Learn Java for Web Development

108 CHAPTER 3: Best Practices in Java EE Web Development

Listing 3-2 shows the fragment of a servlet that uses attributes.

   Line 3: This retrieves the userName from the request.

   Line 4: This sets the userName as an attribute in the request.

   Line 5: This retrieves the RequestDispatcher from the request.

   Line 6: This forwards to the view, passing request and response object. Note

that this request object has an attribute set in it for the userName. The view can

now make use of this attribute

Listing 3-3. The First JSP

1. Hello
2.<%= request.getAttribute("name") %>
3.
4.
5.
6.<% User u = (User) request.getAttribute("user"); %>
7.User is: <%= u.getName() %>
8.
9.

The separation of the view from the business logic depends on the attributes, as illustrated in
Listing 3-2 and Listing 3-3. JSP, in this manner, solved the problem of presentation cross-cutting
business logic in servlets. But as you can see in Listing 3-4, with the scriptlets (Java code) intermingled
in the presentation code (JSP), now the business logic cross-cuts the presentation concern.

Listing 3-4. Using a Scriptlet and an Expression in JSP

1.<% User u = new User(); %>
2.User is: <%= u.getName() %>

   Line 1: The scriptlet creates an instance of a class called User.

   Line 2: This outputs the user name using Expression.

What went wrong? Scriptlets and expressions brought Java code into JSP. Prior to JSP, the
presentation code cross-cut the business code. With JSP, the business code cross-cuts the
presentation code. So JSP, inadvertently, didn’t actually solve anything but turned the problem of
cross-cutting the business and presentation logic upside down. The scriptlet and expression in
Listing 3-4 could indeed be easily replaced by JSP standard actions (), as shown in Listing 3-5.

Listing 3-5. Using JSP Standard Action sand Expression Language

1.
2.User is: ${user.name}

Listing 3-5 does the same thing that Listing 3-4 does but without using any Java code inside the
JSP page.