The Java EE 6 Tutorial, Volume I

Creating the Login Form and the Error Page

When using form-based login mechanisms, you must specify a page that contains the form you want to use to obtain the user name and password, as well as which page to display if login authentication fails. This section discusses the login form and the error page used in this example. The section Specifying Security in the Deployment Descriptor shows how you specify these pages in the deployment descriptor.

The login page can be an HTML page, a JSP page, or a servlet, and it must return an HTML page containing a form that conforms to specific naming conventions (see the Java Servlet 3.0 specification for more information on these requirements). To do this, include the elements that accept user name and password information between <form></form> tags in your login page. The content of an HTML page, JSP page, or servlet for a login page should be coded as follows:

<form method=post action="j_security_check" >
    <input type="text"  name= "j_username" >
    <input type="password"  name= "j_password" >

The full code for the login page used in this example can be found at tut-install/examples/web/hello2_formauth/web/loginform.html. An example of the running login form page is shown later in Figure 25–8. Here is the code for this page:

    <title>Login Page</title>

<h2>Hello, please log in:</h2>
<form action="j_security_check" method=post>
    <p><strong>Please Enter Your User Name: </strong>
    <input type="text" name="j_username" size="25">
    <p><p><strong>Please Enter Your Password: </strong>
    <input type="password" size="15" name="j_password">
    <input type="submit" value="Submit">
    <input type="reset" value="Reset">

The login error page is displayed if the user enters a user name and password combination that is not authorized to access the protected URI. For this example, the login error page can be found at tut-install/examples/web/hello2_formauth/web/loginerror.html. For this example, the login error page explains the reason for receiving the error page and provides a link that will allow the user to try again. Here is the code for this page:

    <title>Login Error</title>
    <c:url var="url" value="/index.jsp"/>
    <h2>Invalid user name or password.</h2>

    <p>Please enter a user name or password that is authorized to access this 
    application. For this application, this means a user that has been created in the 
    <code>file</code> realm and has been assigned to the <em>group</em> of 
    <code>TutorialUser</code>.  Click here to <a href="${url}">Try Again</a></p>