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>