constructor_and_method_level_interceptors.adoc

Constructor- and Method-level Interceptors

Method-level interceptors are interceptor classes directly associated with a specific business or timeout method of the target class. Constructor-level interceptors are interceptor classes directly associated with a constructor of the target class.

For example, an around-invoke interceptor method may be applied only to a specific business method of the target class— independent of the other methods of the target class—by using a method-level interceptor. Likewise, an around-timeout interceptor method may be applied only to a specific timeout method on the target class, independent of the other timeout methods of the target class.

Method-level interceptors may not be associated with a lifecycle callback method of the target class.

The same interceptor may be applied to more than one business or timeout method of the target class.

If a method-level interceptor is applied to more than one method of a associated target class this does not affect the relationship between the interceptor instance and the target class—only a single instance of the interceptor class is created per target class instance.

In the following example only the placeOrder method will be monitored:

public class ShoppingCart {
    @Monitored
    public void placeOrder() {
         ...
    }
}

In the following example, the MyInterceptor interceptor is applied to a subset of the business methods of the session bean. Note that the created and removed methods of the MyInterceptor interceptor will not be invoked:

public class MyInterceptor {
    ...
    @AroundInvoke
    public Object around_invoke(InvocationContext ctx) { ... }

     @PostConstruct
     public void created(InvocationContext ctx) { ... }

     @PreDestroy
     public void removed(InvocationContext ctx) { ... }
}

@Stateless
public class MyBean {
     @PostConstruct
     void init() { ... }

     public void notIntercepted() { ... }

     @Interceptors(org.acme.MyInterceptor.class)
     public void someMethod() { ... }

     @Interceptors(org.acme.MyInterceptor.class)
     public void anotherMethod() { ... }
}

In the following example, the ValidationInterceptor interceptor interposes on the bean constructor only, and the validateMethod interceptor method will not be invoked:

@Inherited
@InterceptorBinding
@Target({CONSTRUCTOR, METHOD})
@Retention(RUNTIME)
public @interface ValidateSpecial {}

@ValidateSpecial
public class ValidationInterceptor {
     @AroundConstruct
     public void validateConstructor(InvocationContext ctx) { ... }

     @AroundInvoke
    public Object validateMethod(InvocationContext ctx) { ... }
}

public class SomeBean {
    @ValidateSpecial
    SomeBean(...) {
        ...
    }

    public void someMethod() {
        ...
    }
}

In the following example, the validateConstructor method of the ValidationInterceptor interceptor interposes on the bean constructor, and the validateMethod method of the interceptor interposes on the anotherMethod business method of the bean.

public class SomeBean {
    @ValidateSpecial
    SomeBean(...) {
        ...
    }

    public void someMethod() {
        ...
    }

    @ValidateSpecial
    public void anotherMethod() {
        ...
    }
}