PARTIII PART PART in Java

Encode QR Code in Java PARTIII PART PART

<form-bean name="loginbean" type="orgapachestrutsactionDynaActionForm"> <form-property name="userid" type="javalangString"/> <form-property name="password" type="javalangString"/> </form-bean>

Once it is defined, you can access the field values in your application, as shown here:

String userid = (string)((DynaActionForm)form)get("userid");

This is very similar to what you can do with JSF; however, with Struts you don t have the ability to bind the field properties directly to properties of Java classes and have their values synchronized automatically upon form submissions

As shown in Figure 3-1, the JSF request processing lifecycle s ability to automatically synchronize server-side Java Bean properties to a hierarchical set of components that are based on the UI presented to the client user is a major advantage over other Web technologies This capability is known as state management and is a cornerstone of the value provided by JSF

UIViewRoot HtmlOutputBody HtmlForm HtmlInputText HtmlMessage HtmlInputText HtmlMessage HtmlSelectOneRadio UISelectItem UISelectItem HtmlMessage HtmlInputText HtmlMessage HtmlSelectOneMenu UISelectItem UISelectItem UISelectItem HtmlMessage HtmlCommandButton HtmlOutputHead

FIGURE 3-1

Part I:

A brief aside about the evolution of Web applications will set the stage for a better understanding of state management in JSF The success of the Web as a platform for software is due mainly to its simplicity and versatility The user sits in front of a piece of software that understands a standard, lightweight syntax for describing a user interface (HTML) Information encoded with this syntax is delivered to the user-agent with a standard lightweight network protocol (HTTP) The user-agent responds to user actions and initiates further HTTP requests to the server as necessary, and the cycle continues For the Web to reach as wide an audience as possible, both HTML and HTTP needed to be as simple as possible, but no simpler, and certainly needed to be open standards One key ingredient in this successful recipe is the statelessness of HTTP Stateless means that one transaction between a client and server has no memory of the previous transaction Unfortunately, this can be a problem for sophisticated Web applications that require a persistent state JavaServer Faces solves this problem by automatically maintaining a serverside View that represents the important parts of the current state of the client This allows the JSF developer to focus on the server-side components, letting the request processing lifecycle, or plumbing, take care of the synchronization of the server-side View and what is presented in the client browser The often-tedious job of writing code to handle each individual request value or change in state of the UI is handled automatically by the JavaServer Faces request processing lifecycle through a set of phases during which specific tasks are performed to process the data in a consistent manner

state while also simplifying the task of writing UI Components that maintain state During the execution of the lifecycle, the JSF runtime will 1 Determine if this is a page request or a resource request If this is a resource request, it will serve the bytes of the resource to the user-agent Otherwise, it will load the Facelets or JSP page 2 Create a server-side representation of the UI 3 Produce markup suitable for rendering in the browser The JSF lifecycle automatically keeps track of the changed portions of the state, so the client-side view is always in step with the server-side view

The processing of incoming request data often requires different types of jobs, including: checking if the incoming data is valid, triggering server-side application logic to fulfill the request, and finally rendering the response to the client The JSF request processing lifecycle performs these tasks in a consistent order and is governed by a set of well-defined phases This approach allows each phase to clearly state the preconditions that exist before executing the phase, and the post conditions that exist after it is executed

JSF 20 TIP Follow-up requests for resources referenced in the page markup, such as images,

scripts, and style sheets, can be handled by JSF While this behavior does indeed happen as a part of the JSF lifecycle, it is not a part of the core page processing lifecycle and is best described in the context of the UIComponent system, in 7

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