9 Expression Language

This chapter introduces the Expression Language (also referred to as the EL), which provides an important mechanism for enabling the presentation layer (web pages) to communicate with the application logic (managed beans). The EL is used by several JavaEE technologies, such as JavaServer Faces technology, JavaServer Pages (JSP) technology, and Contexts and Dependency Injection for Java EE (CDI). The EL can also be used in stand-alone environments. This chapter only covers the use of the EL in Java EE containers.

The following topics are addressed here:

• Overview of the EL

• Immediate and Deferred Evaluation Syntax

• Value and Method Expressions

• Operations on Collection Objects

• Operators

• Reserved Words

• Examples of EL Expressions

• Further Information about the Expression Language