Directive Tags in JSP:
Directive tags are used to give directions used
by the JSP translator during the translation stage of the JSP life cycle.Directive
tag allows the user to import packages, define error handling pages or session
information of JSP page. These tags are used to set global values such as class
declarations, methods to be implemented, output content type and so on. Thus we
can say that the
directive
tag provides additional information to
the JSP Engine regarding the jsp page.
Types of Directive
Tags:
According to the JSP
specification, there are mainly three directive tags are available:
- page
- include
- taglib
The Page Directive
Tag: The page directive tag holds the instruction used by the translator
during the translator stage of the JSP life cycle. You can use the
directive tags multiple times in a JSP page. The page directive used in any part
of the JSP page. Thus we can say that, page directive
sets page-level preferences for the JSP. Here is the syntax for the page
directive:
<%@page attributes%>
E.g.: <%@page
language="java" %>
Attributes for it
is:
<%@ page language="java"
extends="classA"
import="classP{,+}"
session="true|false"
buffer="none|sizeInKB"
autoFlush="true|false"
isThreadSafe="true|false"
info="text"
errorPage="jspUrl"
isErrorPage="true|false"
contentType="mimeType{;charset=charset}"
%>
The Include
Directive: The include directive tag is used to merge the contents of two or
more files during the translation stage of the JSP lifecycle. It also allows the
developer to include other JSP or static page when JSP is translated into a
Servlet, while the action <jsp:include> includes the resources at request time.
The syntax for the include directive:
<%@include file= "file path"%>
E.g.: <%@include
file="/portal/login.jsp"%>
The Taglib directive: The taglib
directive tag is used to declare a custom tag library in a JSP page so that the
tags related to that custom tag library can be used in the same JSP page. The
taglib directive enables you to create your own custom tags. The syntax for it
is:
<%@taglib uri="URI"prefix="unique_prefix " %>
E.g.: <taglib>
<taglib-uri> http://www.sbi.com/Tags </taglib-uri>
<taglib-location> /sbibank/account/</taglib-location>
<taglib>
An Application of these Directive tags:
There is an example in which I will try to describe the application of
directive tag:
Login.jsp:
<html>
<body bgcolor="cyan">
<pre>
<form action="loginprocess.jsp">
<b>User Name</b> : <input type="text" name="uname"/>
<b>word</b> : <input type="text" name=""/>
<input type="submit" value="Login"/>
</form>
</pre>
</body>
</html>
Loginprocess.jsp:
<%@page import="java.sql.*"
errorPage="myerror.jsp" %>
<html>
<body bgcolor="pink">
<%
Connection con=null;
String uname=request.getParameter("uname");
String =request.getParameter("");
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:directive");
Statement st=con.createStatement();
ResultSet rs=st.executeQuery("select * from userdetails");
while(rs.next()){
%>
User Details For uname:<%=request.getParameter("uname")%>are not valid<br/>Try
again
<%@include file="/login.jsp"%>
<%
return;
}}
finally{
try{con.close();}
catch(Exception e){}
}
%>
This is a home Page<br>
welcome<%=uname%>
</body></html>
Error.jsp:
<%@page isErrorPage="true" %>
<html>
<body>
An exception is raised during request:<br/>
<b>
Exception: </b><br/>
 : : : : : :<%=exception.getMessage()%>
</b></br>
</body>
</html>
OUTPUT:
Login.jsp:
![login.gif]()
LoginProcess.jsp:
a. loginSuccess:
![loginprocess.gif]()
b. loginInvalid:
![Loginprocessinvalid.gif]()