import java.sql.*;

class Mysql{
 private String url="jdbc:mysql://localhost:3306/jdbcTest";
 private String username = "root";
 private String password = "139689";

 public Connection getConnection(){
  Connection con = null;
  try{
  
   Class.forName("com.mysql.jdbc.Driver");
   con = DriverManager.getConnection(url,username,password);
   return con;
  }catch(ClassNotFoundException e){
   System.out.println("加载类驱动错误");
   System.out.println(e);
  }catch(Exception e){
   System.out.println(e);
  }
  return null;
 }

 public ResultSet executeSql(String sql){
 
  Connection con;
  Statement stmt;

  try{
   con = getConnection();
   stmt = con.createStatement();
   ResultSet rs = stmt.executeQuery(sql);
   return rs;
  }catch(SQLException e){
   System.out.println("获取数据失败");
  }
  return null;
 }
}

public class jdbcTest{
 public static void main(String[] args){
  Mysql mysql = new Mysql();
  Connection con = null;
  ResultSet rs = null;
  rs = mysql.executeSql("select * from user");
  try{
   while(rs.next()){
    System.out.println(rs.getString("username"));
   }
  }catch(Exception e){
   System.out.println(e.getMessage());
  }
 }
}