Patterns: Implementing Self-Service in an SOA Environment

Chapter 9. JSF front-end scenario 259

In the case of the ITSOMart application, we define the CustomerDO class as the

managed bean responsible for storing session data. The class stores the basic

customer data carried through multiple screens in the application.

9.3.3 JSF input validation

The JSF framework provides a variety of ways of validating user input. This

section discusses some of these options, and describes the ones employed in

the ITSOMart application. Implementation details for the various validation

options are presented later in 9.4.6, “Implementing input validation” on page 280.

Client side versus server side validation

Before looking into the various JSF validation options, we first discuss one of

known limitations. JSF currently does not support client side validation. That

means that even the most simple of input format checking requires validation to

be performed on the server. This goes against the common practice for

Web-based applications, where simple input validation is often done on the client

side, using JavaScript.

The options in this case, are to stick with standard JSF validation, or manually

program client side validation with JavaScript. The JSF-based validation will fit in

naturally with the tooling and the framework, but the JavaScript client side

validation reduces the server load. Either option is valid, and the choice will

depend on the relative importance of reducing server load for the application in

question.

In the ITSOMart front-end, we have chosen to use JSF-based validation to

demonstrate this technique. Note that the specifications for the upcoming JSF2.0

release will include client-side validation, which should remedy the current

shortcoming.

Standard component validation

Most JSF UI components include at least some level of input validation. These

include checks for required values, string length, and date formats. These are not

comprehensive, but they do offer some useful basic functionality. The ITSOMart

front-end makes use of all appropriate standard validation provided by the JSF

components.

Custom validation

The validation provided in the standard JSF components is limited to basic data

types such as strings, numbers, and dates. Clearly this is not sufficient for most

complex applications. However, JSF does provide a simple framework for

specifying custom-defined validation functions. Once a special validation class is