1. 2 Day + Java Developer's Guide
  2. Create Login and Logout Functionality

9 Create Login and Logout Functionality

The HR Web Application has two users, namely hradmin and hrstaff.

Once you login to the HR Application, you see the landing page, with details of the web application. The hradmin and hrstaff have different privileges and access to different features.

A login page to enter the username and password.

This chapter shows the required classes and additional code required to build the Login and Logout functionality in the application.

  • Create a XML file tomcat-users.xml for login functionality.

  • Create a HTML page login.html to login the user.

  • Create a HTML page login-failed.html to display the error message.

  • Create a web.xml to authenticate the users during login.

  • Create a HTML page about.html to show more details about the application.

  • Create a landing page index.html and define the html pages for redirection.

  • Add code to the servlet WebController.java to process logout.

9.1 Create tomcat-users.xml

Create an XML file tomcat-users.xml and list down the users you want to allow access to. Specify both the username and password for each one of the users.

Class Name: /java/HRWebApp/tomcat-users.java

Github Location: tomcat-users.xml

Steps to create the xml file:

  1. Create the file tomcat-users.xml. 
    <?xml version='1.0' encoding='utf-8'?> z
<tomcat-users xmlns="http://tomcat.apache.org/xml"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd" version="1.0">
<role rolename="manager"/>
<role rolename="staff"/>
<user username="hradmin" password="welcome" roles="manager,staff"/>
<user username="hrstaff" password="welcome" roles="staff"/>
</tomcat-users>
  2. Place this file under TOMCAT_HOME/conf/tomcat-users.xml on your machine.

9.2 Create login.html

The login page is displayed when you invoke the main page of the web application. The login page displays the fields to capture the username and password.

Class Name: src/main/webapp/login.html

Github Location: login.html

Steps to create the HTML page:

  1. Create the title, head, and stylesheet for login.html.
    <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Login to Jdbc Web Sample application</title>
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<style>
#cent {
    position:absolute;
    top:50%;
    left:50%;
    margin-top:-50px; /* this is half the height of your div*/
    margin-left:-100px; /*this is half of width of your div*/
  }
   td {
     height: 30px;
   }

</style>
</head>
  2. Create the <body> and <form> to submit the login credentials entered by the user.
    <body>
<div id="cent">
<form method="POST" action="j_security_check">
<table>
<tr>
<td colspan="2">Login to the Jdbc Web Sample application:</td>
</tr>
<td>Name:</td>
<td><input type="text" name="j_username" /></td>
</tr>
<tr>
<td>Password:</td>
<td><input type="password" name="j_password"/></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="Go" /></td>
</tr>
</table>
</form>
</div>
</body>

9.3 Create login-failed.html

A html page to display the error messgae if the login is unsuccessful.

Class Name: src/main/webapp/login-failed.html

Github Location: login-failed.html

Steps to create the HTML page:

  1. Create the login-failed.html as shown below.
    <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Login Failed</title>
</head>
<body>
<p>
Sorry, login failed!
</p>
</body>
</html>

9.4 Create web.xml

The web.xml file consists of descriptors to authenticate the users when the login page is displayed to the user.

Class Name: src/main/webapp/WEB-INF/web.xml

Github Location: web.xml

Steps to create the xml file:

  1. Use the following code to create the web.xml file.
    <!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<display-name>Jdbc Web Sample</display-name>
<security-role>
<role-name>manager</role-name>
</security-role>
<security-role>
<role-name>staff</role-name>
</security-role>
<security-constraint>
<web-resource-collection>
<web-resource-name>Wildcard means whole app requires 
authentication</web-resource-name>
<url-pattern>/*</url-pattern>
<http-method>GET</http-method>
<http-method>POST</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>manager</role-name>
</auth-constraint>
<user-data-constraint>
<transport-guarantee>NONE</transport-guarantee>
</user-data-constraint>
</security-constraint>
<security-constraint>
<web-resource-collection>
<web-resource-name>Wildcard means whole app requires 
authentication</web-resource-name>
<url-pattern>/*</url-pattern>
<http-method>GET</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>staff</role-name>
</auth-constraint>
<user-data-constraint>
<transport-guarantee>NONE</transport-guarantee>
</user-data-constraint>
  </security-constraint>
<login-config>
<auth-method>FORM</auth-method>
<form-login-config>
<form-login-page>/login.html</form-login-page>
<form-error-page>/login-failed.html</form-error-page>
</form-login-config>
</login-config>
</web-app>

9.5 Create about.html

The about.html file displays information about the HR Application, users and functionalities.

Class Name: src/main/webapp/about.html

Github Location: about.html

Steps to use the HTML page: Download the about.html and use it in your application.

