How To Connect To A Database In Java

This source codes, written in Java, demonstrates how to connect to a database using JDBC and ODBC. The source codes is well commented for you to follow easily.

import java.sql.*;

public class jdbcConnect {
  //CLASS CONSTRUCTOR
  public jdbcConnect() {
  }

  //THIS PROC WILL SET THE CONNECTION TO THE DATABASE,
  //QUERY AND PRINT THE RESULT TO THE STANDARD OUTPUT
  private void loadData()
  {
  Connection con = null;
  Statement stmt = null;
  ResultSet rst = null;

    //SET ERROR TRAP FOR CONNECTION TO THE DATABASE
    try
      {
      //FOR ODBC CONNECTION
      Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
      //dsn_employee  = data source name(dsn)
      //un      = username
      //pw      = password
      con = DriverManager.getConnection("jdbc:odbc:dsn_employee;
                         UID=un;PWD=pw");

      //CHECK IF THE CONNECTION TO THE DATABASE IS SUCCESSFUL
      if(!con.isClosed())
        {
        //MAKE THE ACTUAL CONNECTION TO THE DATABASE
        stmt = con.createStatement(rst.TYPE_SCROLL_SENSITIVE,
                       rst.CONCUR_READ_ONLY);
        //EXECUTE THE SQL QUERY
        rst = stmt.executeQuery("SELECT fullname FROM employee");

        //CHECK IF CURRENT ROW IS THE LAST
        while(!rst.isLast())
          {
          //SET THE ERROR TRAP FOR READING THE RECORDSET
          try
            {
            //GO TO THE NEXT RECORD OF THE RECORDSET
            rst.next();
            //PRINT THE RECORD TO THE STANDARD OUTPUT
            System.out.println(rst.getInt("fullname"));
            }
          //HANDLE TRAPPED ERROR ON READING THE RECORDSET
          catch(Exception e)
            {
            //PRINT THE ERROR MESSAGE
            System.out.println("ERROR: " + e.getMessage());
            }
          }
        }
      }
    //HANDLE TRAPPED ERROR ON DATABASE CONNECTION
    catch(Exception e)
      {
      //PRINT THE ERROR MESSAGE
      System.err.println("ERROR: " + e.getMessage());
      }
    finally
      {
      try
        {
        if(con != null)
          {
          //CLOSE THE CONNECTION
          con.close();
          }
        }
      catch(SQLException e)
        {
        //PRINT THE ERROR MESSAGE
        System.out.println("ERROR: " + e.getMessage());
        }
      }
    }

  //START OF PROGRAM
  public static void main(String[] args) {
    jdbcConnect dbConnect = new jdbcConnect();
    dbConnect.loadData();
  }
}