HttpSession:
HttpSession is an interface that provides a way to identify a user in multiple page requests. A unique session ID is given to the user when the first request comes. This ID is stored in a request parameter or in a cookie.
How to get a session object?
HttpServletRequest interface’s getSession() method is used to get the session object.
Syntax:
HttpSession session = request.getSession();
How to set attributes in the session objects?
HttpSession interface’s setAttribute() method is used to set attributes in the session object.
Syntax:
public void setAttribute(String name,Object value);
Example:
session.setAttribute("attName", "attValue");
How to get an attribute from the session object?
HttpSession interface’s getAttribute() method is used to get attributes from the session object.
Syntax:
public Object getAttribute(String name);
Example:
String value = (String) session.getAttribute("attName");
Session management example using HttpSession:
LoginServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* This class is used to set values in session.
* @author W3schools360
*/
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
//no-argument constructor
public LoginServlet() {
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
//get parameters from request object.
String userName = request.getParameter("userName").trim();
String password = request.getParameter("password").trim();
//check for null and empty values.
if(userName == null || userName.equals("") ||
password == null || password.equals("")){
out.print("Please enter both username " +
"and password. <br><br>");
RequestDispatcher requestDispatcher =
request.getRequestDispatcher("/login.html");
requestDispatcher.include(request, response);
}//Check for valid username and password.
else if(userName.equals("jai") && password.equals("1234")){
HttpSession session=request.getSession();
session.setAttribute("userName",userName);
session.setAttribute("password",password);
out.println("Logged in successfully.<br>");
out.println("Click on the below link to see " +
"the values of Username and Password.<br>");
out.println("<a href="DisplaySessionValueServlet">" +
"Click here</a>");
out.close();
}else{
out.print("Wrong username or password. <br><br>");
RequestDispatcher requestDispatcher =
request.getRequestDispatcher("/login.html");
requestDispatcher.include(request, response);
}
}
}
DisplaySessionValueServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* This class is used to get values from session.
* @author W3schools360
*/
public class DisplaySessionValueServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
//no-argument constructor
public DisplaySessionValueServlet() {
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
//get parameters from session object.
HttpSession session=request.getSession(false);
String userName =(String)session.getAttribute("userName");
String password =(String)session.getAttribute("password");
out.println("Username: " + userName + "");
out.println("Password: " + password);
out.close();
}
}
login.html
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login</title>
<form action="LoginServlet" method="post">
Username:<input type="text" name="userName">
<br><br>
Password:<input type="password" name="password">
<br><br>
<input type="submit" value="login">
</form>
web.xml
<!--?xml version="1.0" encoding="UTF-8"?-->
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>
com.w3schools.business.LoginServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>DisplaySessionValueServlet</servlet-name>
<servlet-class>
com.w3schools.business.DisplaySessionValueServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DisplaySessionValueServlet</servlet-name>
<url-pattern>/DisplaySessionValueServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>login.html</welcome-file>
</welcome-file-list>
</web-app>
