JSP EL: It is a expression language which makes it easier for a programmer to fetch javabeans and various objects like request, session values on jsp. There are implicit objects also of EL. It simplifies the Presentation layer.
JSP EL starts with a "$" followed by a "{" and ends with a "}"
To use this we need to specify the isELIgnored attrbute of page directive.
<%@ page isELIgnored ="true|false" %gt;
If it is true, EL expressions are ignored when they appear in static text or tag attributes. If it is false, EL expressions are evaluated by the container.
Simple example:
${1+2-3}
Basic EL Operators: There are many airthmetic,logical,relational and conditional operator which can be used in EL.
( ): For subexpression to change the evaluation order
+: Addition
-: Subtraction
*: Multiplication
/: or div Division
%: or mod Modulo (remainder)
==: or eq Equality
!=: or ne Inequality
<: or lt Less than
>: or gt Greater than
<=: or le Less than or equal
>=: or gt Greater than or equal
&&: or and Logical AND
||: or or Logical OR
!: or not Unary Boolean complement
EL implicit variable
pageScope: page scope variable
requestScope: request scope variables
sessionScope: session scope variables
e.g We have set one variable in session scope:
<%
session.setAttribute("name","ank");
%>
Fetching on another page usin EL
${ sessionScope.name }
applicationScope: application scope variables
param: Request parameters
e.g <p>${param["name"]}</p>
paramValues: Request parameters as collections of strings
header: HTTP request headers
e.g <h3>${header["user-agent"]}</h3>
headerValues: HTTP request headers as collections of strings
initParam : Context-initialization parameters
cookie : Cookie values
pageContext : PageContext object