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A simple JSF facelets taglib example 

Fang
Joined:
08/13/2009
Posts:
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November 03, 2011 19:47:38    Last update: November 08, 2011 20:24:47
This is a step-by-step example to create a really simple facelet taglib (in JSF 2 with Maven).
  1. Create a simple Maven project with: 
    mvn archetype:create -DgroupId=com.example -DartifactId=facelet-tag

    Three files are created as a result:
    • pom.xml
    • src/main/java/com/example/App.java
    • src/test/java/com/example/AppTest.java

    This project should be able to build with: 
    mvn package

  2. Add facelet API dependencies to pom.xml: 
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.example</groupId>
  <artifactId>facelet-tag</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>facelet-tag</name>
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
	<groupId>org.apache.myfaces.core</groupId>
	<artifactId>myfaces-api</artifactId>
	<version>2.1.3</version>
	<scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
	    <version>2.3.2</version>
            <configuration>
               <source>1.6</source>
               <target>1.6</target>
            </configuration>
         </plugin>
    </plugins>
  </build>
</project>

    The compiler plugin section is optional.

  3. Remove src/main/java/com/example/App.java, create a new Java class as the facelet Tag Handler (HelloTagHandler.java): 
    package com.example;

import java.io.IOException;

import javax.faces.component.UIComponent;
import javax.faces.component.UIComponentBase;
import javax.faces.context.FacesContext;
import javax.faces.context.ResponseWriter;
import javax.faces.view.facelets.FaceletContext;
import javax.faces.view.facelets.TagAttribute;
import javax.faces.view.facelets.TagHandler;
import javax.faces.view.facelets.TagConfig;

/**
 * Custom facelet tag that says hello.
 *
 */
public class HelloTagHandler extends TagHandler {
    private String name = "Anonymous";

    public HelloTagHandler(TagConfig config) {
	super(config);
	TagAttribute a = getAttribute("name");
	if (a != null) {
	    name = a.getValue();
	}
    }

    public void apply(FaceletContext context, UIComponent parent) 
		throws IOException {
	UIComponentBase c = new UIComponentBase() {
	    public void encodeEnd(FacesContext ctx) throws IOException {
		ResponseWriter w = ctx.getResponseWriter();
		w.write(String.format(
		    "<p>Hello %s! I am FaceletTag.</p>",
		    name
		));
	    }

	    // abstract method in base, must override
	    public String getFamily() {
		return "com.example.facelettag.test";
	    }
	};
	parent.getChildren().add(c);
    }
}

    This tag handler simply prints a "Hello" message.

  4. Create facelet tag declaration file src/main/resources/META-INF/hello.taglib.xml: 
    <?xml version="1.0" encoding="UTF-8"?>
<facelet-taglib
    xmlns="http://java.sun.com/xml/ns/javaee"
    version="2.0">
    <namespace>http://www.example.com/ns/facelettags</namespace>
    <tag>
	<tag-name>hello</tag-name>
	<handler-class>com.example.HelloTagHandler</handler-class>
    </tag>
</facelet-taglib>

  5. Build the JAR with 
    mvn clean package

  6. Optionally, install it to the local repository: 
    mvn install



To use the taglib, simply drop the jar file into WEB-INF/lib inside the WAR. This is a test page: 
<!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:my="http://www.example.com/ns/facelettags">
<h:head>
	<title>Facelet Tag Test</title>
</h:head>

<h:body>
    <h1>Facelet Tag Test</h1>
    <my:hello name="Jack"/>
</h:body>
</html>
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