Expression Language (EL)

Expression Language (EL) is a scripting language used in web applications, particularly in Java-based technologies like JSF, JavaServer Pages (JSP), and other Java Enterprise Edition (Java EE) frameworks. EL provides a way to dynamically access and manipulate data within the application, making it a powerful tool for developing dynamic and data-driven web pages.

EL allows developers to access and manipulate data stored in Java objects dynamically. This includes retrieving values from Enterprise JavaBeans (EJBs), arrays, lists, and other data structures. EL is often embedded within the markup of web pages, enabling developers to seamlessly mix static content with dynamic data. It simplifies the process of displaying data retrieved from the backend.

EL expressions are enclosed in ${}. For example, ${user.name} might retrieve the "name" property of a user object.

Common Use Cases:

  • Displaying dynamic content on web pages.
  • Accessing and presenting data from backend Java objects.
  • Evaluating conditions and controlling the flow of the user interface.

Suppose you have a JSP page with a user object stored in the request scope:

<%@ page import="com.example.User" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>User Profile</title>
</head>
<body>
    <h1>Welcome, ${user.name}!</h1>
    <p>Email: ${user.email}</p>
    <!-- Other dynamic content -->
</body>
</html>

In this example, the EL expressions ${user.name} and ${user.email} retrieve and display the name and email properties of the user object.