BodyTagSupport Example
Example to illustrate the use of BodyTagSupport in a JSP page
BodyTagSupport class implements the BodyTag interface and you
can add additional functionalities in it to set property of bodyContent.
If you want to add other functionalities in this tag then there are some methods
which you have to override. Some important methods of this class are as
follows:
- doAfterBody() -After the body evaluation it does not
reevaluate and continue with the page
- doStartTag() - default working of start tag returns EVAL_BODY_BUFFERED
- doEndTag() - default working of end tag returns EVAL_PAGE
- getBodyContent() - it gets current bodyContent
This example will illustrate you how to make custom tags in JSP along with
implementation of BodyTagSupport's methods. To make custom tags in JSP
and to use them, we have made an application which have <tbl:stag>
</tbl:stag> tag which is being used to convert all contents of body of
the tag to
Upper case. For example, if it is written like this in JSP page
<tbl:stag>
hello ! i am Amit Kumar Raghuwanshi
</tbl:stag> |
So when JSP page would be executed then this tag will convert the body
content "hello ! i am Amit Kumar Raghuwanshi" to the following source
code in HTML like this:
<body>
HELLO ! I AM AMIT KUMAR RAGHUWANSHI
</body>
|
To implement these functionalities we have created following files:
- MyTag.java
- BodyTagExample.jsp
- stag.tld
MyTag.java is a simple java file which is extending BodyTagSupport
class. In this file we have overridden only one method of BodyTagSupport, doAfterBody(), which is firstly taking the bodyContent to a string
named "body" and then bodycontent.getEnclosingWriter() is
returning object of JspWriter type and these contents are to be converted
in UpperCase and then it will be displayed on the browser. This method doAfterBody()
is returning SKIP_BODY means that after the body evaluation :do not
reevaluate and continue with the page. Full code of this MyTag.java is
given as below :
1. MyTag.java
package stag;
import javax.servlet.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.util.*;
import java.io.*;
public class MyTag extends BodyTagSupport
{
public int doAfterBody() throws JspException {
try {
BodyContent bodycontent = getBodyContent();
String body = bodycontent.getString();
JspWriter out = bodycontent.getEnclosingWriter();
if(body != null) {
out.print(body.toUpperCase());
}
} catch(IOException ioe) {
throw new JspException("Error:"+ioe.getMessage());
}
return SKIP_BODY;
}
}
|
Another very important file is stag.tld which is playing very
important role in this example. This "stag.tld" is an XML file
which is setting the shortname, name, bodycontent ,tagclass
of this tag. Using these parameters setting in this tld file we are going
to make use of it in our JSP page in the following manner:
| <%@ taglib uri="/WEB-INF/stag.tld" prefix="tbl" %> |
Code for stag.tld is as following :
2. stag.tld
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag
Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>tbl</shortname>
<tag>
<name>stag</name>
<tagclass>stag.MyTag</tagclass>
<bodycontent>JSP</bodycontent>
<info>To Convert in Upper case tag</info>
</tag>
</taglib> |
JSP page "BodyTagExample.jsp" full code is here:
3. BodyTagExample.jsp
<%@ page language="java" %>
<%@ taglib uri="/WEB-INF/stag.tld" prefix="tbl" %>
<html>
<body>
<tbl:stag>
hello ! i am Amit Kumar Raghuwanshi
</tbl:stag>
</body>
</html> |
To run this example you have to follow these few steps :
- Create file MyTag.java and save it.
- Compile and put this MyTag.class file into WEB-INF/classes folder.
- Create and save stag.tld into WEB-INF folder.
- Create and save BodyTagExample.jsp file.
- Start and run tomcat server and type the following URL into address bar of
your browser
http://localhost:8080/vin/BodyTagExample.jsp
Output:
This is showing all body content in Upper Case letter as we have done
in our tag functionality. The HTML source code generated would be like this:
Any content which is not in <tbl:stag> will remain as it is. For
example
<%@ page language="java" %>
<%@ taglib uri="/WEB-INF/stag.tld" prefix="tbl" %>
<html>
<body>
<tbl:stag>
hello ! i am Amit Kumar Raghuwanshi
</tbl:stag>
<br>
This will remain as it is ...
</body>
</html> |
and its output would be like this:
Download Source Code
|
Del.icio.us
Digg
Google
Spurl
Blink
Furl
Simpy
Y! MyWeb
