBinding itself, for example @Logged), and using it on target class/method

I am using interceptor in CDI environment. My question is, does it is completely unnecessary to declare a extra interceptor binding type if I using @Interceptors to binding interceptor to my target methods?

If answer is yes, then why IntelliJ IDEA constantly complaint me a error

@Interceptor must specify at least one interceptor binding

when I am not annotating interceptor binding type on my interceptor?

If answer is no, I already binding my interceptor to target class/method with @Interceptors(arrayOfMyInceptor) directly, why declare a extra interceptor binding type and using it on my interceptor?

I search the web but cannt found anything about difference of this two approaches, hope SO can solve my problem.

Thank you for your patience.

Answer 1

The annotations @Interceptor and other costum annotations like @Logged are supposed to be invoked on a interceptor class, e.g.

@Logged
@Interceptor
@Priority(Interceptor.Priority.APPLICATION)
public class LoggedInterceptor implements Serializable { ... }

The annotation @InterceptorBinding has to be invoked on the annotation you want to create to make clear it's somewhat of a "interceptor qualifier".

@Inherited
@InterceptorBinding
@Retention(RUNTIME)
@Target({METHOD, TYPE})
public @interface Logged {
}

Then you can invoke the interceptor-binding annotation on a (managed) bean or its methods.

@Logged
public String pay() {...}

@Logged
public void reset() {...}

See the java tutorial for more help https://docs.oracle.com/javaee/7/tutorial/cdi-adv006.htm

EDIT

Because I misread your question, here's my edit: The annotation @Interceptors is like a collection of interceptors. By passing several interceptor classes (e.g. LoggedInterceptor from @Logged) to the value variable of the applied @Interceptors annotation all those inteceptor bindings are invoked:

@Interceptors({LoggedInterceptor.class,
OtherInterceptor.class,.....})

Thus you need at least one interceptor binding for @Interceptors

So you need an interceptor binding for the interceptor class itself but not for the target class since it's already mentioned in the @Interceptors annotation.

See the API documentation https://docs.oracle.com/javaee/7/api/javax/interceptor/Interceptors.html