Expression Language (EL) in JSP

Expression Language (EL) was introduced in JSP 2.0 version. EL is the easiest way of invoking java code. EL expressions increase JSP code readability and reusability. EL expressions are always within curly braces and prefixed with the dollar sign.

Expression Language Syntax

${expr}

${ expr. expr }

${ expr [expr] }

expr can be any one of the following

Java expression resulting into any value.
Java variable containing any value.

In EL there are two access operators.

. (dot) operator
[ ] (bracket) operator

Example

<html>

${100}<br>

${44.13}<br>

${"Hello"}<br>

${true}<br>

${5+7}<br>

${6/3}<br>

${5>2}

</body>

</html>

Implicit Objects in Expression Language

EL implicit and JSP implicit objects are different except pageContext. pageContext implicit object is same in and refers to the object of javax.servlet.jsp.PageContext. All the EL implicit objects are of type java.util.Map.

Implicit Objects	Usage
applicationScope	A java.util.Map having the values of named attributes in application scope
cookie	A java.util.Map having cookie names and their values.
header	A java.util.Map that links parameter names to String arrays corresponding to ServletRequest.getParameterValues(String name)
headerValues	A java.util.Map having header names and their values.
initParam	A java.util.Map having context initialization parameter names and their values.
pageContext	The JSP PageContext object.
pageScope	A java.util.Map having the values of named attributes in page scope
param	A java.util.Map having the values of named attributes in
paramValues	A java.util.Map that links parameter names to their ServletRequest.getParameter(String name)
requestScope	A java.util.Map having the values of named attributes in request scope
sessionScope	A java.util.Map having the values of named attributes in session scope

Example for expression language with implicit objects

login.html

<html>

<h1>WELCOME TO LOGIN PAGE</h1>

FIRST NAME:<input type="text" name="fname">

LAST NAME:<input type="text" name="lname">

PRIMARY PHONE:<input type="text" name="ph">

SECONDARY PHONE:<input type="text" name="ph">

</form>