JSF - Custom Tag

Quiz

JSF provides the developer with a powerful capability to define own custom tags, which can be used to render custom contents.

Defining a custom tag in JSF is a three-step process.

Step	Description
1a	Create a xhtml file and define contents in it using ui:composition tag
1b	Create a tag library descriptor (.taglib.xml file) and declares the above custom tag in it.
1c	Register the tag libray descriptor in web.xml

Step 1a: Define custom tag contents : buttonPanel.xhtml

<h:body>
   <ui:composition> 
      <h:commandButton type = "submit" value = "#{okLabel}" />
      <h:commandButton type = "reset" value = "#{cancelLabel}" /> 
   </ui:composition>
</h:body>

Step 1b: Define a tag library : tutorialspoint.taglib.xml

As the name mentions a Tag library is a library of tags. Following table describes important attributes of a tag library.

S.No	Node & Description
1	facelet-taglib Contains all the tags.
2	namespace Namespace of the tag library and should be unique.
3	tag Contains a single tag
4	tag-name Name of the tag
5	source Tag implementation

<facelet-taglib>
   <namespace>http://tutorialspoint.com/facelets</namespace>
   <tag>
      <tag-name>buttonPanel</tag-name>
      <source>com/tutorialspoint/buttonPanel.xhtml</source>
   </tag>
</facelet-taglib>

Step 1c: Register the tag library :web.xml

<context-param>
   <param-name>javax.faces.FACELETS_LIBRARIES</param-name>
   <param-value>/WEB-INF/tutorialspoint.taglib.xml</param-value>
</context-param>

Using a custom tag in JSF is a two-step process.

Step	Description
2a	Create a xhtml file and use custom tag library's namespace
2b	Use the custom tag as normal JSF tags

Step 2a: Use Custom Namespace: home.xhtml

<html xmlns = "http://www.w3.org/1999/xhtml"   
   xmlns:h = "http://java.sun.com/jsf/html"
   xmlns:ui = "http://java.sun.com/jsf/facelets">
   xmlns:tp = "http://tutorialspoint.com/facelets">

Step 2b: Use Custom Tag: home.xhtml

<h:body>
   <tp:buttonPanel okLabel = "Ok" cancelLabel = "Cancel" /> 		
</h:body>

Example Application

Let us create a test JSF application to test the template tags in JSF.

Step	Description
1	Create a project with a name helloworld under a package com.tutorialspoint.test as explained in the JSF - First Application chapter.
2	Create com folder under WEB-INF directory.
3	Create tutorialspoint folder under WEB-INF > com directory.
4	Create buttonPanel.xhtml file under WEB-INF > com > tutorialspoint folder. Modify it as explained below.
5	Create tutorialspoint.taglib.xml file under WEB-INF folder. Modify it as explained below.
6	Modify web.xml file under WEB-INF folder as explained below.
7	Modify home.xhtml as explained below. Keep rest of the files unchanged.
8	Compile and run the application to make sure business logic is working as per the requirements.
9	Finally, build the application in the form of war file and deploy it in Apache Tomcat Webserver.
10	Launch your web application using appropriate URL as explained below in the last step.

buttonPanel.xhtml

<?xml version = "1.0" encoding = "UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns = "http://www.w3.org/1999/xhtml"   
   xmlns:h = "http://java.sun.com/jsf/html"
   xmlns:ui = "http://java.sun.com/jsf/facelets">
   
   <h:body>
      <ui:composition> 
         <h:commandButton type = "submit" value = "#{okLabel}" />
         <h:commandButton type = "reset" value = "#{cancelLabel}" /> 
      </ui:composition>
   </h:body>
</html>

tutorialspoint.taglib.xml

<?xml version = "1.0"?>
<!DOCTYPE facelet-taglib PUBLIC
"-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN"
"http://java.sun.com/dtd/facelet-taglib_1_0.dtd">

<facelet-taglib>
   <namespace>http://tutorialspoint.com/facelets</namespace>
   
   <tag>
      <tag-name>buttonPanel</tag-name>
      <source>com/tutorialspoint/buttonPanel.xhtml</source>
   </tag>
</facelet-taglib>

web.xml

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
   <display-name>Archetype Created Web Application</display-name>
   <context-param>
      <param-name>javax.faces.PROJECT_STAGE</param-name>
      <param-value>Development</param-value>
   </context-param>	
   
   <context-param>
      <param-name>javax.faces.FACELETS_LIBRARIES</param-name>
      <param-value>/WEB-INF/tutorialspoint.taglib.xml</param-value>
   </context-param>
   
   <servlet>
      <servlet-name>Faces Servlet</servlet-name>
      <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
   </servlet>
   
   <servlet-mapping>
      <servlet-name>Faces Servlet</servlet-name>
      <url-pattern>*.jsf</url-pattern>
   </servlet-mapping>
</web-app>

home.xhtml

<?xml version = "1.0" encoding = "UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns = "http://www.w3.org/1999/xhtml"   
   xmlns:h = "http://java.sun.com/jsf/html"
   xmlns:ui = "http://java.sun.com/jsf/facelets"
   xmlns:tp = "http://tutorialspoint.com/facelets">
   
   <h:head>
      <title>JSF tutorial</title>			
   </h:head>
   
   <h:body>
      <h1>Custom Tags Example</h1>
      <tp:buttonPanel okLabel = "Ok" cancelLabel = "Cancel" />
   </h:body>
</html>

Once you are ready with all the changes done, let us compile and run the application as we did in JSF - First Application chapter. If everything is fine with your application, this will produce the following result.

jsf_facelets_tags.htm

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