before inserting check already existing data in database - mysql

Question

Register.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
*
* #author srini
*/
#WebServlet(urlPatterns = {"/RegisterServlet"})
public class RegisterServlet extends HttpServlet {
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* #param request servlet request
* #param response servlet response
* #throws ServletException if a servlet-specific error occurs
* #throws IOException if an I/O error occurs
*/
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws IOException,ServletException{
processRequset (request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequset (request,response);
}
#SuppressWarnings("unused")
public void processRequset(HttpServletRequest request,HttpServletResponse response)
throws IOException,ServletException{
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String phone =request.getParameter("phone");
String username =request.getParameter("uname");
String password =request.getParameter("pass");
try{
Class.forName("com.mysql.jdbc.Driver");
Connection con=DriverManager.getConnection(
"jdbc:mysql://localhost:3306/register","root","toor");
PreparedStatement pstmt=con.prepareStatement("select * from headwy where unmae=? " );
ResultSet rs = pstmt.executeQuery();
if(rs.next()==true)
{
out.print("username already exist");
}
else {
String insertquery = "insert into headwwy (phone,uname,pass) values(?,?,?)";
pstmt.executeQuery("insertquery");
pstmt.setString(1,phone);
pstmt.setString(2,username);
pstmt.setString(3,password);
out.print("You are successfully registered...");
pstmt.close();
con.close();
}
}
catch (Exception e2) {System.out.println(e2);
}
out.close();
}
}
I am trying to check the existing data in database and insert the record.In the above try to execute it shows the blank page.
before insert command is worked but we adding the select command its not working.
using the select command for the check the database and in case any data existing the database it shows the record is already exist ,please choose the another name.
In case of no duplicate data not found,insert command perform the action and insert the new record into the database and it shows the new record in to database successfully.
But my code is not working for the properly.
thank you.

Answer 1

You have mistake in your code :
PreparedStatement pstmt=con.prepareStatement("select * from headwy where unmae=? " );
check your column name its "uname" not "unmae".

Answer 2

There are multiple issues in your code. First there is a typo. If that is the reason for failure.
select * from headwy where unmae=?
insert into headwwy (phone,uname,pass) values(?,?,?)
Also
pstmt.executeQuery("insertquery");
should be executed after you have set the parameters
pstmt.setString(1,phone);
pstmt.setString(2,username);
pstmt.setString(3,password);
I'll recommend to go through JDBC tutorial and run again.

Answer 3

You should set the parameters in your preparedstatement before executing your preparedstatement.
PreparedStatement pstmt=con.prepareStatement("select * from headwy where unmae=? " );
pstmt.setString(1,username);
ResultSet rs = pstmt.executeQuery();
if(rs.next())
{
System.out.print("username already exist");
}