Input Validation Without a Bean
Before we look
at
the two remaining database sections, let’s go back and take a
look at the two application pages we skipped earlier, namely the
enter.jsp
and validate.jsp
pages used for input to the employee registration.
In Chapter 5, I introduced you to validation of
user input using an application-specific bean. The bean contains all
validation code and provides an isValid( )
method that can be used in a JSP page to decide how to proceed. This
is the approach I recommend, but if you’re developing a
JSP-based application and there isn’t a Java programmer around,
there’s another way to do the validation. I’ll describe
this alternative here.
The validate.jsp
page uses the
StringFormat
utility class to validate the input
format without a bean. If an input parameter is not valid, an error
message is saved in a Vector
object and the
request is forwarded back to the enter.jsp
page.
The enter.jsp
page loops through all error
messages in the Vector
and adds them to the
response, so to the user, the result is identical to that of the
bean-based validation approach you saw in Chapter 5.
Let’s look at validate.jsp
first, shown in
Example 9.6.
Example 9-6. Validation Without Application Beans (validate.jsp)
<%@ page language="java" %> <%@ page import="com.ora.jsp.util.*" %> <jsp:useBean id="errorMessages" scope="request" class="java.util.Vector" /> <% if (request.getParameter("userName").length( ) == 0) { errorMessages.addElement("User Name missing"); } if ...
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