Week-8:
Date:
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AIM:
User Authentication:
Assume
four users user1, user2, user3 and user4 having the passwords pwd1, pwd2, pwd3
and pwd4 respectively. Write a servelet
for doing the following.
1. Create
a Cookie and add these four user id’s and passwords to this Cookie.
2. Read
the user id and passwords entered in the Login form (week1) and authenticate
with the values (user id and passwords) available in the cookies.
If he is a
valid user (i.e., user-name and password match) you should welcome him by name
(user-name) else you should display “You are not an authenticated user “. Use
init-parameters to do this. Store the user-names and passwords in the web.xml
and access them in the servlet by using the getInitParameters() method.
DESCRIPTION:
Servlet Life cycle:
1.
Servlet class loading
2.
Servlet Instantiation
3.
call the init method
4.
call the service method
5.
call destroy method
Class loading and instantiation
If you consider a servlet to be just like
any other Java program, except that it runs within a servlet container, there
has to be a process of loading the class and making it ready for requests.
Servlets do not have the exact equivalent of a main method that causes them to
start execution.
When a web container starts it searches for
the deployment descriptor (WEB.XML) for each of its web applications. When it
finds a servlet in the descriptor it will create an instance of the servlet
class. At this point the class is considered to be loaded (but not
initialized).
The init method
The HttpServlet class inherits the init
method from GenericServlet. The init method performs a role slightly similar to
a constructor in an “ordinary” Java program in that it allows initialization of
an instance at start up. It is called automatically by the servlet container
and as it causes the application context (WEB.XML) to be parsed and any
initialization will be performed. It comes in two versions, one with a zero
parameter constructor and one that takes a ServletConfig parameter.
The servlet engine creates a request object and a response object.
The servlet engine invokes the servlet service() method, passing the request
and response objects. Once the init method returns the servlet is said to be
placed into service. The process of using init to initialize servlets means
that it is possible to change configuration details by modifying the deployment
descriptor without having them hard coded in with your Java source and needing
a re-compilation.
void
init(ServletConfig sc)
Calling the service method
The service() method gets information about the request
from the request object, processes the request, and uses methods of the
response object to create the client response. The service method can invoke
other methods to process the request, such as doGet(), doPost(), or methods you
write. The service method is called for
each request processed and is not normally overridden by the programmer.
The code that makes a servlet “go” is the. servlet
void service(ServletRequest
req,ServletResponse res)
The destroy Method
Two typical reasons for the destroy method
being called are if the container is shutting down or if the container is low
on resources. This can happen when the container keeps a pool of instances of
servlets to ensure adequate performance. If no requests have come in for a
particular servlet for a while it may destroy it to ensure resources are
available for the servlets that are being requested. The destroy method is called only once,
before a servlet is unloaded and thus you cannot be certain when and if it is
called.
void destroy()
ServletConfig Class
ServletConfig object is used by the Servlet Container to pass information to the
Servlet during it's initialization. Servlet can obtain information regarding
initialization parameters and their values using different methods of ServletConfig class initialization parameters are name/value pairs used to
provide basic information to the Servlet during it's initialization like JDBC
driver name, path to database, username, password etc.
Methods of ServletConfig class
Following are the four methods of this class :
Following are the four methods of this class :
- getInitParameter(String
paramName) Returns value of the given
parameter. If value of parameter could not be found in web.xml file then a
nullvalue is returned. - getInitParameterNames() Returns an
Enumerationobject containing all the names of initialization parameters provided for this Servlet. - getServletContext() Returns reference to the
ServletContextobject for this Servlet. It is similar togetServletContext()method provided byHttpServletclass. - getServletName() Returns name of the Servlet as provided in the web.xml file or if none is provided then returns complete class path to the Servlet.
PROGRAM:
cologin.html:
<html>
<head>
<title> login Page </title>
<p style= "background:yellow;
top:100px; left:250px; position:absolute; ">
</head>
<body>
<form
ACTION="clogin">
<label> Login </label>
<input type="text"
name="usr" size="20"> <br> <br>
<label> Password </label>
<input type="password"
name="pwd" size="20"> <br> <br>
<input type="submit"
value="submit">
</form>
</body>
</html>
cologin1.html
<html>
<head>
<title> login Page </title>
<p style= "background:yellow;
top:100px; left:250px; position:absolute; ">
</head>
<body>
<form
ACTION="clogin1">
<label> Login </label>
<input type="text"
name="usr" size="20"> <br> <br>
<label> Password </label>
<input type="password"
name="pwd" size="20"> <br> <br>
<input type="submit"
value="submit">
</form>
</body>
</html>
Addcook.java:
import javax.servlet.* ;
import javax.servlet.http.*;
import java.io.*;
public class Addcook extends HttpServlet
{
String user,pas;
public void service(HttpServletRequest
req,HttpServletResponse res) throws ServletException,IOException
{
res.setContentType("text/html");
PrintWriter out=res.getWriter();
Cookie c1=new
Cookie("usr1","suni");
Cookie p1=new
Cookie("pwd1","ani");
Cookie c2=new
Cookie("usr2","abc");
Cookie p2=new
Cookie("pwd2","123");
Cookie c3=new
Cookie("usr3","def");
Cookie p3=new
Cookie("pwd3","456");
Cookie c4=new Cookie("usr4","mno");
Cookie p4=new
Cookie("pwd4","789");
res.addCookie(c1);
res.addCookie(p1);
res.addCookie(c2);
res.addCookie(p2);
res.addCookie(c3);
res.addCookie(p3);
res.addCookie(c4);
res.addCookie(p4);
out.println("COOKIE ADDED");
}
}
Clogin.java:
import javax.servlet.* ;
import javax.servlet.http.*;
import java.io.*;
public class Clogin extends HttpServlet
{
String user,pas;
public void service(HttpServletRequest
req,HttpServletResponse res) throws ServletException,IOException
{
res.setContentType("text/html");
PrintWriter out=res.getWriter();
user=req.getParameter("usr");
pas=req.getParameter("pwd");
Cookie[] c=req.getCookies();
for(int i=0;i<c.length;i++)
{
if((c[i].getName().equals("usr1")&&c[i+1].getName().equals("pwd1"))||
c[i].getName().equals("usr2") &&c[i+1].getName().equals("pwd2"))||(c[i].getName().equals("usr3")&&
c[i+1].getName().equals("pwd3"))||(c[i].getName().equals("usr4")&&
c[i+1].getName().equals("pwd4") ))
{
if((user.equals(c[i].getValue())
&& pas.equals(c[i+1].getValue())) )
{
//RequestDispatcher
rd=req.getRequestDispatcher("/cart.html");
rd.forward(req,res);
}
else
{
out.println("YOU
ARE NOT AUTHORISED USER ");
//res.sendRedirect("/cookdemo/cologin.html");
}
}
}
}
}
Web.xml:
<web-app>
<servlet>
<servlet-name>him</servlet-name>
<servlet-class>Clogin</servlet-class>
</servlet>
<servlet>
<servlet-name>him1</servlet-name>
<servlet-class>Addcook</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>him</servlet-name>
<url-pattern>/clogin</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>him1</servlet-name>
<url-pattern>/clogin1</url-pattern>
</servlet-mapping>
</web-app>
OUTPUT:
 |
| http://wikibrand.blogspot.in |
 |
| http://wikibrand.blogspot.in |
 |
| http://wikibrand.blogspot.in |
 |
| http://wikibrand.blogspot.in |
2. Read
the user id and passwords entered in the Login form (week1) and authenticate with the values (user id
and passwords) available in the cookies.
If he is a
valid user (i.e., user-name and password match) you should welcome him by name
(user-name) else you should display “You are not an authenticated user “.
Use
init-parameters to do this. Store the user-names and passwords in the
webinf.xml and access them in the servlet
by using the getInitParameters() method.
home.html:
<html>
<head>
<title>Authentication</title>
</head>
<body>
<form action="ex1">
<label>Username </label>
<input type="text"size="20"
name="user"><br><br>
password<input type="text" size="20"
name="pwd"><br><br>
<input type="submit" value="submit">
</form>
</body>
</html>
Example1.java
import javax.servlet.*;
import java.io.*;
public class Example1 extends GenericServlet
{
private String user1,pwd1,user2,pwd2,user3,pwd3,user4,pwd4,user5,pwd5;
public void init(ServletConfig
sc)
{
user1=sc.getInitParameter("username1");
pwd1=sc.getInitParameter("password1");
user2=sc.getInitParameter("username2");
pwd2=sc.getInitParameter("password2");
user3=sc.getInitParameter("username3");
pwd3=sc.getInitParameter("password3");
user4=sc.getInitParameter("username4");
pwd4=sc.getInitParameter("password4");
}
Public void
service(ServletRequest req,ServletResponse res)throws ServletException,IOException
{
res.setContentType("text/html");
PrintWriter
out=res.getWriter();
user5=req.getParameter("user");
pwd5=req.getParameter("pwd");
if((user5.equals(user1)&&pwd5.equals(pwd1))||(user5.equals(user2)&&pwd5.equals(pwd2))||(user5.equals(user3)&&pwd5.equals(pwd3))||(user5.equals(user4)&&pwd5.equals(pwd4)))
out.println("<p> welcome to"+user5.toUpperCase());
else
out.println("You are
not authorized user");
}
}
web.xml:
<web-app>
<servlet>
<servlet-name>Example</servlet-name>
<servlet-class>Example1</servlet-class>
<init-param>
<param-name>username1</param-name>
<param-value>pvpsit</param-value>
</init-param>
<init-param>
<param-name>password1</param-name>
<param-value>cse</param-value>
</init-param>
<init-param>
<param-name>username2</param-name>
<param-value>1234</param-value>
</init-param>
<init-param>
<param-name>password2</param-name>
<param-value>4567</param-value>
</init-param>
<init-param>
<param-name>username3</param-name>
<param-value>cse</param-value>
</init-param>
<init-param>
<param-name>password3</param-name>
<param-value>pvpsit</param-value>
</init-param>
<init-param>
<param-name>username4</param-name>
<param-value>wt</param-value>
</init-param>
<init-param>
<param-name>password4</param-name>
<param-value>lab</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Example</servlet-name>
<url-pattern>/ex1</url-pattern>
</servlet-mapping>
</web-app>
OUTPUT:
 |
| http://wikibrand.blogspot.in |
 |
| http://wikibrand.blogspot.in |
RESULT:
Thus the user authentication is carried out for four
users by using both cookies and getInitParameters successfully.
SOURCE:PVPSIT FOR JNTU
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