02Mybatis_原生态jdbc编程中的问题总结——从而引生出为什么要用Mybatis

package cn.itcast.mybatis.jdbc;

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



public class jdbc {

    public static void main(String[] args) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        
        try {
            //加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
            
            //通过驱动管理类获取数据库链接
            connection =   DriverManager.getConnection("jdbc:mysql://localhost:3306/mybaits?characterEncoding=utf-8", "root", "root");
            //定义sql语句 ?表示占位符
        String sql = "select * from user where username = ?";
            //获取预处理statement
            preparedStatement =  connection.prepareStatement(sql);
            //设置参数，第一个参数为sql语句中参数的序号（从1开始），第二个参数为设置的参数值
            preparedStatement.setString(1, "王五");
            //向数据库发出sql执行查询，查询出结果集
            resultSet =  preparedStatement.executeQuery();
            //遍历查询结果集
            while(resultSet.next()){
                System.out.println(resultSet.getString("id")+"  "+resultSet.getString("username"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            //释放资源
            if(resultSet!=null){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(preparedStatement!=null){
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(connection!=null){
                try {
                    connection.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }

    }

}