访问数据库的工具类

1、工具类

package cn.zmh.Utils;


import java.sql.*;
/*
 * 访问数据库的工具类
 * */
public class JdbcUtils {
    // 1 可以把几个字符串定义成常量
    private static final String USER = "root";
    private static final String UPWD = "root";
    private static final String URL = "jdbc:mysql:///qy97";
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    // 2 注册驱动
    static{
        try {
            Class.forName(DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    // 3 得到数据库连接
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL,USER,UPWD);
    }
    // 4 关闭连接  执行 的打开资源
    public static void close(Connection connection, Statement statement){
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    // 5 关闭所有的打开资源
    public static void close(Connection connection, Statement statement, ResultSet rs){
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

2、事物    调用工具类模拟银行转账

package cn.zmh.Transcation转账;

import cn.zmh.Utils.JdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
 * 事物   模拟银行转账
 * */
public class TranscationDemo {
    public static void main(String[] args) {
        // 声明变量
        Connection conn = null;
        PreparedStatement ps = null;
        //1 获取连接
        try {
            conn = JdbcUtils.getConnection();
            //2 开启事物
            conn.setAutoCommit(false);
            //3 获取PreparedStatement
            ps = conn.prepareStatement("update ccount set money=money-? where sname=?");
            //4 使用PreparedStatement
            ps.setDouble(1,1000);
            ps.setString(2, "李四");
            ps.executeUpdate();
            System.out.println(11/0);
            ps = conn.prepareStatement("update ccount set money=money+? where sname=?");
            ps.setDouble(1,1000);
            ps.setString(2, "张三");
            ps.executeUpdate();
            // 5 提交事物
            conn.commit();
            System.out.println("转账成功");
        } catch (Exception e) {
            // 6 事物回滚
            try {
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
            System.out.println("转账失败");
        }finally{
            // 7 关闭资源
            JdbcUtils.close(conn, ps);
        }

    }
}