Question

I’m trying to do a simple insert query in mysql using java. How do I determine what the problem is if its not doing what its supposed to do:

import java.util.*;
import java.sql.*;
import javax.swing.JOptionPane;

public class regp {

    public regp(String player, int score) {
        conc conclass = new conc();
        Connection conn = conclass.dbConnect();


        try {



            PreparedStatement fetchPlayers = conn.prepareStatement("SELECT * FROM players WHERE P_Name='" + player + "'");
            ResultSet rs = fetchPlayers.executeQuery();

            if (rs.next()) {
                JOptionPane.showMessageDialog(null, "Already Registered!");
            } else {


                PreparedStatement createPlayer = conn.prepareStatement("INSERT INTO players(P_Name, Score) VALUES('" + player + "', '" + score + "')");

                createPlayer.execute();




                JOptionPane.showMessageDialog(null, "Player: " + player + " score: " + score);


                JOptionPane.showMessageDialog(null, "Registration Successful!");

                JOptionPane.showMessageDialog(null, "Not registered!");



            }
        } catch (Exception e) {
        }

    }
}

And heres conc.java which contains the database information:

import java.sql.*;
import java.util.*;

public class conc {

    public conc(){
    }

       public Connection dbConnect() {
        try {
            String db_connect_string="jdbc:mysql://localhost:3306/questions";
            String db_userid="root";
            String db_password="1234";
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            Connection conn = DriverManager.getConnection(db_connect_string, db_userid, db_password);


            return conn;

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

Problem is I don’t have any idea if its the query, the prepared statement declaration.
One thing is sure to be working. The part which checks if the player inputted is existing or not.
I already checked if the function is getting the values needed by outputting them using joptionpane message dialog. And it sure receives the correct values. So I’m thinking that maybe the problem is in the query.

Answer 1

You could print the exception that you’re catching in your regp constructor:

} catch (Exception e) {
    e.printStackTrace();
}

You may also want to look at prepared statements rather than constructing your SQL via string concatenation.