Ajax check Validate database Register Jsp & Servlet in Java NetBeans

Check database if true => image not-available.jpg

 Check database else false => image available.jpg

Class: DBUtil.java

Java 2016

private static Connection connection = null;

public static Connection getConnection() {
    if (connection != null) {
        return connection;
    } else {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/product", "root", "1234567");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }
}
//    //Test connection
//    public static void main(String[] args) {
//        System.out.println(getConnection());
//    }

Web Pages: Register.jsp

Java 2016

<form action="">
    <div>
        <span>Username*</span><br>
        <input type="text" name="username" id="username"><span id="user-result"></span><br>
    </div>
    <div>
        <span>Email*</span><br>
        <input type="text" name="email" id="email"><br>
    </div>                          
    <div> 
        <span>Password*</span><br>
        <input type="password"><br>
    <input type="submit" value="Register"> 
    </div>    
</form>

Ajax in Register.jsp

Java 2016

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
      $(document).ready(function () {
           var x_timer;
           $("#username").keyup(function (e) {
                clearTimeout(x_timer);
                var user_name = $(this).val();
                x_timer = setTimeout(function () {
                    check_username_ajax(user_name);
                }, 1000);
                });
 
           function check_username_ajax(username) {
                $("#user-result").html('<img src="img/ajax-loader.gif" />');
                $.post('CheckUserSevlet', {'username': username}, function (data) {
                    $("#user-result").html(data);
                 });
           }
       });
</script>

Servlet: CheckUserSevlet.java

Java 2016

UserDAO usersDAO = new UserDAO();

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    if (usersDAO.checkUser(request.getParameter("username"))) {
      response.getWriter().write("<img src=\"img/not-available.png\" />");
 } else {
      response.getWriter().write("<img src=\"img/available.png\" />");
 }
}

Class: UserDAO.java

Java 2016

public boolean checkUser(String username) {
    Connection conn = DBUtils.getConnection();
    try {
        PreparedStatement stmt = conn.prepareStatement("Select * from product.users where user_name='" + username + "'");
        ResultSet rs = stmt.executeQuery();
        if (rs.next()) {
            conn.close();
            return true;
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return false;
}
//Test boolean
//    public static void main(String[] args) {
//        UserDAO d = new UserDAO();
//        System.out.println(d.checkUser("tony"));
//    }

web.xml

Java 2016

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
    <servlet>
        <servlet-name>CheckUserSevlet</servlet-name>
        <servlet-class>servlet.CheckUserSevlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CheckUserSevlet</servlet-name>
        <url-pattern>/CheckUserSevlet</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

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