9.6 Create index.html

The index.html file consists of all details about the HR Web Application. It describes in detail its users and functionalities.

Class Name: src/main/webapp/index.html

Github Location: index.html

Steps to create the HTML page:

  1. Create the title, head, and stylesheet for index.html.
    <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Employee table listing</title>
<link rel="stylesheet" type="text/css" href="css/app.css" >
<style>
iframe:focus {
outline: none;
}
iframe[seamless] {
display: block;
}
</style>
</head>
<body>
  2. Create <body> and actions for the features through navigation links and logout.
    <body>
<div id="sideNav" class="sidenav">

<a href="javascript:void(0)" class="closebtn" onclick="closeNav()" class="staff">×</a>
<a href="javascript:switchSrc('listAll.html')" class="staff">List All</a>
<a href="javascript:switchSrc('listById.html')" class="staff">Search By Id</a>

<a href="javascript:switchSrc('listByName.html')" class="manager">Update Employee Record</a>
<a href="javascript:switchSrc('incrementSalary.html')" class="manager">Increment Salary</a>
<a href="javascript:switchSrc('about.html')">About</a>
</div>
<div id="main">
<div align="right">
<div
id="myrole"
        style="display:inline; color:#393318; display: block; background-color:#eff0f1;position: absolute; top: 20px; right: 8%;"
    >myrole</div>
<a href="javascript:void(0)"
       onclick="logout()"
       class="staff"
       style="display: block; position: absolute; top: 20px; right: 1%">Logout</a>
</div>
<div>
<span style="font-size:30px;cursor:pointer" onclick="openNav()"> Java 2 Days HR Web Application		</span>
</div>
<div>
<iframe id="content"
src="about.html"
frameborder="0"
style="overflow:hidden; height:100%; width:100%"
height="100%"
width="100%"></iframe>
</div>
</div>
<script>
function openNav() {
  document.getElementById("sideNav").style.width = "256px";
  document.getElementById("main").style.marginLeft = "256px";
}

function closeNav() {
  document.getElementById("sideNav").style.width = "0";
  document.getElementById("main").style.marginLeft= "0";
}

function switchSrc(src) {
  document.getElementById('content').src = src;
}

function logout() {

  var xmllogout = new XMLHttpRequest();
  xmllogout.open("GET", "WebController?logout=true", true, "_", "_");
  xmllogout.withCredentials = true;
  // Invlalid credentials to fake logout
  xmllogout.setRequestHeader("Authorization", "Basic 00001");
  xmllogout.send();

  xmllogout.onreadystatechange = function() {
    window.location.replace("index.html");
  }

 return true;
}

var xmlhttp = new XMLHttpRequest();
var url = "getrole";

xmlhttp.onreadystatechange = function() {
  if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
    role = xmlhttp.responseText;
    console.log("role: " +role);
    if (role == "staff") {
      console.log ("disabling manager");
      var x = document.getElementsByClassName('manager');
      for(i = 0; i < x.length; ++i) {
        x[i].style.display = 'none';
      }
    }
    document.getElementById('myrole').innerHTML = ' '+role+' ';
  }
}
xmlhttp.open("GET", url, true);
xmlhttp.send();
</script>
</body>

9.7 Add the code to a Servlet to process the request

Add the relevant code to WebController.java to login and logout of the application.

Class Name: src/main/java/com/oracle/jdbc/samples/web/WebController.java

Github Location: WebController.java

Steps to add the code:

  1. Open the WebController.java class. To create the WebController.java, refer to Creating a Servlet to Process the Request. Use the same class and add the required code.
  2. Declare a variable LOGOUT to capture the status of the user. This is a global variable, hence, declare it outside the method processRequest() but within the WebController class.
    private static final String LOGOUT = "logout";
  3. The method processRequest() is already created in the ListAll feature. Now, we add the code to implement Logout functionality. Create an if block to verify the functionality you will invoke based on input. Check if the input value is LOGOUT.
    if ((value = request.getParameter(LOGOUT)) != null) {
/* Getting session and then invalidating it */

    HttpSession session = request.getSession(false);
   if (request.isRequestedSessionIdValid() && session != null)   {
        session.invalidate();
   }
handleLogOutResponse(request,response);
   response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
return;
}
  4. If the input value is LOGOUT, invoke the method to handle the logout of user.
    
private void handleLogOutResponse(HttpServletRequest request,
HttpServletResponse response) {
    Cookie[] cookies = request.getCookies();
    for (Cookie cookie : cookies) {
      cookie.setMaxAge(0);
      cookie.setValue(null);
      cookie.setPath("/");
      response.addCookie(cookie);
    }
  }