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JSP Directives

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JSP directives

In jsp directives are used to tells the web container which is translate a JSP page in servlet.

Three types Directives:

page directive
include directive
taglib directive

Syntax used

<%@ directive attribute="value" %>

JSP page directive

In page directive is defines of the attributes which apply in an entire JSP page.

Syntax used

<%@ page attribute="value" %>

Attributes used

import
contentType
extends
info
buffer
language
isELIgnored
isThreadSafe
autoFlush
session
pageEncoding
errorPage
isErrorPage

import

It is used to import class which is connect of all package with similar to import keyword in java class or interface.

Example

	<html>  
    <body>
    <%@ 

page import="java.util.Date" %>  
    Today is: <%= new Date( ) %>   
    </body>  
    </html>

contentType

In contentType attribute is used the MIME(Multipurpose Internet Mail Extension) which is HTTP response and performed "text/html;charset=ISO-8859-1".

Example

	<html>  
    <body>  
    <%@ 

page contentType=application/msword 

%>  
    Today is: <%= new java.util.Date() %>  
    </body>  
    </html>

extends

It is performed the parent class for inherited by servlet.

info

It is sets the information of the JSP page when it is inherite by perform with getServletInfo() method of Servlet interface.

Example

    <html>  
    <body>    
    <%@ 

page info="composed by Sonoo Jaiswal" %>  
    Today is: <%= new java.util.Date() %>  
    </body>  
    </html>

In web container can be create method getServletInfo() for resulting servlet.

Example

 public String 

getServletInfo() {  
      return "composed by Sonoo 

Jaiswal";   
    }

buffer

It makes sets the buffer size(kilobytes) which is handle output by the JSP page and default buffer size is 8Kb.

Example

	<html>  
    <body> 
    <%@ 

page buffer="16kb" %>  
    Today is: <%= new java.util.Date() %>  
    </body>  
    </html>

language

It is specified of the scripting language.

isELIgnored

In this attribute to be ignore the Expression Language (EL) in jsp by the isELIgnored attribute. By default its value is false i.e. Expression Language is enabled by default. We see Expression Language later.

<%@ page isELIgnored="true" %>//Now EL 

will be ignored

In this attribute is performed Servlet and JSP both are multithreaded and you want to control this behaviour of JSP page, you can use isThreadSafe attribute of page directive.

In isThreadSafe value is true then you make it false, the web container will serialize the multiple requests.

<%@ page isThreadSafe="false" %>

The web container in such a case, will generate the servlet as:

 public class SimplePage_jsp extends HttpJspBase   
      implements SingleThreadModel{  
    .......  
    }

errorPage

The errorPage attribute is used to define the error page, if exception occurs in the current page, it will be redirected to the error page.

Example of errorPage attribute

    //index.jsp  
    <html>  
    <body>   
    <%@ 

page errorPage="myerrorpage.jsp" %>  
     <%= 

100/0 

%>  
    </body>  
    </html>

isErrorPage

The isErrorPage attribute is used to declare that the current page is the error page. Note: The exception object can only be used in the error page.

Example of isErrorPage attribute

	//myerrorpage.jsp  
    <html>  
    <body>  
    <%@ 

page isErrorPage="true" %>  
     Sorry an exception occured!<br/>  
    The exception is: <%= exception %>   


    </body>  
    </html>