Using EL Implicit Objects

Context

Implicit objects providing access to scoped variables

Implicit Object	Description
`pageScope`	Provides access to a collection of all page scope objects.
`requestScope`	Provides access to a collection of all request scope objects.
`sessionScope`	Provides access to a collection of all session scope objects.
`applicationScope`	Provides access to a collection of scoped variables from the application's scope.

Overview

The EL can be used directly in template text, be it inside the body of a custom or standard actions or in template text outside of any action. EL expressions also can be used in any attribute that can accept a run-time expression, be it a standard action or a custom action.

Types of EL Implicit Objects

Sample Code

Implicit Object	Description
`pageContext`	Provides access to the context for the JSP page.

To obtain the request URI, you use:

${pageContext.request.requestURI}

Sample Code

Implicit Object	Description
`param`	Maps a request parameter name to a single value.
`paramValues`	Maps a request parameter name to an array of values.
`header`	Maps a request header name to a single value.
`headerValues`	Maps a request header name to an array of values.
`cookie`	Maps a cookie name to a single cookie.
`initParam`	Maps a context initialization parameter name to a single value.

To obtain the String value of a parameter, you use the param object :

${param.employeeId}

Sample Code

Implicit Object	Description
`pageScope`	Provides access to a collection of all page scope objects.
`requestScope`	Provides access to a collection of all request scope objects.
`sessionScope`	Provides access to a collection of all session scope objects.
`applicationScope`	Provides access to a collection of scoped variables from the application's scope.

To obtain a session scoped attribute, you use the sessionScope object :

${sessionScope.shoppingcart}

Procedure

Define the object or attribute you want to access.

You can do this in the source of a JSP or servlet.
Using the expression language syntax, request the required value.

Example

We want to set an attribute to the session with name user and value LocalAdministrator . This is done using the following code in the JSP file:

<%
   session.setAttribute("user", new User("LocalAdministrator"));
%>

From now on, we can access the value using the following expression:

Hello ${sessionScope.user.name}!

which is equal to

Hello ${user.name}!

Or even

Hello ${user["name"]}!

For the user object we defined a special class User , so here is its source code:

public class User {
 
        public User() {
 
        }
 
        public User(String name) {
                this.setName(name);
        }
 
        private String name;
 
        public String getName() {
                return name;
        }
 
        public void setName(String name) {
                this.name = name;
        }
}

To define an array, we put it under some scope so the EL can recognize it:

<%
        int[] numbersAttr={111,222,333,444};
        request.setAttribute("numbers", numbersAttr);
%>

The third number of the array is: ${numbers[2]}

You can also use the EL inside custom tag attributes like this:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:set var="x" value="1"/>
<c:out value="${x}"/>