Java Web Programming [8/9] : JSF and AJAX

Module 8:
JSF and AJAX Basics

Thanisa Kruawaisayawan
Thanachart Numnonda
www.imcinstitute.com

Objectives
 What is JSF?
 Real-Life Examples of AJAX Apps
 What is AJAX and Why AJAX?
 Technologies Used In AJAX
 XMLHttpRequest

2

JavaServer™ Faces (JSF) Framework
Is…
A server side user interface (UI)
component framework for Java™
technology-based web
applications. (Validators)

Drag-and-drop UI components to
build a web Application.

Application Configuration File

 XML file for configuring resources required at
application startup time
 navigation rules, converters, validators, render kits
 Usually named as faces-config.xml
 A <faces-config> tag must enclose all of the other
declarations
<faces-config>
....
</faces-config>

Two Tag Libraries

 jsf_core
 Definesother JSF related tags
 Independent of any rendering technology

 html_basic
 Defines tags for representing common HTML user
interface components
 JSP page need to declare them
<%@ taglib uri="http://java.sun.com/jsf/core/" prefix="f" %>
<%@ taglib uri="http://java.sun.com/jsf/html/" prefix="h" %>

<f:view> element
 Represents UIViewRoot component
 All component tags on the page must be
enclosed in the view tag
<f:view>
... other faces tags, possibly mixed with other
content ...
</f:view>
 Optional locale attribute
 Overrides the Locale stored in the UIViewRoot

HTML Tags

 Used to control display data or accept data
from the user
 Common attributes
 id:uniquely identifies the component
 value: identifies an external data source mapped
to the component's value
 binding: identifies a bean property mapped to
the component instance

Built-in UI Component Classes
 UIForm:
 Encapsulates a group of controls that submit
data to the application. This component is
analogous to the form tag in HTML.
 UIInput:
 Takes data input from a user
 is a subclass of UIOutput
 UIOutput:
 Displays data output on a page

UIForm & <h:form> tag
 UIForm UI component
 An input form with child components
representing data that is either presented to the
user or submitted with the form
 Encloses all of the controls that display or
collect data from the user
 Include HTML markup to layout the controls
on the page
 <h:form> tag itself does not perform any layout

UIInput & UIOutput Components

 UIInput component displays a value to a user and
allows the user to modify this data
 The most common example is a text field
 UIOutput component displays data that cannot be
modified
 The most common example is a label
 Conversions can occur
 Both UIInput and UIOutput components can be
rendered in several different ways

UICommand & <h:commandButton>

 UICommand component performs an action
when it is activated
 Most common renderers are Button and Link

UICommand & <h:commandButton>

 Additional attributes
 action:
 is either a logical outcome String or a JSF EL
expression that points to a bean method that returns a
logical outcome String
 In either case, the logical outcome String is used by

the navigation system to determine what page to
access when the UICommand component is
activated

Example1: <h:commandButton> from
carDetail.jsp
<h:commandButton action="#{carstore.buyCurrentCar}"
value="#{bundle.buy}" />
 action attribute

 references a method on the CarStore backing bean that
performs some processing and returns an outcome
 outcome is passed to the default NavigationHandler, which
matches the outcome against a set of navigation rules defined
in the application configuration file.
 value attribute
 references the localized message for the button's label
 bundle part of the expression refers to the ResourceBundle
that contains a set of localized messages

greeting.jsp
<f:view>
<h:form id="helloForm" >
<h2>Hi. My name is Duke. I'm thinking of a number from
<h:outputText value="#{UserNumberBean.minimum}"/> to
<h:outputText value="#{UserNumberBean.maximum}"/>. Can you guess it?
</h2>

<h:graphic_image id="waveImg" url="/wave.med.gif" />
<h:inputText id="userNo" value="#{UserNumberBean.userNumber}“ />
<h:commandButton id="submit" action="success" value="Submit" />
<p>
<h:messages style="color: red; font-family: 'New Century Schoolbook', serif;
font-style: oblique; text-decoration: overline" id="errors1" for="userNo"/>
</h:form>
</f:view>
</HTML>

Validation Model
 jsf-core tag library also defines a set of tags that
correspond to the standard Validator
implementations
 Most of the tags have a set of attributes for
configuring the validator's properties
 minimum and maximum

Validator Tags

 <f:validator>
 Registers a custom Validator on a component
 <f:validateLength>
 Registers a LengthValidator on a component
 <f:validateLongRange>
 Registers a LongRangeValidator on a component
 <f:validateDoubleRange>
 Registers a DoubleRangeValidator on a component

Real-Life Examples of AJAX Apps
 Google maps
 http://maps.google.com/
 Google Suggest
 http://www.google.com/webhp?complete=1&hl=en
 Gmail
 http://gmail.com/
 Yahoo Maps (new)
 http://maps.yahoo.com/
 Many more are popping everywhere
17

