how can i prevent duplicate records using servlets and MVC model?

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how can i prevent duplicate records using servlets and MVC model?

hai,

I need a program to insert values into database at the same time it shows error msg on response page while we are giving duplicate entry of a primary key.i want this program in MVC model.can anyone help me...

Thanks&Regards P.Divya

View Answers

April 27, 2011 at 5:21 PM

1)form4.jsp:

<html>
<form method="post" action="../InsertServlet">
<table>
<tr><td>Id:</td><td><input type="text" name="id"></td></tr>
<tr><td>Name:</td><td><input type="text" name="name"></td></tr>
<tr><td>Address:</td><td><input type="text" name="address"></td></tr>
<tr><td>Contact No:</td><td><input type="text" name="contact"></td></tr>
<tr><td>Email:</td><td><input type="text" name="email"></td></tr>
<tr><td></td><td><input type="submit" value="Submit"></td></tr>
</table>
</form>
</html>

2)InsertServlet.java:

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

public class InsertServlet extends HttpServlet{ 
    public void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException,IOException {
        res.setContentType("text/html");
        int count=0;
        PrintWriter out = res.getWriter();
        int id=Integer.parseInt(req.getParameter("id"));
        String name=req.getParameter("name");
        String address=req.getParameter("address");
        int phone=Integer.parseInt(req.getParameter("contact"));
        String email=req.getParameter("email");
        try{
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
        Statement st=con.createStatement();
        ResultSet rs=st.executeQuery("select * from employee where id='"+id+"'");
        while(rs.next()){
        count++;
        }
        if(count>0){
        out.println("<font color=red>Error: Id already exists</font>");

        }
        else{
         int i=st.executeUpdate("insert into employee(id,name,address,contactNo,email) values("+id+",'"+name+"','"+address+"',"+phone+",'"+email+"')");
        out.println("<font color=green>Data is successfully inserted!</font>");
        }
        }
        catch(Exception e){
        System.out.print(e);
                }       
            }
        }

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