Servlet - CRUD

// Model file equivalent 
// to MySQL table GeekUsers
public class GeekUsers {
    private int geekUserId;
    private int numberOfPosts;
    private String geekUserName, technologiesPreferred;

    public int getId() { return geekUserId; }

    public void setId(int id) { this.geekUserId = id; }

    public String getName() { return geekUserName; }

    public void setName(String name)
    {
        this.geekUserName = name;
    }

    public int getNumberOfPosts() { return numberOfPosts; }

    public void setNumberOfPosts(int numberOfPosts)
    {
        this.numberOfPosts = numberOfPosts;
    }

    public String gettechnologiesPreferred()
    {
        return technologiesPreferred;
    }

    public void
    setTechnologiesPreferred(String technologiesPreferred)
    {
        this.technologiesPreferred = technologiesPreferred;
    }
}

import java.util.*;
import java.sql.*;  
public class GeekUsersDao { 
  
    // Here geeksforgeeks is the name of the database
    private static String jdbcURL = "jdbc:mysql://localhost:3306/geeksforgeeks";
    private static String jdbcUsername = "root";
  
    // provide your appropriate password  here
    private static String jdbcPassword = "*****"; 

    public static Connection getConnection(){
        Connection con=null;        
        try {
             // This is the way of connecting MySQL
            Class.forName("com.mysql.jdbc.Driver"); 
            con = DriverManager.getConnection(jdbcURL, jdbcUsername, jdbcPassword);
        } catch (SQLException e) {
            System.out.println("Message.. " + e.getMessage());
            e.printStackTrace();            
        } catch (ClassNotFoundException e) {
            System.out.println("Message.. " + e.getMessage());
            e.printStackTrace();
        }        
        return con;
    }
    // Rest of the methods like Save,
    // Update, Delete etc., should come here
}

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/SaveServlet")
public class SaveGeekUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request,
                          HttpServletResponse response)
        throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        // Getting all the request parameters from
        // index.html
        String name = request.getParameter("name");
        int numberOfPosts = Integer.parseInt(
            request.getParameter("numberOfPosts"));
        String technologiesPreferred
            = request.getParameter("technologiesPreferred");

        // GeekUsers object is created
        GeekUsers geekUser = new GeekUsers();

        // Collected parameters like name, numberOfPosts and
        // technologiesPreferred are set for the object so
        // that it can be retrieved in other places
        geekUser.setName(name);
        geekUser.setNumberOfPosts(numberOfPosts);
        geekUser.setTechnologiesPreferred(
            technologiesPreferred);

        // Calling save method in GeekUsersDao by passing
        // geekUser
        int status = GeekUsersDao.save(geekUser);

        // This is possible when the record is saved
        // successfully
        if (status > 0) {
            out.print("



<p>Record saved successfully!</p>



");
            request.getRequestDispatcher("index.html")
                .include(request, response);
        }
        else {
            // If there is an issue in saving the record, we
            // need to show this message
            out.println("Sorry! unable to save record");
        }

        out.close();
    }
}

public static int save(GeekUsers e)
{
    int status = 0;
    try {
        Connection con = GeekUsersDao.getConnection();
        // Using PreparedStatement, we can execute any SQL
        // statement In order to save the record, we need to
        // insert the details in 'geekusers' table "e" is an
        // object of type "GeekUsers" which exactly resembles
        // geekusers table From html page, the values has
        // been passed to a servlet and from there, this
        // method is called
        PreparedStatement ps = con.prepareStatement(
            "insert into geekusers(geekUserName,numberOfPosts,technologiesPreferred) values (?,?,?)");
        ps.setString(1, e.getName());
        ps.setInt(2, e.getNumberOfPosts());
        ps.setString(3, e.gettechnologiesPreferred());

        status = ps.executeUpdate();

        con.close();
    }
    catch (Exception ex) {
        System.out.println("Message.." + ex.getMessage());
        ex.printStackTrace();
    }

    return status;
}

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/ViewServlet")
public class ViewGeekUserServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter printWriter=response.getWriter();
        printWriter.println("<a href='index.html'>Add New GeekUser</a>");
        printWriter.println("<h1>GeekUsers List</h1>");
        
        List<GeekUsers> list=GeekUsersDao.getAllGeekUses();
        
        printWriter.print("<table border='1' bordercolor='#009879' width='50%'");
        printWriter.print("<tr><th>Id</th><th>Name</th><th>Number Of Post</th><th>Preferred Technology</th><th>Edit</th><th>Delete</th></tr>");
        for(GeekUsers e:list){
            // each row is identified by means of its id
            // hence on click of 'edit', it is sent as
            // <a href='EditServlet?id="+e.getId()+"'>edit</a>
            // on click of 'delete', it is sent as
            // <a href='DeleteServlet?id="+e.getId()+"'>delete</a>
            printWriter.print("<tr><td >"+e.getId()+"</td><td>"+e.getName()+"</td><td>"+e.getNumberOfPosts()+"</td><td>"+e.gettechnologiesPreferred()+"</td><td><a href='EditServlet?id="+e.getId()+"'>edit</a></td><td><a href='DeleteServlet?id="+e.getId()+"'>delete</a></td></tr>");
        }
        printWriter.print("</table>");
        
