ecj – Programmerbay

Create an application to add and multiply two numbers to the servlet to the user in apache tomcat server

Sandeep Verma — Sat, 07 Nov 2020 14:34:36 +0000

We are assuming that you have already downloaded and setup the Eclipse Environment and Tomcat server.

Here are the steps and the code to add and multiply two numbers to servlet in apache tomcat server

1) On Eclipse, create a new project and select Dynamic Web Project by ticking on producing deployment descriptor file.

2. Firstly hover on your newly created project, right-click on it and tab on new and select HTML file. ( or anything you want).

Index.html




Practical Work



First number   


Second number

3. Now, again hover on the project , right click on it and select new and tab on class that would create a java file.

Create a servlet class.

Add_Numbers.java

package com.programmerbay;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.*;
public class Add_Numbers extends HttpServlet{
public void service(HttpServletRequest request,HttpServletResponse response) throws IOException
{
int num1 = Integer.parseInt(request.getParameter("num1"));
int num2 = Integer.parseInt(request.getParameter("num2"));
int sum = num1 + num2;
int product = num1 * num2;
PrintWriter output = response.getWriter();
output.println("The Answer :"+sum +"\n The product :"+product);
}
}

4. Configure the Web.xml file which you find in Web Content folder.

web.xml





Add
com.programmerbay.Add_Numbers





Add
/add_me

5. Open the previously created index.html and run it by selecting the “restart server”.

Output:

Create an application with two textboxes username and password on receiving the request to the user details and display welcome username on another page

Sandeep Verma — Sun, 08 Dec 2019 13:55:58 +0000

In this article, we’re going to look at a basic login verification form using JSP and servlet. If a user’s entered username and password matches with original username and password then ‘welcome’ page would open.

Here’s the code with two textboxes username and password on receiving the request to verify the user details and display welcome username on another page.

1.Make a landing page in JSP where two text boxes and a submit button will be displayed.

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>




Practical Work


<% 
String msg = (String) request.getAttribute("message"); 
if(msg==null)
  out.println("\t");
else
out.println(msg);
%>

Username :  
Password :

2. Now, it’s time to verify the user which would be done by servlet at backend.

login.java

package com.programmerbay;

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;

public class login extends HttpServlet{
  public void service(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException
  {
    
  String username = request.getParameter("username")	;
  String password = request.getParameter("pass")	;
    if(username.equals("programmerbay") && password.equals("12345"))
  {
HttpSession session = request.getSession();
session.setAttribute("username", username);
  response.sendRedirect("home.jsp");
  }
  else
  {
    String msg;
    if(username.isEmpty() || password.isEmpty())
    msg ="Fields are  empty";
    else
    msg ="Password is incorrect!!";
    request.setAttribute("message", msg);
        
    RequestDispatcher redirect = request.getRequestDispatcher("index.jsp");
    redirect.forward(request,response);
  }
  }

}

3. If a user type in correct username and password, ‘welcome’ page would be displayed.

Home.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>




Home


<%
String username = (String)session.getAttribute("username");
if(username==null)
{
  response.sendRedirect("index.html");
}
%>

This is home Screen

4. To end the session, a logout servlet will work whenever a user clicks on the logout button.

logout.java

package com.programmerbay;

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;

public class logout extends HttpServlet{
  public void service(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException
  {
    HttpSession session = request.getSession();
    session.removeAttribute("username");
    session.invalidate();
    response.sendRedirect("index.jsp");
  }
}

Output:

When either username or password is not entered

When a user enters a wrong password or username

Homepage

Create an application to show how to call a servlet from another servlet using sendRedirect method in apache tomcat server

Sandeep Verma — Sat, 07 Dec 2019 15:20:38 +0000

There is another way to call a servlet from another servlet using sendRedirect method.
1) Create Index.html file by clicking on ‘new’ tab and select HTML.

Index.html





Practical Work



WRITE

2) Create a servlet that will redirect to another servlet. In order to send data, one requires to maintain a session.

First_Servlet.java

package com.programmerbay;

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;

public class First_Servlet extends HttpServlet{
  public void service(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException
  {
  String word = request.getParameter("word")	;
  PrintWriter output = response.getWriter();
  
String word1 = word+".\n Now, It is calling second servlet";
  // redirecting it to second servlet
HttpSession session = request.getSession();
session.setAttribute("word", word1);
  response.sendRedirect("second_servlet");
  }

}

3) Write another servlet that will handle the data sent from the first servlet and print the message.

Second_Servlet.java

package com.programmerbay;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class Second_Servlet extends HttpServlet{
  public void service(HttpServletRequest request,HttpServletResponse response) throws IOException
  {
    HttpSession session = request.getSession();
    String word = (String) session.getAttribute("word");
    PrintWriter output = response.getWriter();
    output.println(word+" \n usiing session");
    
  }
}

4) Modify the Web.xml file to map servlets.

web.xml



  


 
 Invoke_First
 com.programmerbay.First_Servlet
 
 
 
 
 
 Invoke_First
 /first_servlet
 
 
 
 
 Invoke_Second
 com.programmerbay.Second_Servlet
 
 
 
 
 
 Invoke_Second
 /second_servlet

Output:

Create an application to call a servlet from another servlet using RequestDispatcher in apache tomcat server

Sandeep Verma — Sat, 07 Dec 2019 15:10:49 +0000

Here’s the code to invoke a servlet from another servlet using RequestDispatcher interface.
1) Create index.html.

Index.html





Practical Work



WRITE

2) Now, create a basic servlet and pass the data of textbox field from index.html to First_Servlet.java. Use requestdispatcher to rely the data to other servlet.

First_Servlet.java

package com.programmerbay;

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;

public class First_Servlet extends HttpServlet{
public void service(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException
{
String word = request.getParameter("word") ;
PrintWriter output = response.getWriter();

String word1 = word+".\n Now, It is calling second servlet";
// Dispatching it to second servlet
RequestDispatcher redirecting = request.getRequestDispatcher("second_servlet");
request.setAttribute("passingWord", word1);
redirecting.forward(request, response);
}

}

3) After that, write the code for second servlet that will handle the message or information from first servlet.

Second_Servlet.java

package com.programmerbay;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Second_Servlet extends HttpServlet{
public void service(HttpServletRequest request,HttpServletResponse response) throws IOException
{
String word = (String) request.getAttribute("passingWord");
PrintWriter output = response.getWriter();
output.println(word);

}
}

4) Edit the deployment descriptor.

Web.xml





Invoke_First
com.programmerbay.First_Servlet





Invoke_First
/first_servlet




Invoke_Second
com.programmerbay.Second_Servlet





Invoke_Second
/second_servlet

Output: