Cookies In Servlet In Java | Session And Cookies In Java Servlet | Cookies In Servlet In Java In Hindi

Cookies in Servlet

A cookie is a small piece of information that is persisted between the multiple client requests.

A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number.

Fig: Cookies In Servlet 

How Cookie works

By default, each request is considered as a new request. In cookies technique, we add cookie with response from the servlet. So cookie is stored in the cache of the browser. After that if request is sent by the user, cookie is added with request by default. Thus, we recognize the user as the old user.

Types of Cookie

There are 2 types of cookies in servlets.

1.    Non-persistent cookie

2.    Persistent cookie

 

Non-persistent cookie

It is valid for single session only. It is removed each time when user closes the browser.

Persistent cookie

It is valid for multiple session . It is not removed each time when user closes the browser. It is removed only if user logout or signout.

Advantage of Cookies

1.    Simplest technique of maintaining the state.

2.    Cookies are maintained at client side.

Disadvantage of Cookies

1.    It will not work if cookie is disabled from the browser.

2.    Only textual information can be set in Cookie object.

How to create Cookie?

 The simple code to create cookie.

    Cookie ck=new Cookie("user","sonoo jaiswal");//creating cookie object  

     response.addCookie(ck);//adding cookie in the response  

How to delete Cookie?

The simple code to delete cookie. It is mainly used to logout or signout the user.

   Cookie ck=new Cookie("user","");//deleting value of cookie  

   ck.setMaxAge(0);//changing the maximum age to 0 seconds  

   response.addCookie(ck);//adding cookie in the response  

How to get Cookies?

The simple code to get all the cookies.

Cookie ck[]=request.getCookies();  

for(int i=0;i<ck.length;i++){  

out.print("<br>"+ck[i].getName()+" "+ck[i].getValue());//printing name and value of cookie  

}  

Example of Servlet Cookies

In this example, we are storing the name of the user in the cookie object and accessing it in another servlet. As we know well that session corresponds to the particular user. So if you access it from too many browsers with different values, you will get the different value.

index.html

     <form action="servlet1" method="post">  

     Name:<input type="text" name="userName"/><br/>  

     <input type="submit" value="go"/>  

     </form>  

FirstServlet.java 

      import java.io.*;  

      import javax.servlet.*;  

      import javax.servlet.http.*;  

     public class FirstServlet extends HttpServlet {  

  public void doPost(HttpServletRequest request, HttpServletResponse res ponse){  

    try{  

  

    response.setContentType("text/html");  

    PrintWriter out = response.getWriter();  

          

    String n=request.getParameter("userName");  

    out.print("Welcome "+n);  

  

    Cookie ck=new Cookie("uname",n);//creating cookie object  

    response.addCookie(ck);//adding cookie in the response  

  

    //creating submit button  

    out.print("<form action='servlet2'>");  

    out.print("<input type='submit' value='go'>");  

    out.print("</form>");  

          

    out.close();  

  

        }catch(Exception e){System.out.println(e);}  

  }  

     }  

 

SecondServlet.java

    import java.io.*;  

    import javax.servlet.*;  

    import javax.servlet.http.*;  

  

   public class SecondServlet extends HttpServlet {  

  

   public void doPost(HttpServletRequest request, HttpServletResponse response){  

    try{  

  

    response.setContentType("text/html");  

    PrintWriter out = response.getWriter();  

      

    Cookie ck[]=request.getCookies();  

    out.print("Hello "+ck[0].getValue());  

  

    out.close();  

  

         }catch(Exception e){System.out.println(e);}  

    }   

}  

web.xml

  <web-app>  

  

    <servlet>  

   <servlet-name>s1</servlet-name>  

    <servlet-class>FirstServlet</servlet-class>  

     </servlet>  

     <servlet-mapping>  

    <servlet-name>s1</servlet-name>   

    <url-pattern>/servlet1</url-pattern>  

     </servlet-mapping>  

     <servlet>  

   <servlet-name>s2</servlet-name>  

   <servlet-class>SecondServlet</servlet-class>  

   </servlet>  

   <servlet-mapping>  

   <servlet-name>s2</servlet-name>  

   <url-pattern>/servlet2</url-pattern>  

    </servlet-mapping>  

   </web-app>