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

public class mySQLEngine {

    private Connection conn;
    private String url, userName, password, catalogue;

    public mySQLEngine(String userName, String password){

        conn = null;
        this.userName = userName;
        this.password = password;
    }

    public void connnect() {

        InputStream is = getClass().getResourceAsStream("mySQLEngine.properties");
        Properties p = new Properties();

        try {
            p.load(is);
            url = p.getProperty("connectionURL");
            catalogue = p.getProperty("catalogue");
        }
        catch (IOException e) {
            System.err.println("error loading properties...");
        }
        try
          {

            Class.forName("com.mysql.jdbc.Driver").newInstance ();

            conn = DriverManager.getConnection(url+catalogue, userName, password);
            System.out.println ("Database connection established");
          }
          catch (Exception e)
          {
              System.err.println ("Cannot connect to database server");

          }
    }

    public void closeConnection(){

        try {
            conn.close();

        } catch (SQLException e) {
            System.err.println("SQLException: " + e.getMessage());

        }
    }

    public ResultSet executeQuery(String sqlStatement) throws SQLException{
        ResultSet rs = null;

        try{
            Statement stmt = conn.createStatement();

            if(stmt.execute(sqlStatement)){
                rs = stmt.getResultSet();

            }
        }
        catch (SQLException e) {
            throw e;
        }

        return rs;
    }