Programming Tutorials

Tag libraries

By: aathishankaran in JSP Tutorials on 2007-02-13  

JSP 1.1 introduces a method of extending JSP tags, called "tag libraries".  These libraries allow addition of tags similar to jsp:include or jsp:forward, but with different prefixes other than jsp: and with additional features.

Each tag-library will have its own tag-library specific documentation.  In order to use the tag library, you use the "taglib" directive to specify where your tag library's "description" resides.  For the tag library, the (recommended) directive is as follows

<%@ taglib prefix="blx" uri="/blx.tld" %>

 The "uri" specifies where to find the tag library description.
The "prefix" is unique for the tag library.  
This directive is saying that we will be using the tags in this library by starting them with blx

The tag library provides a blx:getProperty tag.  This tag can be used to allow the user to edit form data.  In our GetName.jsp file, we will now add a jsp:useBean and place the form inside blx:getProperty.

 The GetName.jsp is

<%@ taglib prefix="blx" uri="/blx.tld" %>
<jsp:useBean id="user" class="user.UserData" scope="session"/>
<blx:getProperty name="user" property="*">
What's your name? <INPUT TYPE=TEXT NAME=username SIZE=20><BR>
What's your e-mail address? <INPUT TYPE=TEXT NAME=email SIZE=20><BR>
What's your age? <INPUT TYPE=TEXT NAME=age SIZE=4>

Note that the blx:getProperty doesn't end with /> but is instead terminated by a separate </blx:getProperty> line.  This puts all the form input fields inside the blx:getProperty so they can be appropriately modified by the tag library.

Try putting a link to GetName.jsp from the NextPage.jsp, and you will see that the bean's data shows up automatically in the input fields.

The user can now edit the data.

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