Example2 : Servlet that checks user details
- This example explains how to validate login details and send back the response accordingly
- Create following files in a folder (Please check next slide for code)
- Java File LoginServlet.java Contains logic - check user details and send response
- DD web.xml Contains deployment details. Deployment Descriptor
- HTMLFile index.html Contains html that allows user to enter details
- Compile the Java File as you did in earlier example
- Create below structure with files that you created above
- Folder "LoginServlet" contains
- I__ "WEB-INF" Folder and index.html
- I__"WEB-INF" Folder contains "classes" Folder and web.xml File
- I__"classes" Folder contains "LoginServlet.class" File
- Deploy the LoginServlet folder inside webapps folder of Tomcat
- Bounce the Server
- Send request using "http://localhost:8550/LoginServlet/index.html"
LoginServlet.java : This prepares the
response as HTML file that displays if user provided values are correct or not
import java.io.IOException;
import java.io. PrintWriter;
import java.sql.*;
import
javax.servlet.RequestDispatcher;
import
javax.servlet.ServletException;
import javax.servlet.
http.HttpServlet;
import javax.servlet.
http.HttpServletRequest;
import javax.servlet.
http.HttpServletResponse;
public class LoginServlet
extends HttpServlet {
public void
doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, I0Exception {
response.setContentType("text/html");
PrintWriter
out = response.getWriter();
String
n=request.getParameter("username");
String
p=request.getParameter("userpass");
if(validate(n, p)){
out.printin("
<html>");
out.println("</head>");
out.printin("<body>");
outprintln("<h1>Hello
"+n+"</h1>");
outprintln("!!!!! Our
Site is under construction. Please come back!!!!!");
out.println("</body>");
out.println("</html>");
}
else {
out.println("<html>");
out.println("<body>");
out.println("<h1>Check
your credentials</h1>");
outprintln("!!!!!
I am very strong.. I cannot allow strangers !!!!!");
out.println("</body>");
out.
println("</html>");
}
out.close();
}
public static boolean
validate(String name,String pass){
if(name.equals("arun")
&& pass.equals("password1"))
return true;
else
if(name.equals("kiran") &&
pass.equals("password2"))
return true;
else
return false;
}
}
- web.xml
- <servlet> tag maps your servlet class with internal name
- <servlet-mapping> tag maps internal name with url-pattern that your invoke
<web-app
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/web-app_2_4.xsd"
version="2.4">
<servlet>
<servlet-name>loginexample</servlet-name>
<servlet-class>
LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>loginexample</servlet-name>
<url-pattern>/loginpage.doqurl-pattern>
</servlet-mapping>
</web-app>
index.html
<html>
<body>
<h1 align="center">Welcome to Our
Website</h1>
<h2
align="center">Please provide your credentials to login</h2>
<form
action="loginpage.do" method="post">
Name :
<input type="text" name="username"/> <br/>
<br/>
Password: <input
type="password" name="userpass"/><br/><br/>
<input
type="submit" value="login"/>
</form>
</body>
</html>
Output: http://localhost:8550/LoginServlet/index.html
In
our servlet class, we used static username/password. Instead you can validate
the data against the details from database also.
