jdbc链接mysql数据库，并查询

package servlet;

import java.io.IOException;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet extends HttpServlet {
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");
    request.setCharacterEncoding("utf-8"); 
    //注册驱动
     try {
      Class.forName("com.mysql.jdbc.Driver");
      // 获取连接
      Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/school","root","ok");
       //得到执行语句的statement对象
       Statement statement = connection.createStatement();
       String sql="select * from grade";
       ResultSet resultSet = statement.executeQuery(sql);
      while ( resultSet.next()) {
        System.out.println(resultSet.getInt(1)+resultSet.getString(2));
        //第一列是Int类型的。第二列是String类型。
      }
      statement.close();
      connection.close();
    } catch (ClassNotFoundException e) {
      e.printStackTrace();
    } catch (SQLException e) {   
      e.printStackTrace();
    }
  }
  public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
          doGet(request, response);
    response.setContentType("text/html");
  }
}