Java Server Faces

JSFDone by: Esraa M Yaseen

Submitted to: Eng. Abdelnasser

Abdelhadi

MVC

Because it provides a flexible solution to these problems by decoupling the Model, View, and Controller components of an application while providing a uniform interface between them.

Motivation

Motivation

MVC …

Web application framework

A web application framework (WAF) is a software framework that is designed to support the

development of dynamic websites, web applications, web services and web resources. The

framework aims to alleviate the overhead associated with common activities performed in web

development. For example, many frameworks provide libraries for database access, templating frameworks and session management, and they often promote code reuse.  For a comparison of

concrete web application frameworks

Motivation

Make a decision!

If: You wish to provide different representations of the same applicationdata (for example, a table versus a graph). You wish to provide different looks and feels (perhaps for differentoperating systems) for your user interface without affecting the rest ofyour application. User-driven events must immediately update application data or otheruser interface components, while changes to application data must bereflected immediately in user interface components. You wish to reuse one or more user interface components indepen-dently of application data.

Then … Use JSF

JSF Main features

 JSF has the following main features: JSF is based on the Model-View-Controller concept JSF has a stateful UI component model, e.g. each

component is aware of its data JSF separates the functionality of a component from the

display of the component. The renderer is responsible of displaying the component for a certain client. This renderer can get exchanged. The standard renderer for JSF components is the HTML renderer.

JSF support listeners on UI components JSF support data validation, data binding and data

conversion between the UI and the model

The greatest advantage that JavaServer Faces technology has over Struts is its flexible, extensible UI component model, which includes:

A standard component API for specifying the state and behavior of a wide range of components, including simple components, such as input fields, and more complex components, such as scrollable data tables. Developers can also create their own components based on these APIs, and many third parties have already done so and have made their component libraries publicly available.

A separate rendering model that defines how to render the components in various ways. For example, a component used for selecting an item from a list can be rendered as a menu or a set of radio buttons.

An event and listener model that defines how to handle events generated by activating a component, such as what to do when a user clicks a button.

Conversion and validation models for converting and validating component data.

 Prerequisites to use JSF

To use JSF you need: JSF Implementation (in the form of the JSF

jars) The JSTL tags library A Java runtime environment A web-container to use JSF in (for example

Tomcat)

Requirements Installation  EclipseFor JSP development you need the Eclipse WTP and an installed Tomcat.  JSF libraryA JSF library is required. We will later use Eclipse to download and install the Apache MyFaces JSF implementation during project creation. JSLT library

The Genius of JSF1* A component model allows you to reuse components that come from a third party withouthaving to learn a new component model (the model is standard). 2* components fit into a part/whole hierarchy and can be composed into more complex components. The component-based model is beneficial to the handling of the user action.3* A user action, such as a button click, flows through a well-defined process from the button click to the business logic that performs the requested process.JSF provides well-defined points for your code to plug into the flow and be executed. 4* The component-based model also allows developers to focus on providing great features instead of trying to focus on two or three different models for building Web-based user interfaces. It also allows the promise of reusable off-the-shelf components in the future.

JSF configuration files OverviewJSF is based on the following configuration files: web.xml - General web application configuration file faces-config.xml - Contains the configuration of the JSF application.  web.xml*JSF requires the central configuration list web.xml in the directory WEB-INF of the application. This is similar to other web-applications which are based on servlets.*You must specify in web.xml that a "FacesServlet" is responsible for handling JSF applications. "FacesServlet" is the central controller for the JSF application. "FacesServlet" receives all requests for the JSF application and initializes the JSF components before the JSP is displayed.

 faces-config.xml"faces-config.xml" allows to configure the application, managed beans, convertors, validators, and navigation.

What typical JSF application consists of?

A typical JSF application consists of the following parts:

JavaBeans components for managing application state and behavior.

Event-driven development (via listeners as in traditional GUI development).

Pages that represent MVC-style views; pages reference view roots via the JSF component tree.

Controller

The JSF controller consists primarily of a Front Controller servlet called FacesServlet, one or more configuration files, and a set of action handlers The FacesServlet is responsible for receiving incoming requests from Web clients and then performing a logical set of steps for preparing and dispatching a response.

JSF Request-Processing Life Cycle.

Example

NotesThe first thing you’ll notice here i: Our action handler here is simply a method in a

JavaBean that has no parameters and returns a String. We chose to

place this method in our LoginBean. In more complex applications, action handlers may be

organized differently. A JSF action handler returns a logical result (success

or failure in this case), while a Struts Action uses the logical result to actually

return what page should be forwarded to next.

