Java/J2EE tutorials with source code

Hey guys, today we are gonna be developing the username availability application based on the real world scenario and using the technologies which are used across almost all the major IT firms.

Before we begin writing the code I'd assume that you guys have following software installed.

Eclipse IDE
Tomcat app server
MySQL Database

Alright, first of all we are going to start the DB and will create the database and the table. After that we can enter some test values. Check the script below.
MySQL Script:

create database students;

create table users(
 uid int primary key 
        auto_increment,
 uname varchar(20) unique
 );

INSERT INTO `students`.`users` 
(`uid`, `uname`) VALUES ('1', 
'Amjad');INSERT INTO 
`students`.`users` (`uid`, 
`uname`) VALUES ('2', 'Amzi');

Create a dynamic web project in your IDE workspace and the project structure should look something like this.

Next are going to create the view using jsp, the view will consist of a simple text box which will check if the input string value is 3 character long or not. If yes then it will go ahead and make a query and will check the availability of the username.

index.jsp



Username Availability


 


 
  User Name :

Now, we are going to write a servlet which will create a database connection and make a query to it.
CheckAvailability.java

package com.amzi.servlets;

import java.io.*;
import java.sql.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class CheckAvailability extends HttpServlet {

 private static final long serialVersionUID = -734503860925086969L;

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {

            String connectionURL = "jdbc:mysql://localhost:3306/students"; // students is my database name
            Connection connection = null;
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            connection = DriverManager.getConnection(connectionURL, "root", "password");
            String uname = request.getParameter("uname");
            PreparedStatement ps = connection.prepareStatement("select uname from users where uname=?");
            ps.setString(1,uname);
            ResultSet rs = ps.executeQuery();
             
            if (!rs.next()) {
                out.println(""+uname+" is avaliable");
            }
            else{
            out.println(""+uname+" is already in use");
            }
            out.println();

        } catch (Exception ex) {
            out.println("Error ->" + ex.getMessage());
        } finally {
            out.close();
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }
}

Also, we can configure the deployment descriptor as follows.
web.xml



    
        check
        com.amzi.servlets.CheckAvailability
    
    
        check
        /check
    
    
        
            30
        
    
    
        index.jsp

Note: In addition to these code we also need jquery library and mysql connector jar file. Just in case you are unable to find those, you may click here to get the complete source code.

Now, we are all set to deploy and test the code on the server. We can hit the below url
http://localhost:8080/UserAvailability/
And, the page will look something like this

Check username availability using Java, JSP, AJAX, MySQL, JDBC, Servlet