Expression Language (EL) in JSP

Expression Language (EL) in JSP
Implicit Objects in Expression Language
Simple example of Expression Language that prints the name of the user
Example of Expression Language that prints the value set in the session scope
Precedence of Operators in EL
Reserve words in EL

The Expression Language (EL) simplifies the accessibility of data stored in the Java Bean component, and other objects like request, session, application etc.

There are many implicit objects, operators and reserve words in EL.

It is the newly added feature in JSP technology version 2.0.

Syntax for Expression Language (EL)

Implicit Objects in Expression Language (EL)

There are many implicit objects in the Expression Language. They are as follows:

Implicit Objects	Usage
pageScope	it maps the given attribute name with the value set in the page scope
requestScope	it maps the given attribute name with the value set in the request scope
sessionScope	it maps the given attribute name with the value set in the session scope
applicationScope	it maps the given attribute name with the value set in the application scope
param	it maps the request parameter to the single value
paramValues	it maps the request parameter to an array of values
header	it maps the request header name to the single value
headerValues	it maps the request header name to an array of values
cookie	it maps the given cookie name to the cookie value
initParam	it maps the initialization parameter
pageContext	it provides access to many objects request, session etc.

Simple example of Expression Language that prints the name of the user

In this example, we have created two files index.jsp and process.jsp. The index.jsp file gets input from the user and sends the request to the process.jsp which in turn prints the name of the user using EL.

index.jsp

<form action="process.jsp">
Enter Name:<input type="text" name="name" /><br/><br/>
<input type="submit" value="go"/>
</form>

process.jsp

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Example of Expression Language that prints the value set in the session scope

In this example, we printing the data stored in the session scope using EL. For this purpose, we have used sessionScope object.

index.jsp

<h3>welcome to index page</h3>
<%
session.setAttribute("user","sonoo");
%>

<a href="process.jsp">visit</a>

process.jsp

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Precedence of Operators in EL

There are many operators that have been provided in the Expression Language. Their precedence are as follows:

[] .

()

-(unary) not ! empty

* / div % mod

+ - (binary)

< <= > >= lt le gt ge

== != eq ne

&& and

|| or

Reserve words in EL

There are many reserve words in the Expression Language. They are as follows:

lt	le	gt	ge
eq	ne	true	false
and	or	not	instanceof
div	mod	empty	null

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JSP Tutorial

Expression Language (EL) in JSP

Syntax for Expression Language (EL)

Implicit Objects in Expression Language (EL)

Simple example of Expression Language that prints the name of the user

index.jsp

process.jsp

Example of Expression Language that prints the value set in the session scope

index.jsp

process.jsp

Precedence of Operators in EL

Reserve words in EL