Java Examples in a Nutshell, 3rd Edition

ListManager Views

The View classes used by the ListManager application are JSP pages. Although the Controller class can handle four actions (login, edit, unsubscribe, and logout) the web application requires only two views, login.jsp and edit.jsp, which are shown in Examples Example 20-10 and Example 20-11.

login.jsp displays a login form, obviously. As part of the form, it displays an optional message, specified by the Controller servlet with the HttpServletRequest.setAttribute( ) method. This message explains errors (“Incorrect Password”) or provides confirmation (“logged out”). The login form has input fields for an email address and password, and has buttons to log in and edit an existing subscription or to subscribe a new address to the list. Whichever button the user clicks, the email address and password are sent to the “login.action” URL, which is handled by the login( ) method of the Controller servlet.

The edit.jsp page includes a form that allows the user to edit his mail preferences; this form POSTs to the “edit.action” URL, which is handled by the edit( ) method of the Controller. It also includes buttons that POST to the “logout.action” and “unsubscribe.action” URLs, which are handled by the logout( ) and unsubscribe( ) methods of the Controller.

Note that both login.jsp and edit.jsp clearly document their inputs and outputs. This helps integrate these View objects with the action methods of the Controller servlet. This technique is particularly helpful for large web ...