Example .. configuration file As part of the request-processing life cycle,

the next component tree (or JSP page in this example) will be determined by

the logical result returned by this action handler. As with Struts, JSF allows you

to define a configuration file. Among other things, this configuration file

provides a mechanism for defining user interface workflow. An example of what

the workflow for our example might look like is provided next...

configuration file

Model This distinction between the View and

Model layers of a Web application. becomes more difficult in JSF.

must resist the temptation to let JSF component data objects influence your real Model (business objects)

Failing to do so often results in high coupling between the View and Model layers

What is Managed Bean? JavaBean objects managed by a JSF

implementation are called managed beans. A managed bean describes how a bean is created and managed.

Declaring a Model object as a managed bean

Once declared in this manner, each managed bean and its declared properties can be referenced and bound to user interface components

View As you have probably figured out by now, the View

layer in JSF consists primarily of the component tree. One benefit of JSF is that individual components or the whole component tree can be rendered differently to support multiple client user interface types. In most cases, you will be dealing with a markup language such as HTML that is used in a JSP. Depending on the client device type,

components could render themselves in the markup language appropriate for that device.

View … What is view object?   A view object is a model object used

specifically in the presentation tier. It contains the data that must display in the view layer and the logic to validate user input, handle events, and interact with the business-logic tier. The backing bean is the view object in a JSF-based application. Backing bean and view object are interchangeable terms.

In this case, we can bind the input fields to properties on our LoginBean JavaBean.

Note You could have made use of Converters,

Validators, and even custom Renderers as part of the user interface. In fact, a Converter and Validator component would be useful even in this simple example. These components are very useful for delegating and reusing common user interface tasks. In the interest of simplicity, we decided not to use these special JSF components in our little

login example.

Composite Components

The primary component is usually a form, frame, or page. Within these root components, other components are arranged hierarchically to achieve the desired interface.

Composite Components• AbstractComponent. This participant

defines an interface common to allcomponents. It implements this common interface to provide defaultbehavior, a portion of which is used for accessing and managing nestedcomponents.• SimpleComponent. This participant

represents and defines the behaviorof primitive components.• CompositeComponent. This participant

represents and defines thebehavior of container components. It provides a mechanism for storingand managing nested components by implementing those portions of• the AbstractComponent interface.Client. This participant accesses and manipulates component hierarchiesthrough the AbstractComponent interface.

Composite Components When a Client performs an

operation on a component, a uniform response is provided regardless of the underlying structure. If the component is a SimpleComponent, the operation is performed directly. Otherwise, we have a

CompositeComponent that asks each nested component to perform the requested operation. The CompositeComponent may perform additional operations before responding to the Client. In either case, these interactionsare hidden beneath a common interface.

JSF Events

JSF provides two kinds of events: A Value Changed event

(javax.faces.event.ValueChangeEvent) is useful for observing node or changing the text in a text field).

An Action event (javax.faces.event.ActionEvent ) is useful for observing the activation of a user inter-face component that is a descendent of UICommand (this includes buttons and

hyperlinks). Both of these event types ultimately descend from a

commonancestor in JSF (javax.faces.event.FacesEvent).

JSF Events

There are essentially two steps to capturing events in JSF. The first step is to implement the appropriate listener interface

on the component you wish to receive an event. When implementing the ValueChangeListener interface, you’ll need to add a processValueChanged(...) method where you will implement the code that responds to the event. Similarly, when implementing

the ActionListener interface, you’ll need to add a processAction(...)method. When an event is dispatched to your listener component, these methods will be called by the JSF implementation. The second step to capturing an event in JSF is to register your

newly created listener.

Examples of JSF event handling

<h:inputText id=”userId” value=”#{login.userId}”><f:valueChangeListener type=”logindemo.UserLoginChanged” /></h:inputText><h:commandButton id=”login” commandName=”login”><f:actionListener type=”logindemo.LoginActionListener” /></h:commandButton>

You may be wondering if it is possible to combine some aspects of Strutswith JSF ?

component framework with existing Struts-based applications. The creators of Struts have created an integration library called Struts-Faces that is available on the Struts project Web site that does just that.

Summary

References John Wiley and Sons - Mastering Java Server Faces http://www.vogella.com/articles/JavaServerFaces/

article.html http://www.developersbook.com/jsf/interview-

questions/jsf-interview-questions-faqs.php http://help.eclipse.org/galileo/index.jsp?topic=/

org.eclipse.jst.jsf.doc.user/html/tasks/create_jsf_app.html

http://myfaces.apache.org/jsfintro.html http://www.mkyong.com/jsf2/jsf-2-0-hello-world-

example/ http://www.coderanch.com/t/212078/JSF/java/JSF