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JSP Technology in the Java EE 5 Platform

The focus of Java EE 5 has been ease of development by making use of Java language annotations that were introduced by J2SE 5.0. JSP 2.1 supports this goal by defining annotations for dependency injection on JSP tag handlers and context listeners.

Another key concern of the Java EE 5 specification has been the alignment of its webtier technologies, namely JavaServer Pages (JSP), JavaServer Faces (JSF), and JavaServer Pages Standard Tag Library (JSTL).
The outcome of this alignment effort has been the Unified Expression Language (EL), which integrates the expression languages defined by JSP 2.0 and JSF 1.1.
The main key additions to the Unified EL that came out of tbe alignment work have been:

  • A pluggable API for resolving variable references into Java objects and for resolving the properties applied to these Java objects,
  • Support for deferred expressions, which may be evaluated by a tag handler when needed, unlike their regular expression counterparts, which get evaluated immediately when a page is executed and rendered, and
  • Support for lvalue expression, which appear on the left hand side of an assignment operation. When used as an lvalue, an EL expression represents a reference to a data structure, for example: a JavaBeans property, that is assigned some user input.

The new Unified EL is defined in its own specification document, which is delivered along with the JSP 2.1 specification.
Thanks to the Unified EL, JSTL tags, such as the JSTL iteration tags, can now be used with JSF components in an intuitive way.

JavaServer Pages which is widely known and pronounced as JSP is a technology that works at server side. This Java Technology allows Java Developers to create pages in run-time environment whenever web client send request for certain page to server. JSP does this with supporting XML and hyper text document types. JSP pages are loaded at the server and executed from Java Server packet. This server packet is called J2EE Web Application.

This Java Technology helps Java Developers to embed code in to static web pages and allow them to be compiled at run time when any request arrives. Java Server pages works very closer and with the support provided by JVM (Java Virtual Machine) which is integrated with host operating system which can be vary from terminal to terminal.

There are basically two terminologies are there which are used when discussing JSP. One is Scriptlet and Markup through HTML or XML. These both terms indicates two different syntax used in JSP.

Scriptlet code block do not require to be completed in the immediate block but it can be completed in the later block. JSP code evaluation, validation and compilation is done dynamically which means run time. This run time compilation is not getting repeated every time but only when any change to code happens. Java Developers should be aware of the thing that JSP syntax adds additional XML tags as a part of JSP action.

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