j2ee: JSP Expression Language - concepts [3/27]

The JSP expression language was initially described in the Java Standard Tag Library. This is just a set of Custom Tag Libraries meant to standardize the most common functions needed in JSPs. The language is independent of JSP except for the set of implicit objects it defines, and can be reused elsewhere. The JSTL version 1.0 can be used in a JSP 1.2 container. In JSP 2.0, some changes were made to the language, and JSTL 1.1 incorporates those changes. JSP 2.0 is required for the JSP EL to be available outside of the JSTL tags.

The EL is based on:

• Available namespace (the PageContext attributes)
• Nested properties and accessors to collections
• Relational, logical and arithmetic operators.
• Extensible functions mapping into static methods in Java classes.
• A set of implicit objects

JSP EL is inspired by ECMAScript (a.k.a JavaScript) and XPath (XML)

JSP EL is meant to replace Java Code in JSPs, and with 2.0 it is available in attribute values and template text using the construct ${expr}