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

Immediate and Deferred Evaluation Syntax

Immediate Evaluation

Deferred Evaluation

Value and Method Expressions

Value Expressions

Referencing Objects Using Value Expressions

Referring to Object Properties Using Value Expressions

Where Value Expressions Can Be Used

Method Expressions

Parameterized Method Calls

Defining a Tag Attribute Type

Literal Expressions


Reserved Words

Examples of EL Expressions

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

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



Overview of the EL

The EL allows page authors to use simple expressions to dynamically access data from JavaBeans components. For example, the test attribute of the following conditional tag is supplied with an EL expression that compares 0 with the number of items in the session-scoped bean named cart.

<c:if test="${sessionScope.cart.numberOfItems > 0}">

JavaServer Faces technology uses the EL for the following functions:

  • Deferred and immediate evaluation of expressions

  • The ability to set as well as get data

  • The ability to invoke methods

See Using the EL to Reference Managed Beans for more information on how to use the EL in JavaServer Faces applications.

To summarize, the EL provides a way to use simple expressions to perform the following tasks:

  • Dynamically read application data stored in JavaBeans components, various data structures, and implicit objects

  • Dynamically write data, such as user input into forms, to JavaBeans components

  • Invoke arbitrary static and public methods

  • Dynamically perform arithmetic operations

The EL is also used to specify the following kinds of expressions that a custom tag attribute will accept:

  • Immediate evaluation expressions or deferred evaluation expressions. An immediate evaluation expression is evaluated at once by the underlying technology, such as JavaServer Faces. A deferred evaluation expression can be evaluated later by the underlying technology using the EL.

  • Value expression or method expression. A value expression references data, whereas a method expression invokes a method.

  • Rvalue expression or lvalue expression. An rvalue expression can only read a value, whereas an lvalue expression can both read and write that value to an external object.

Finally, the EL provides a pluggable API for resolving expressions so custom resolvers that can handle expressions not already supported by the EL can be implemented.