November 2005
Intermediate to advanced
896 pages
31h 5m
English
Content preview from Java Enterprise in a Nutshell, Third Edition
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Validation
Most software requires some kind of data entry, and in order to be user-friendly, an application should support the user as much as possible throughout the data entry process. This means identifying invalid input and giving the user a chance to fix it sooner rather than later.
JSF, as you might expect, has built-in support for validation . All JSF user interface components support validation through both built-in and custom validation rules.
Let’s take a look at the Add Books form (Figure 5-4) in the JSF Library, which needs to enforce minimum field lengths and mandatory fields. The Add Books function is available to librarians who have logged into the system. It allows them to fill out a simple form to create a new book.
Adding Validators to Forms
Example 5-8
shows the JSP source for the Add Books form. We’re using three
different kinds of validation: required fields, built-in validators,
and a custom validator (which we’ll see in more detail in the next
section). We’re also using the <h:message> tag to display
validation messages for each component.
Figure 5-4. Add Books form
Example 5-8. /view/addbook.jsp
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <html> <f:view> <head> <title>Add Book to Library</title> <link rel="stylesheet" type="text/css" href='<%= request.getContextPath() + "/css/app.css" %>'> ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.