事务练习-购买图书

事务练习-购买图书

package jdbc;

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

public class BookStore {
	public static boolean buy(int userid,int bookid) {
		String update1="update bookstore set count=count-1 where bookid=?";
		String update2="update sys_user set remain=remain-(select price from book where bookid=?) where userid=?";
		String query1="select count from bookstore where bookid=?";
		String query2="select remain from sys_user where userid=?";
		Connection conn=jdbcUtil.getConnection();//jdbcUtil为jdbc连接数据库封装
		try(PreparedStatement ps_u1=conn.prepareStatement(update1);
				PreparedStatement ps_u2=conn.prepareStatement(update2);
				PreparedStatement ps_q1=conn.prepareStatement(query1);
				PreparedStatement ps_q2=conn.prepareStatement(query2);
				
				){
			conn.setAutoCommit(false);//关闭自动提交
			
			//更新
			ps_u1.setInt(1, bookid);
			ps_u1.execute();
			ps_u2.setInt(1, bookid);
			ps_u2.setInt(2,userid);
			ps_u2.execute();
			
			//查询
			ps_q1.setInt(1, bookid);
			ResultSet rs1=ps_q1.executeQuery();
			rs1.next();
			int store=rs1.getInt(1);
			
			ps_q2.setInt(1, userid);
			ResultSet rs2=ps_q1.executeQuery();
			rs2.next();
			int remain=rs2.getInt(1);
			
			if(remain>0 && store>0) {
				conn.commit();
			}else {
				throw new Exception("库存或余额不足");
			}
			System.out.println("购买成功，剩余余额"+remain+"，库存"+store);
			return true;
			
		} catch (Exception e) {
			e.printStackTrace();
			try {
				conn.rollback();
			} catch (SQLException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
			// TODO: handle exception
		}finally {
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return false;
		
	}
	public static void main(String[] args) {
		buy(2,1);
	}
}

sys_user表

bookstore表

book表