What is AJAX?
 Asynchronous JavaScript And XML
 DHTML plus Asynchronous communication
capability through XMLHttpRequest
 Pros
 Most viable RIA technology so far
 Tremendous industry momentum
 Several toolkits and frameworks are emerging
 No need to download code & no plug-in required

 Cons
 Still
browser incompatibility
 JavaScript is hard to maintain and debug 18

Why AJAX?
 Intuitive and natural user interaction
 Noclicking required
 Mouse movement is a sufficient event trigger
 "Partial screen update" replaces the "click, wait, and
refresh" user interaction model
 Only user interface elements that contain new information
are updated (fast response)
 The rest of the user interface remains displayed without
interruption (no loss of operational context)
 Asynchronous communication replaces "synchronous
request/response model."
19

Interrupted user
operation while
the data is being
fetched

Uninterrupted
user operation
while data is
being fetched

20

Server-Side AJAX Request Processing
 Server programming model remains the same
 It
receives standard HTTP GETs/POSTs
 Can use Servlet, JSP, JSF, ...
 With minor constraints
 More frequent and finer-grained requests from
client
 Response content type can be
 text/xml
 text/plain

 text/json

 text/javascript 22

Demo Scenario

 Runsample AJAX applications within
NetBeans IDE
 Auto completion
 Data validation
 Progress bar
 You can try this demo yourself
 These applications are provided as built-in sample
applications in NetBeans
23

Data Validation Example

24

Steps of AJAX Operation
1. A clientevent occurs
2. An XMLHttpRequest object is created
3. The XMLHttpRequest object is configured
4. The XMLHttpRequest object makes an async.
request
5. The ValidateServlet returns an XML document
containing the result
6. The XMLHttpRequest object calls the callback()
function and processes the result
7. The HTML DOM is updated
25

1. A Client event occurs
 A JavaScript function is called as the result of
an event
 Example: validateUserId() JavaScript function
is mapped as a event handler to a onkeyup
event on input form field whose id is set to
“userid”
<input type="text" size="20" id="userid" name="id"
onkeyup="validateUserId();">

26

2. An XMLHttpRequest object is created
var req;
function initRequest() {
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
} else if (window.ActiveXObject) {
isIE = true;
req = new ActiveXObject("Microsoft.XMLHTTP");
}
}
function validateUserId() {
initRequest();
req.onreadystatechange = processRequest;
if (!target) target = document.getElementById("userid");
var url = "validate?id=" + escape(target.value);
req.open("GET", url, true);
req.send(null);
} 27

3. An XMLHttpRequest object is
configured with a callback function
var req;
isIE = true;
}
}
initRequest();
req.onreadystatechange = processRequest; // callback function
req.send(null); 28
}

4. XMLHttpRequest object makes an async.
request
isIE = true;
}
}
initRequest();
req.onreadystatechange = processRequest;
req.send(null);
}
 URL is set to validate?id=greg
29

5. The ValidateServlet returns an XML
document containing the results (Server)

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {

String targetId = request.getParameter("id");

if ((targetId != null) && !accounts.containsKey(targetId.trim())) {
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.getWriter().write("<valid>true</valid>");
} else {
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.getWriter().write("<valid>false</valid>");
}
} 30

6. XMLHttpRequest object calls callback()
function and processes the result
 The XMLHttpRequest object was configured to
call the processRequest() function when there is
a state change to the readyState of the
XMLHttpRequest object

function processRequest() {
if (req.readyState == 4) {
if (req.status == 200) {
var message = ...;
31

7. The HTML DOM is updated
 JavaScript technology gets a reference to any element
in a page using DOM API
 The recommended way to gain a reference to an
element is to call
 document.getElementById("userIdMessage"), where
"userIdMessage" is the ID attribute of an element appearing
in the HTML document
 JavaScript technology may now be used to modify the
element's attributes; modify the element's style
properties; or add, remove, or modify child elements
32

1. <script type="text/javascript">
2. function setMessageUsingDOM(message) {
3. var userMessageElement = document.getElementById("userIdMessage");
4. var messageText;
5. if (message == "false") {
6. userMessageElement.style.color = "red";
7. messageText = "Invalid User Id";
8. } else {
9. userMessageElement.style.color = "green";
10. messageText = "Valid User Id";
11. }
12. var messageBody = document.createTextNode(messageText);
13. // if the messageBody element has been created simple replace it otherwise
14. // append the new element
15. if (userMessageElement.childNodes[0]) {
16. userMessageElement.replaceChild(messageBody,
17. userMessageElement.childNodes[0]);
18. } else {
19. userMessageElement.appendChild(messageBody);
20. }
21. }
22. </script>
23. <body>
24. <div id="userIdMessage"></div>
25. </body> 33

Acknowledgement
Most contents are borrowed from the
presentation slides of Sang Shin, Java™
Technology Evangelist, Sun Microsystems,
Inc.

34

Thank you

thananum@gmail.com
www.facebook.com/imcinstitute
www.imcinstitute.com

35

Java Web Programming [8/9] : JSF and AJAX

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