myjavahub4: Expression Language ( EL ) pageScope, requestScope, sessionScope, and applicationScope

Expression Language implicit objects

EL contains 11 implicit objects.

The power of EL is just because of these implicit objects only.

The following is the list of all EL implicit objects.

Implicit object	Description
1. pageScope	Scoped variables from page scope
2. requestScope	Scoped variables from request scope
3. sessionScope	Scoped variables from session scope
4. applicationScope	Scoped variables from application scope
5. param	Request parameters as strings
6. paramValues	Request parameters as collections of strings
7. header	HTTP request headers as strings
8. headerValues	HTTP request headers as collections of strings
9. initParam	Context-initialization parameters
10. cookie	Cookie values
11. pageContext	The JSP PageContext object for the current page

1.The Scope Objects:

The pageScope, requestScope, sessionScope, and applicationScope implicit objects are used to retrieve data from request, session,page,application scopes.

Ex:1 To access the value of session scoped attribute ‘x’ ${sessionScope.x}

It prints the value of request scoped attribute ‘x’

If there is no such type of attribute we will get blank space ${requestScope.x}

Ex:2 ${x}

Jsp container first checks in page scope for the attribute x .if it is available it prints attribute value. If it is not available then it will check in request scope followed by session and application scope. It simply acts aspageContext.findAttribute(String name); method.

Test.jsp

<%@ page isELIgnored="false" %>

pageContext.setAttribute ("x", 100);

pageContext.setAttribute ("y", 1000);

pageContext.setAttribute ("X", 10);