Expression Language(EL)

In this section, you will get a brief description about Expression Language of JSF.

Expression Language is used to access the JavaBeans component in the JSF web application.

The syntax of the EL expression is :

# { expression }

It is similar to JSP expression language but have following differences from it :

The syntax of both contains { }curly braces inside it expression resides. But JSP EL starts with $ and JSF EL starts with #.
The value binding methods of JSF don't support expression language methods of JSP.

The JSF EL supports following literals :

Boolean: true and false
Integer: as in Java
Floating point: as in Java
String: with single and double quotes; " is escaped as \", ' is escaped as \', and \ is escaped as \\.
Null: null

The Operators supported by JSF EL with operators precedence , from left to right(highest to lowest), is given below :

Some of Example of EL is given below :

JSF EL Expression	Result
${1 > (4/2)}	false
${4.0 >= 3}	true
${100.0 == 100}	true
${(10*10) ne 100}	false
${?a? < ?b?}	true
${?hip? gt ?hit?}	false
${4 > 3}	true
${1.2E4 + 1.4}	12001.4
${3 div 4}	0.75
${10 mod 4}	2
${!empty param.Add}	False if the request parameter named Add is null or an empty string.
${pageContext.request.contextPath}	The context path
${sessionScope.cart.numberOfItems}	The value of the numberOfItems property of the session-scoped attribute named cart.
${param[?mycom.productId?]}	The value of the request parameter named mycom.productId.
${header["host"]}	The host
${departments[deptName]}	The value of the entry named deptName in the departments map
${requestScope[?javax.servlet.forward.servlet_path?]}	The value of the request-scoped attribute named javax.servlet.forward.servlet_path
#{customer.lName}	Gets the value of the property lName from the customer bean during an initial request. Sets the value of lName during a postback
#{customer.calcTotal}	The return value of the method calcTotal of the customer bean.

JSF Expression Language(EL)