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JSF - Ajax

2016-02-16 08:21 519 查看

Ajax: A Brief Introduction

AJAX stands for Asynchronous JavaScript And Xml.

Ajax is a technique to use HTTPXMLObject of JavaScript to send data to server and receive data from server asynchronously.

So using Ajax technique, javascript code exchanges data with server, updates parts of web page without reloading the whole page.

JSF provides execellent support for making ajax call. It provides f:ajax tag to handle ajax calls.

JSF Tag

<f:ajax execute="input-component-name" render="output-component-name" />

Tag Attributes

S.N.	Attribute & Description
1	disabled If true, the Ajax behavior will be applied to any parent or child components. If false, the Ajax behavior will be disabled.
2	event The event that will invoke Ajax requests, for example "click", "change", "blur", "keypress", etc.
3	execute A space-separated List of IDs for components that should be included in the Ajax request.
4	immediate If "true" behavior events generated from this behavior are broadcast during Apply Request Values phase. Otherwise, the events will be broadcast during Invoke Applications phase
5	listener An EL expression for a method in a backing bean to be called during the Ajax request.
6	onerror The name of a JavaScript callback function that will be invoked if there is an error during the Ajax request
7	onevent The name of a JavaScript callback function that will be invoked to handle UI events.
8	render A space-separated list of IDs for components that will be updated after an Ajax request.

Example Application

Let us create a test JSF application to test the custom component 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	Modify UserData.java file as explained below.
3	Modify home.xhtml as explained below. Keep rest of the files unchanged.
4	Compile and run the application to make sure business logic is working as per the requirements.
5	Finally, build the application in the form of war file and deploy it in Apache Tomcat Webserver.
6	Launch your web application using appropriate URL as explained below in the last step.

UserData.java

package com.tutorialspoint.test;

import java.io.Serializable;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;

@ManagedBean(name = "userData", eager = true)
@SessionScoped
public class UserData implements Serializable {

private static final long serialVersionUID = 1L;

private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

public String getWelcomeMessage(){
return "Hello " + name;
}
}

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:f="http://java.sun.com/jsf/core"
xmlns:tp="http://java.sun.com/jsf/composite/tutorialspoint">
<h:head>
<title>JSF tutorial</title>
</h:head>
<h:body>
<h2>Ajax Example</h2>
<h:form>
<h:inputText id="inputName" value="#{userData.name}"></h:inputText>
<h:commandButton value="Show Message">
<f:ajax execute="inputName" render="outputMessage" />
</h:commandButton>
<h2><h:outputText id="outputMessage"
value="#{userData.welcomeMessage !=null ?
userData.welcomeMessage : ''}"
/></h2>
</h:form>
</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 following result:

Enter name and press Show Message button. You will see the following result without page refresh/form submit.

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