public void UpdateUserDATA(User user) throws SQLException {
     PreparedStatement preparedStatement =null;
    try {
                    Connection connection = getConnection();
            preparedStatement = connection.prepareStatement("update userregisteration set firstName=?, lastName=?, username=?,password=?, telephone=?, address=?  where username=? ");
        preparedStatement.setString(1, user.getFirst_name());
                    preparedStatement.setString(2, user.getLast_name());
                    preparedStatement.setString(3, user.getUsername());
                    preparedStatement.setString(4, user.getPassword());
                    preparedStatement.setString(5, user.getContactNo());
                    preparedStatement.setString(6, user.getAddress());
                    preparedStatement.setString(7, user.getUsername());
                    preparedStatement.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {

        if (preparedStatement != null) {
            preparedStatement.close();
        }
    }

}

package Controller;

import DatabaseConnector.DatabaseConnectivity;
import DatabaseConnector.UserDataConnector;
import java.io.IOException;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import model.User;


/**
 *
 * @author Thanuka_Senadheera
 */
public class UserUpdateServlet extends HttpServlet {


 private final DatabaseConnectivity DBConnection = new DatabaseConnectivity();



    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
    {

        resp.setContentType("text/html;charset=UTF-8");


        if (!DBConnection.ConnectionValid())
        {
            resp.sendRedirect("404/404.html"); //Connection to the database was not successful
        }
        else
        {
             HttpSession session = req.getSession();
             String username = (String) session.getAttribute("username");
             String password = (String) session.getAttribute("password");
           if (DBConnection.UserValidation(username, password))
            {
                UserDataConnector UDC = new UserDataConnector();
                User user = (User) session.getAttribute("user");
                 try {
                     UDC.UpdateUserDATA(user);
                 } catch (SQLException ex) {
                     Logger.getLogger(UserUpdateServlet.class.getName()).log(Level.SEVERE, null, ex);
                 }
                session.setAttribute("user",user);
                req.setAttribute("message","Your details are successfully updated, Please Go to home page!");
                resp.sendRedirect("manageAccounts.jsp");
            }
           else
           {
               req.setAttribute("message","Account is invalid, Please SignUp!");
               req.getRequestDispatcher("Login.jsp").forward(req,resp);
           }
    }
   }


}

package model;

import java.io.Serializable;

/**
 *
 * @author Thanuka_Senadheera
 */
public class User implements Serializable
{
    private String first_name;
    private String last_name;
    private String username;
    private String password;
    private String contactNo;
    private String address;

    public User(String first_name,String last_name,String username,String password,String contactNo,String address)
    {
        this.first_name=first_name;
        this.last_name=last_name;
        this.username=username;
        this.password=password;
        this.contactNo=contactNo;
        this.address=address;

    }

    public User()
    {

    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public void setContactNo(String contactNo) {
        this.contactNo = contactNo;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getFirst_name() {
        return first_name;
    }

    public String getLast_name() {
        return last_name;
    }

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }

    public String getContactNo() {
        return contactNo;
    }

    public String getAddress() {
        return address;
    }


    /*
    @Override
    public String toString() {
        return "User [first_name=" + first_name + ", last_name=" + last_name
                + ", username=" + username + ", password=" + password + ", contactNo="
                + contactNo + ", address=" + address + "]";
    }
    */

}


----------------------------------------------------------------------