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sâmbătă, 14 februarie 2015

JSF 2.2 - Writing a custom component handler skeleton

In order to write and configure a ComponentHandler, you have to accomplish several steps:

·         First, you need a component (built-in, or custom). Let's suppose that we have the below dummy component:

package custom.componenthandler;

import javax.faces.component.FacesComponent;
import javax.faces.component.UIComponentBase;

@FacesComponent(value=DummyComponent.COMPONENT_TYPE)
public class DummyComponent extends UIComponentBase {

 public static final String COMPONENT_FAMILY = "dummy.components";
 public static final String COMPONENT_TYPE = "dummy";

 @Override
 public String getFamily() {
  return COMPONENT_FAMILY;
 }
}

·         Further, extend the ComponentHandler class and override the desired methods. Per example, a dummy component handler skeleton is listed below - it simply delegates tasks to the superclass:

package custom.componenthandler;

import java.util.logging.Logger;
import javax.faces.component.UIComponent;
import javax.faces.view.facelets.ComponentConfig;
import javax.faces.view.facelets.ComponentHandler;
import javax.faces.view.facelets.FaceletContext;

public class CustomComponentHandler extends ComponentHandler {

 private static final Logger logger =
  Logger.getLogger(CustomComponentHandler.class.getName());

 public CustomComponentHandler(ComponentConfig config) {
  super(config);
 }

 //only in JSF 2.2
 @Override
 public UIComponent createComponent(FaceletContext ctx) {
  logger.info("Inside 'createComponent' method");
  return super.createComponent(ctx);
 }

 @Override
 public void onComponentCreated(FaceletContext ctx, UIComponent c, UIComponent parent) {
  logger.info("Inside 'onComponentCreated' method");
  super.onComponentCreated(ctx, c, parent);
 }

 @Override
 public void onComponentPopulated(FaceletContext ctx, UIComponent c, UIComponent parent) {
  logger.info("Inside 'onComponentPopulated' method");
  super.onComponentPopulated(ctx, c, parent);
 }
}

·         Next, you need to write a *.taglib.xml file to link the handler class with the component. Per example, dummy.taglib.xml from below:

<?xml version="1.0" encoding="UTF-8"?>
<facelet-taglib
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facelettaglibrary_2_0.xsd"
 version="2.0">

 <namespace>http://dummy.components.org/dummy</namespace>

 <tag>
  <tag-name>dummy</tag-name>
  <component>
   <component-type>dummy</component-type>
   <handler-class>custom.componenthandler.CustomComponentHandler</handler-class>
  </component>
       
  <attribute>
   <name>id</name>
   <type>java.lang.String</type>
   <description>Component id</description>
   <required>false</required>
  </attribute>
       
  <!-- ... -->     
 </tag>

</facelet-taglib>

·         Finally, configure the *taglib.xml file in web.xml file. Per example:
...
<context-param>
 <param-name>javax.faces.FACELETS_LIBRARIES</param-name>
 <param-value>/WEB-INF/tags/dummy.taglib.xml</param-value>
</context-param>
...

Done! The complete code is available on GitHub.

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