Expression tag allow the developer to embed any Java expression and is short for out.println().

A semicolon ( ; ) does not appear at the end of the code inside the tag.

e.g.to show the current date and time.

Date : <%= new java.util.Date() %>

Directive tag

Direcitve tag ( <%@ directive...>)

A JSP directive gives special information about the page to JSP Engine.

Three main types of directives are:

1)     page - processing information for this page.
2)     Include - files to be included.
3)     Tag library - tag library to be used in this page.

Directives do not produce any visible output when the page is requested but change the way the JSP Engine processes the page.

e.g.,you can make session data unavailable to a page by setting a page directive (session) to false.

1. Page Directive

This directive has 11 optional attributes that provide the JSP Engine with special processing information. The 11 different attributes with a brief description is decribe in table given below:

Language	Which language the file uses.	<%@ page language = "java" %>
Extends	Superclass used by the JSP engine for the translated Servlet.	<%@ page extends = "com.taglib... %>
import	Import all the classes in a java package into the current JSP page. This allows the JSP page to use other java classes.	<%@ page import = "java.util.*" %>
session	oes the page make use of sessions. By default all JSP pages have session data available. There are performance benefits to switching session to false.	Default is set to true.
buffer	Controls the use of buffered output for a JSP page. Default is 8kb	<%@ page buffer = "none" %>
autoFlush	Flush output buffer when full.	<%@ page autoFlush = "true" %>
isThreadSafe	Can the generated Servlet deal with multiple requests? If true a new thread is started so requests are handled simultaneously.
info	Developer uses info attribute to add information/document for a page. Typically used to add author,version,copyright and date info.	<%@ page info = "visualbuilder.com test page,copyright 2001. " %>
errorPage	Different page to deal with errors. Must be URL to error page.	<%@ page errorPage = "/error/error.jsp" %>
IsErrorPage	This flag is set to true to make a JSP page a special Error Page. This page has access to the implicit object exception (see later).
contentType	Set the mime type and character set of the JSP.

2. Include directive

It allows a JSP developer to include contents of a file inside another. Typically include files are used for navigation,headers,tables and footers that are common to multiple pages.

Two examples of using include files:

This includes the html from privacy.html found in the include directory into the current jsp page.

<%@ include file = "include/privacy.html" %>

or to include a naviagation menu (jsp file) found in the current directory.

<%@ include file = "navigation.jsp" %>

3. Tag Lib directive

A tag lib is a collection of custom tag that can be used by the page.

<%@ taglib uri = "tag library URI" prefix = "tag Prefix" %>

Custom tag were introduced in JSP 1.1 and allow JSP developer to hide complex server side code from web designers

Scriptlet tag

Scriptlet tag ( <% ... %> )

Between <% and %> tags,any valid Java code is called a Scriptlet. This code can access any variable or bean declared. For example,to print a variable.

<%
�� String username = "visualbuilder" ;
��out.println ( username ) ;
� %>

Action tag

There are three main roles of action tag :
1)��It enable the use of server side Javabeans
2)��It transfer control between pages
3)��Browser independent support for applets.

Javabeans

A Javabeans is a special type of class that has a number of methods. The JSP page can call these method so can leave most of the code in these Javabeans. For example,if you wanted to make a feedback form that automatically sent out an email. By having a JSP page with a form,when the visitor presses the submit button this send the details to a Javabean that sends out the email. This way there would be no code in the JSP page dealing with sending emails (JavaMail API) and your Javabeans could be used in another page (promoting reuse).

To use a Javabeans in a JSP page use the following syntax:

The following is a list of Javabean scopes:

page - valid until page completes.
request - bean instance lasts for the client request
session - bean lasts for the client session.
application - bean instance created and lasts until application ends.

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