Interceptor

Overview

Package javax.interceptor, annotations on intercepting method

• @AroundConstruct - call back after construction of target class

  • Must call Invocation.proceed, or target instance not created

  • Construct sequence:

    1. DI completed for all interceptors associated with target class

    2. @AroundConstruct method called

    3. all associated @AroundConstruct interceptor called Invocation.proceed

    4. target class created

    5. target class constructor injection performed

    6. @PostConstruct called

• @AroundInvoke

  • @AroundInvoke

• • • public void interceptOrder(InvocationContext ctx) {...}

• @AroundTimeout - interposing on timeout methods for enterprise bean timers

  • @AroundTimeout

• • • protected void timeoutInterceptorMethod(InvocationContext ctx) { ... }

• @PostConstruct (allows only one)

  • @PostConstruct

• • • void initialize() { ... }

• @PreDestroy (allows only one)

  • @PreDestroy

• • • void cleanup(InvocationContext ctx) { ... }

Interceptor classes

• @Interceptor (optional, not required to be annotated)

• default constructor

• may be target for DI

• have the same lifecycle as the associated target class

• class annotate with interceptor type

• method annotate with interceptor annotation

• one class may be declare multiple interceptor binding types

• multiple interceptor class may declare one interceptor binding type

@Logged

@Interceptor

public class LoggingInterceptor {

@AroundInvoke

public Object logInvocation(InvocationContext ctx) throws Exception { ... }

...

}

Multiple interceptors

• @Interceptors({PrimaryInterceptor.class, SecondaryInterceptor.class, LastInterceptor.class})

  • public void updateInfo(String info) { ... }

• same InterceptorContext is passed to each interceptor, its contextData can be used to share data

Modify parameter data

InterceptorContext.parameters

Binding

Define interceptor binding type

@InterceptorBinding

@Target({TYPE, METHOD})

@Retention(RUNTIME)

@Inherited

pubic @interface Logged { ... }

Interceptor can be applied to another interceptor binding type

@Logged

@InterceptorBinding

@Target({TYPE, METHOD}) // CONSTRUCTOR

@Retention(RUNTIME)

@Inherited

public @interface Secured { ... }

Invocation sequence

• defined in deployment descriptor (XML) first

• @Interceptors invoked by order of listing

• super class invoked first than sub class

• @Priority set sequence, smaller value invoked first