Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  JavaServer Faces Technology

5.  Introduction to Facelets

6.  Expression Language

7.  Using JavaServer Faces Technology in Web Pages

8.  Using Converters, Listeners, and Validators

9.  Developing with JavaServer Faces Technology

10.  JavaServer Faces Technology: Advanced Concepts

11.  Using Ajax with JavaServer Faces Technology

12.  Composite Components: Advanced Topics and Example

13.  Creating Custom UI Components and Other Custom Objects

14.  Configuring JavaServer Faces Applications

15.  Java Servlet Technology

16.  Uploading Files with Java Servlet Technology

17.  Internationalizing and Localizing Web Applications

Part III Web Services

18.  Introduction to Web Services

19.  Building Web Services with JAX-WS

20.  Building RESTful Web Services with JAX-RS

21.  JAX-RS: Advanced Topics and Example

Part IV Enterprise Beans

22.  Enterprise Beans

23.  Getting Started with Enterprise Beans

24.  Running the Enterprise Bean Examples

25.  A Message-Driven Bean Example

26.  Using the Embedded Enterprise Bean Container

27.  Using Asynchronous Method Invocation in Session Beans

Part V Contexts and Dependency Injection for the Java EE Platform

28.  Introduction to Contexts and Dependency Injection for the Java EE Platform

29.  Running the Basic Contexts and Dependency Injection Examples

30.  Contexts and Dependency Injection for the Java EE Platform: Advanced Topics

Using Alternatives in CDI Applications

Using Specialization

Using Producer Methods, Producer Fields, and Disposer Methods in CDI Applications

Using Producer Methods

Using Producer Fields to Generate Resources

Using a Disposer Method

Using Predefined Beans in CDI Applications

Using Events in CDI Applications

Defining Events

Using Observer Methods to Handle Events

Firing Events

Using Interceptors in CDI Applications

Using Stereotypes in CDI Applications

31.  Running the Advanced Contexts and Dependency Injection Examples

Part VI Persistence

32.  Introduction to the Java Persistence API

33.  Running the Persistence Examples

34.  The Java Persistence Query Language

35.  Using the Criteria API to Create Queries

36.  Creating and Using String-Based Criteria Queries

37.  Controlling Concurrent Access to Entity Data with Locking

38.  Using a Second-Level Cache with Java Persistence API Applications

Part VII Security

39.  Introduction to Security in the Java EE Platform

40.  Getting Started Securing Web Applications

41.  Getting Started Securing Enterprise Applications

42.  Java EE Security: Advanced Topics

Part VIII Java EE Supporting Technologies

43.  Introduction to Java EE Supporting Technologies

44.  Transactions

45.  Resources and Resource Adapters

46.  The Resource Adapter Example

47.  Java Message Service Concepts

48.  Java Message Service Examples

49.  Bean Validation: Advanced Topics

50.  Using Java EE Interceptors

Part IX Case Studies

51.  Duke's Bookstore Case Study Example

52.  Duke's Tutoring Case Study Example

53.  Duke's Forest Case Study Example



Using Decorators in CDI Applications

A decorator is a Java class that is annotated javax.decorator.Decorator and that has a corresponding decorators element in the beans.xml file.

A decorator bean class must also have a delegate injection point, which is annotated javax.decorator.Delegate. This injection point can be a field, a constructor parameter, or an initializer method parameter of the decorator class.

Decorators are outwardly similar to interceptors. However, they actually perform tasks complementary to those performed by interceptors. Interceptors perform cross-cutting tasks associated with method invocation and with the lifecycles of beans, but cannot perform any business logic. Decorators, on the other hand, do perform business logic by intercepting business methods of beans. This means that instead of being reusable for different kinds of applications as are interceptors, their logic is specific to a particular application.

For example, instead of using an alternative TestCoderImpl class for the encoder example, you could create a decorator as follows:

public abstract class CoderDecorator implements Coder {
    Coder coder;
    public String codeString(String s, int tval) {
        int len = s.length();

        return "\"" + s + "\" becomes " + "\"" + coder.codeString(s, tval) 
                + "\", " + len + " characters in length";

See The decorators Example: Decorating a Bean for an example that uses this decorator.

This simple decorator returns more detailed output than the encoded string returned by the CoderImpl.codeString method. A more complex decorator could store information in a database or perform some other business logic.

A decorator can be declared as an abstract class, so that it does not have to implement all the business methods of the interface.

In order for a decorator to be invoked in a CDI application, it must, like an interceptor or an alternative, be specified in the beans.xml file. For example, the CoderDecorator class is specified as follows:


If an application uses more than one decorator, the decorators are invoked in the order in which they are specified in the beans.xml file.

If an application has both interceptors and decorators, the interceptors are invoked first. This means, in effect, that you cannot intercept a decorator.