Cookies in java
HTTP protocol is a stateless.This mean that every HTTP request is different fro others. Sometimes it is necessary to keep track of the sequence of related request sent by by a client to perform some task this process is called session tracking . Cookies are one of the technique of the session tracking.
A Cookie is a [key value] form of key-value pair created by the server and is installed in the client browser when the client ,makes a request for the first time.A browser is also maintains the list of cookies install in it and send it to the server as a part of subsequent HTTP request.
A cookie is represented by using the javax.servlet.http.Cookie class and created using the following constructor.
Cookies(String key, String value) .
A cookie is added by the help of addCookie() method of the HttpServletResponse class. . Similarly , server can get all the cookies sent by the browser by using getCookies() method of HttpServletRequest class. There are two types of cookies are available. Non-persistent cookie and persistent cookies. A non persistent cookie valid for a single session and it removes each time the user close the browser . A persistent cookies however is valid for multiple sessions and it is removed when the user close the browser. A cookie is defined as a small piece of information.
Example:In this example we will transfer data from one file to another file using cookies in Servlets in java.
Components:
1. cookie.html
2 First servlet.java
3. Second servlet.java
1.Cookie.html File:
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form method="get" action="./FirstServlet">
UserName:<input type="text" name="uname"><br><br>
Password:<input type="password" name="upwd"><br><br>
<input type="submit" value="submit">
</form>
</body>
</html>
2. FirstServlet.java File:
package com.coo;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FirstServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public FirstServlet() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws Exception {
response.getWriter().append("Served at: ").append(request.getContextPath());
response.setContentType("text/html");
try
{
PrintWriter pw=response.getWriter();
pw.println("<br>");
String uname= request.getParameter("uname");
String upwd= request.getParameter("upwd");
pw.println("userName:"+ uname);
pw.println("<br>");
Cookie ck1=new Cookie("user1",uname);
Cookie ck2=new Cookie("user2",upwd);
pw.println("password:"+ upwd);
response.addCookie(ck1);
response.addCookie(ck2);
pw.println("<form action='./SecondServlet' method='get'>");
pw.println("<input type='submit' value='submit'>");
pw.println("</form>");
pw.close();
}
catch(IOException e)
{
}
}
}
3.SecondServlet.java File:
package com.dj;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SecondServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public SecondServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws Exception {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
try {
response.setContentType("text/html");
PrintWriter pw=response.getWriter();
Cookie ck[]=request.getCookies();
pw.println("userName:"+ ck[0].getValue());
Cookie ck1[]=request.getCookies();
pw.println("<br>");
pw.println("password:"+ck[1].getValue());
pw.close();
}
catch (Exception e) {
}
}
}
Output:
When we enter the data in the FirstServlet.java file then it will transfer the data into Second Servlet.java' file by using cookies.