        printWriter.close();
    }
}

public static List<GeekUsers> getAllGeekUses()
{
    List<GeekUsers> list = new ArrayList<GeekUsers>();

    try {
        Connection con = GeekUsersDao.getConnection();
        PreparedStatement ps = con.prepareStatement(
            "select * from geekusers");
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            GeekUsers e = new GeekUsers();
            e.setId(rs.getInt(1));
            e.setName(rs.getString(2));
            e.setNumberOfPosts(rs.getInt(3));
            e.setTechnologiesPreferred(rs.getString(4));
            list.add(e);
        }
        con.close();
    }
    catch (Exception e) {
        e.printStackTrace();
    }

    return list;
}

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/EditServlet")
public class EditGeekUserServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out=response.getWriter();
        out.println("<h1>Update GeekUser</h1>");
        String sid=request.getParameter("id");
        int id=Integer.parseInt(sid);
      
        // We need to get the id from view servlet
        // request and it has to be parsed with
        // Integer.parseInt in order to get as number
        // Then specific user is retrieved by means 
        // of GeekUsersDao.getGeekUsersById(id)
        GeekUsers e=GeekUsersDao.getGeekUsersById(id);
        
        out.print("<form action='EditServlet2' method='post'>");
        out.print("<table>");
        out.print("<tr><td></td><td><input type='hidden' name='id' value='"+e.getId()+"'/></td></tr>");
        out.print("<tr><td>Name:</td><td><input type='text' name='name' value='"+e.getName()+"'/></td></tr>");
        out.print("<tr><td>Number Of Posts:</td><td><input type='text' name='numberOfPosts' value='"+e.getNumberOfPosts()+"'/></td></tr>");
        out.print("<tr><td>Technologies Preferred:</td><td><input type='text' name='technologiesPreferred' value='"+e.gettechnologiesPreferred()+"'/></td></tr>");
        
        out.print("<tr><td colspan='2'><input type='submit' value='Edit & Save '/></td></tr>");
        out.print("</table>");
        out.print("</form>");
        
        out.close();
    }
}

public static GeekUsers getGeekUsersById(int id)
{
    GeekUsers e = new GeekUsers();

    try {
        Connection con = GeekUsersDao.getConnection();
        // We are getting the details for a specific user
        // and hence the query has to be sent in the below
        // way
        PreparedStatement ps = con.prepareStatement(
            "select * from geekusers where geekUserId=?");
        ps.setInt(1, id);
        ResultSet rs = ps.executeQuery();
        if (rs.next()) {
            e.setId(rs.getInt(1));
            e.setName(rs.getString(2));
            e.setNumberOfPosts(rs.getInt(3));
            e.setTechnologiesPreferred(rs.getString(4));
        }
        con.close();
    }
    catch (Exception ex) {
        ex.printStackTrace();
    }

    return e;
}

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/EditServlet2")
public class EditGeekUserServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out=response.getWriter();
        
        String sid=request.getParameter("id");
        int id=Integer.parseInt(sid);
        String name=request.getParameter("name");
        int numberOfPosts=Integer.parseInt(request.getParameter("numberOfPosts"));
        String technologiesPreferred=request.getParameter("technologiesPreferred");    
        
        GeekUsers geekUser=new GeekUsers();
        geekUser.setId(id);
        geekUser.setName(name);
        geekUser.setNumberOfPosts(numberOfPosts);
        geekUser.setTechnologiesPreferred(technologiesPreferred);
        
        // GeekUsersDao.update method is called
        // along with the modified values for geekUser
        int status=GeekUsersDao.update(geekUser);
        if(status>0){
            response.sendRedirect("ViewServlet");
        }else{
            out.println("Sorry! unable to update record");
        }
        
        out.close();
    }

}

public static int update(GeekUsers e)
{
    int status = 0;
    try {
        Connection con = GeekUsersDao.getConnection();
        // AS we are not sure about what fields need to be
        // updated, we are setting for all the fields by
        // means of update query This will update the record
        // for the corresponding geekUserId
        PreparedStatement ps = con.prepareStatement(
            "update geekusers set geekUserName=?,numberOfPosts=?,technologiesPreferred=? where geekUserId=?");
        ps.setString(1, e.getName());
        ps.setInt(2, e.getNumberOfPosts());
        ps.setString(3, e.gettechnologiesPreferred());
        ps.setInt(4, e.getId());

        status = ps.executeUpdate();

        con.close();
    }
    catch (Exception ex) {
        ex.printStackTrace();
    }

    return status;
}

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/DeleteServlet")
public class DeleteGeekUserServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response)
        throws ServletException, IOException
    {
        String sid = request.getParameter("id");
        int id = Integer.parseInt(sid);
        // GeekUsersDao.delete method is called with the
        // corresponding id and then it is redirected to
        // viewservlet
        GeekUsersDao.delete(id);
        response.sendRedirect("ViewServlet");
    }
}

public static int delete(int id)
{
    int status = 0;
    try {
        Connection con = GeekUsersDao.getConnection();
        // delete query is given to delete the record for
        // the given geekUserId
        PreparedStatement ps = con.prepareStatement(
            "delete from geekusers where geekUserId=?");
        ps.setInt(1, id);
        status = ps.executeUpdate();
        con.close();
    }
    catch (Exception e) {
        e.printStackTrace();
    }

    return status;
}