<%
if request("infoid")<>"" then
set rs=conn.execute("select * from nproduct where id="&request("infoid"))
if not (rs.eof and rs.bof) then
proname=rs("proname")
content=rs("proinfo")
end if
rs.close
set rs=nothing
end if
%>
<%-- Include directive --%> <%@ include file="header.html" %>
Quizzes Index
JSP Professional, Chapter 12 Quiz Answers
by Dan Malks
<%-- Page directive that applies to entire page. --%> <%@ page language="java" %>
<%-- Identifies bean as "worker" and tells the page where to locate the bean. --%>
<%-- Set bean properties with a wildcard. --%>
<%-- Scoring --%>
<%-- Variable declaration in code scriptlet -->
<% int score = 0; %>
1.
<%-- The method getOne() was set up in the bean with the id "worker" --%> <%-- All Java code is enclosed in <% %>, leaving HTML to be easily --%> <%-- changed or updated. --%>
When large amounts of Java scriptlet code are mixed with HTML markup within a JSP page, not only do readability and reuse suffer, but often bugs are introduced as web-production team members, who may not be familiar with Java programming, need to modify the accompanying markup. Additionally, dependencies now exist among various teams competing for the same file, making the development process less efficient.
Doing an HTTP redirect requires a round-trip to the client. If this is not required, and the only desire is to forward the request to another resource, then this can be much more efficiently accomplished with the RequestDispatcher. Additionally, when using the dispatcher the state of the request object is maintained between resources, which will not be the case with the HTTP redirect.
Business logic is better contained in a JavaBeanTM or a servlet, which is owned by a software developer. When lots of Java code is embedded directly within the JSP page as scriptlets, the "cut-and-paste" mentality tends to prevail when it comes to code reuse.
Since the servlet is the initial contact point for each request, it is well-suited to handle logic that is common across multiple requests. A good example of this type of logic is an authentication check.
Using a business delegate reduces coupling between the presentation and business tiers. The presentation tier has no knowledge of the EJB implementation details, such as Java Naming and Directory InterfaceTM lookup.
Using Java scriptlets is the accepted method of doing iteration in JSPTM 1.0. In JSPTM 1.1, a custom tag may be used, which will hide the implementation details of the iteration code.
The term Page-Centric is used to describe an architecture where the initial contact point for the request is a JSP page. An example is shown visually below:
When the forward method is used, the invoking resource does not regain control. Multiple include invocations can be made from the same resource, while the invoking resource maintains execution control.
Error pages are invoked when there is an uncaught exception from within a particular page. In this case, we mention that the validationGaurd() method might throw an exception. If this exception is not caught within the page, then we vector control to the errorPage, as stipulated in the attribute of the given page directive.
This quiz used the Page-View with Bean Approach, detailed in HREF="/developer/Books/javaserverpages/">Chapter 12, JSP Archeticure. The first page of the quiz consists of regular HTML with a form that calls HREF="answer.txt">answer.jsp. Answer.jsp requests parameters from the bean, in this case, called QuizResponses. The page-view with bean approach for this quiz required extra work to write the bean, and it could have been done using the page-view approach without a bean, requesting invocation directly from the answer.jsp page. Deciding which approach is preferrable depends on the application and how much HTML and Java scriptlets need to be used. For this quiz we opted for the page-view with bean approach for illustration purposes.
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