Nuts and Bolts of Java EE 7 Interceptors

2. Nuts and Bolts of Java EE 7 Interceptors Marina Vatkina, Oracle Emmanuel Bernard, Red Hat

3. Program Agenda • Overview • Changes • Why Bean Validation uses interceptors • New features deep dive • JTA declarative transactions with interceptors

4. Interceptors 1.2 Overview • Maintenance update to the Interceptors 1.1 (JSR-318) • Part of Java EE 7 • Contains common rules for Java EE interceptors • All definitions and rules in one place • Used by developers and container providers

5. Interceptors 1.2 Feature Summary • Interceptor Bindings are now part of the Interceptors spec • Specification covers interceptors associated using @Interceptorsand @InterceptorBindingannotation • Specification document has better flow and many examples • Added AroundConstructLifecycle interceptor • Introduced standard Priorityranges • Simplified rules for interceptor method signatures

6. Interceptors 1.2 Interceptor Bindings are now part of the Interceptors spec • Moved Interceptor Bindings chapter from the CDI spec into the Interceptors spec • Improved document flow: common rules and rules specific to binding type • Moved ejb-jar.xml deployment descriptor elements back to the EJB spec • No need to search in 2 specifications for answers • Added examples

7. Why Bean Validationneeds interceptors

8. Bean Validation What is Bean Validation • Define and declare constraints on objects • Annotation based • Extensible classUser { @NotNull@Size(max=100) public String getFirstname() {...} @SSN//custom constraint public String getSocialSecurityNumber() { ... } }

9. Bean Validation What’s new in Bean Validation 1.1 • Validation of parameters and return values upon method call @RequestScoped classUserService { @NotNull List<User> getPersonAboveAge(@Min(18) int age) { ... } }

10. Bean Validation What’s new in Bean Validation 1.1

11. Bean Validation The inside story of method validation • Bean Validation offers contracts to validate methods • Some interception technology needs to call them • Use a CDI portable extension to add interceptor to constrained methods • No proprietary hook • Every integration points are standard Java EE

12. Bean Validation Interceptors: need for improvement • Java EE was missing a thing or two on interceptors • Cross expert group work • Bean Validation, CDI, Interceptor, EJB, Java EE

13. Bean Validation Validating constructor • Bean Validation also validates constructors • CDI calls Bean Validation when it calls new • Need for an @AroundConstruct

14. Bean Validation Ordering validators • Validation should happen as late as possible • after security and transaction checks • limit risk of parameter value mutation • Introduction of @Priority

15. Bean Validation @Priority • Salient (aka number based priority) • Defines ranges • Application and libraries put their interceptors at the right place • Considered alternatives • e.g. partial ordering • Bean Validation priority • Interceptor.Priority.PLATFORM_AFTER+800

16. Bean Validation Putting it all together • Use CDI portable extension • Attach method and constructor interceptor programmatically • Interceptor has expected priority • Same logic implementable by other platforms

17. New features deep dive

18. Interceptors 1.2 AroundConstruct interceptor • New lifecycle callback interceptor type • Can be declared only on an interceptor class • When invoked: • Interceptor instances are created and injection is completed on them • The last InvocationContext.proceed creates the target instance • Can access it afterwards via InvocationContext.getTarget • AroundConstruct completes • Injection is completed on the target instance • PostConstruct is invoked (if defined)

19. Interceptors 1.2 AroundConstruct interceptor @InterceptorBinding @Target(CONSTRUCTOR) public @interface ValidateConstructor {} @ValidateConstructor @Interceptor public class ValidationInterceptor { @AroundConstruct public void validate_constructor(InvocationContext ctx){...} ... }

20. Interceptors 1.2 AroundConstruct interceptor public class SomeBean { @ValidateConstructor @Inject SomeBean(...) { ... } public void someMethod() { ... } }

21. Interceptors 1.2 Ordering Interceptors using the Priority Annotation • Priority annotation enables and orders interceptors bound to a component using interceptor binding • Interceptors with smaller priority values are called first • Global ordering of interceptors bound to a component using interceptor binding • Undefined if more than one interceptor has the same priority • Ignored if used on interceptors bound to a component using the Interceptors annotation.

22. Interceptors 1.2 Standard Priority ranges • Predefined values: • Interceptor.Priority.PLATFORM_BEFORE = 0 • Interceptor.Priority.LIBRARY_BEFORE = 1000 • Interceptor.Priority.APPLICATION = 2000 • Interceptor.Priority.LIBRARY_AFTER = 3000 • Interceptor.Priority.PLATFORM_AFTER = 4000 • Define ranges between the values

23. Interceptors 1.2 Ordering Interceptors using the Priority Annotation @Priority(Interceptor.Priority.LIBRARY_BEFORE+10) @Validation @Interceptor public class ValidationInterceptor { ... } OR @Monitored @Interceptor @Priority(2100) public class MonitoringInterceptor{ ... }

24. Interceptors 1.2 Ordering Interceptors using theInterceptors Annotation @Interceptors({InterceptorA.class, InterceptorB.class}) @Stateless public classMyBean{ public void method1(…) {…} @Interceptors({InterceptorC.class, InterceptorD.class}) public void method2(…) {…} }

25. Interceptors 1.2 Ordering Interceptors using theInterceptors Annotation @Interceptors({InterceptorA.class, InterceptorB.class}) @Stateless public classMyBean{ public void method1(…) {…} @ExcludeClassInterceptors @Interceptors({InterceptorC.class, InterceptorD.class}) public void method2(…) {…} }

26. Interceptors 1.2 Common Ordering Rules • @Interceptors interceptors (if any) • Ordered as specified • @InterceptorBindinginterceptors (if any) • Ordered using @Priority • Interceptor methods of the target bean class (if any) • Superclass first • Target bean method or constructor (if applicable)

27. Interceptors 1.2 Simplified rules for interceptor method signatures • Around-invoke or around-timeout are simple: @AroundInvoke @AroundTimeout public Object monitor(InvocationContext ctx) throws Exception{ // do something return ctx.proceed(); }

28. Interceptors 1.2 Simplified rules for interceptor method signatures • Lifecycle callback required boilerplate code: @PostConstruct public void monitor_create(InvocationContext ctx) { try { // do something ctx.proceed(); // InvocationContext.proceed() throws Exception } catch (Exception e) { throw new RuntimeException(e); }

29. Interceptors 1.2 Simplified rules for interceptor method signatures • Any interceptor @AroundInvoke @PostConstruct @PreDestroy public Object monitor(InvocationContext ctx) throws Exception { // do something return ctx.proceed(); // lifecycle callback returns null }

30. JTA declarative transactions with interceptors

31. JTA declarative transactions with interceptors @Transactional • Container managed transaction demarcation on CDI managed beans • Modeled after EJB CMT • Declarative transaction demarcation via simple annotation • Default TxType.REQUIRED • Ability to specify exception handling behavior for marking transactions for rollback declaratively

32. JTA declarative transactions with interceptors @Transactional • An interceptor • Can be applied to a class or a method of a CDI managed bean • Not allowed on EJBs • Priority(Interceptor.Priority.PLATFORM_BEFORE + 200)

33. JTA declarative transactions with interceptors @Transactional @Transactional public class Account { public int get(String param1, int param2) { } @Transactional(value = Transactional.TxType.REQUIRES_NEW, rollbackOn ={SQLException.class}, dontRollbackOn ={SQLWarning.class}) public void update(String param1, int param2) { }

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35. Q&A

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