@Transactional注解属性(2)

本文主要介绍了@Transactional注解的propagation属性,该属性指定事务传播行为。详细讲解了两种传播行为:REQUIRED默认在现有事务内运行,否则启动新事务;REQUIRES_NEW必须启动新事务,挂起现有事务。通过买书场景测试类分析了不同传播行为下事务的运行和回滚情况。

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@Transactional注解属性(2)


 文章目录

      4、propagation


propagation:指定事务传播行为,一个事务方法被另一个事务方法调用时,必须指定事务应该如何传播,例如:方法可能继承在现有事务中运行,也可能开启一个新事物。以下列举了两个事务的传播行为:


REQUIRED:默认值,如果有事务在运行,当前的方法就在这个事务内运行,否则,就启动一个新的事务,并在自己的事务内运行

测试类:

        场景:一个人(id为aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa)的钱包有100元,它想买两类书,第一类id为a2f39533-659f-42ca-af91-c688a83f6e49,数量为1本,单价为10元,该书库存为10本;第二类id为4c37672a-653c-4cc8-9ab5-ee0c614c7425,数量为10,单价为10元,该书库存为10本;

package com.jd.test;

import java.util.*;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jd.car.ICarService;
import com.jd.car.imp.CarService;

public class Test {
	
	public static void main(String[] args) {
		ClassPathXmlApplicationContext application = new ClassPathXmlApplicationContext("application.xml");
		ICarService carService = application.getBean(CarService.class);
		String userId = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";
		Map<String,Integer> commodities = new HashMap<String,Integer>();
		commodities.put("a2f39533-659f-42ca-af91-c688a83f6e49",1);
		commodities.put("4c37672a-653c-4cc8-9ab5-ee0c614c7425",10);
		carService.batch(userId, commodities);
		application.close();
	}
}

CarService类

package com.jd.car.imp;

import java.util.*;
import java.util.Map.Entry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.jd.car.ICarService;
import com.jd.coupon.ICouponService;

@Service
public class CarService implements ICarService {

	@Autowired
	private ICouponService couponService;

	//购物车购买
	@Override
	@Transactional
	public boolean batch(String userId,Map<String,Integer> commodities) {
		Set<Entry<String, Integer>> set = commodities.entrySet();
		for (Entry<String, Integer> commodity : set) {
			String bookId = commodity.getKey();
			int count = commodity.getValue();
			System.out.println(bookId+","+count);
			couponService.insert(userId,bookId, count);
		}
		return true;
	}
}

CouponService类

package com.jd.coupon.imp;

import java.util.*;
import java.util.Map.Entry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import com.jd.book.IBookDao;
import com.jd.coupon.ICouponDao;
import com.jd.coupon.ICouponService;
import com.jd.money.IMoneyDao;
import com.jd.vo.Coupon;

@Service
public class CouponService implements ICouponService {

	@Autowired
	private IBookDao bookDao;
	@Autowired
	private IMoneyDao moneyDao;
	@Autowired
	private ICouponDao couponDao;
	
	//立即购买
	@Override
	@Transactional/*(propagation=Propagation.REQUIRED)*/
	public boolean insert(String userId,String bookId, int count){
		
		if(bookDao.enough(bookId, count)) {//书籍足够
			//书籍表库存递减
			bookDao.update(bookId, count);
		}
		double price = bookDao.getPrice(bookId);
		double total = price*count;
		if(moneyDao.enough(userId, total)) {//余额足够
			//订单表添加数据
			Coupon coupon = new Coupon();
			coupon.setId(UUID.randomUUID().toString());
			coupon.setUserId(userId);
			coupon.setBookId(bookId);
			coupon.setTotal(total);
			couponDao.insert(coupon);
			//钱包表递减
			moneyDao.update(userId, total);
		}
		return true;
	}
}

分析:

       事务方法insert被另一个事务方法batch调用时,事务方法insert默认在batch方法的事务内运行,即insert方法和batch方法在同一个事务中(相当于修饰insert方法的@Transactional注解中添加了“propagation=Propagation.REQUIRED”属性),因此结算第二类书籍时钱包钱不够,insert方法抛出了异常以至于insert方法和batch方法所在的事务进行了回滚,最终导致第一类书籍的结算也时效,即书籍表、money表不会发生变化,且也不会生成订单,如下图所示:

book表数量依旧不变

money表账户余额依旧不变

coupon表不会生成订单

注意: 当删掉iCouponService类中insert方法的@Transactional/*(propagation=Propagation.REQUIRED)*/注解时,如下图所示:

package com.jd.coupon.imp;

import java.util.*;
import java.util.Map.Entry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import com.jd.book.IBookDao;
import com.jd.coupon.ICouponDao;
import com.jd.coupon.ICouponService;
import com.jd.money.IMoneyDao;
import com.jd.vo.Coupon;

@Service
public class CouponService implements ICouponService {

	@Autowired
	private IBookDao bookDao;
	@Autowired
	private IMoneyDao moneyDao;
	@Autowired
	private ICouponDao couponDao;
	
	//立即购买
	@Override
	public boolean insert(String userId,String bookId, int count){
		
		if(bookDao.enough(bookId, count)) {//书籍足够
			//书籍表库存递减
			bookDao.update(bookId, count);
		}
		double price = bookDao.getPrice(bookId);
		double total = price*count;
		if(moneyDao.enough(userId, total)) {//余额足够
			//订单表添加数据
			Coupon coupon = new Coupon();
			coupon.setId(UUID.randomUUID().toString());
			coupon.setUserId(userId);
			coupon.setBookId(bookId);
			coupon.setTotal(total);
			couponDao.insert(coupon);
			//钱包表递减
			moneyDao.update(userId, total);
		}
		return true;
	}
}

此时如果购物车的batch方法处于事务中,虽然insert方法没有加事务注解,但在batch方法中被调用,因此和batch方法处于同一个事务中,也会事务回滚,但此时只有batch这一个事务,因此该现象不是事务的传播行为


REQUIRES_NEW:当前方法必须启动新事务,并在它自己的事务内运行,如果有事务在运行,则把当前事务挂起,直到新的事务提交或者回滚才恢复执行

测试类:

              场景:一个人(id为aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa)的钱包有100元,它想买两类书,第一类id为a2f39533-659f-42ca-af91-c688a83f6e49,数量为1本,单价为10元,该书库存为10本;第二类id为4c37672a-653c-4cc8-9ab5-ee0c614c7425,数量为10,单价为10元,该书库存为10本;

package com.jd.test;

import java.util.*;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jd.car.ICarService;
import com.jd.car.imp.CarService;

public class Test {
	
	public static void main(String[] args) {
		ClassPathXmlApplicationContext application = new ClassPathXmlApplicationContext("application.xml");
		ICarService carService = application.getBean(CarService.class);
		String userId = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";
		Map<String,Integer> commodities = new HashMap<String,Integer>();
		commodities.put("a2f39533-659f-42ca-af91-c688a83f6e49",1);
		commodities.put("4c37672a-653c-4cc8-9ab5-ee0c614c7425",10);
		carService.batch(userId, commodities);
		application.close();
	}
}

CarService类

package com.jd.car.imp;

import java.util.*;
import java.util.Map.Entry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.jd.car.ICarService;
import com.jd.coupon.ICouponService;

@Service
public class CarService implements ICarService {

	@Autowired
	private ICouponService couponService;

	//购物车购买
	@Override
	@Transactional
	public boolean batch(String userId,Map<String,Integer> commodities) {
		Set<Entry<String, Integer>> set = commodities.entrySet();
		for (Entry<String, Integer> commodity : set) {
			String bookId = commodity.getKey();
			int count = commodity.getValue();
			System.out.println(bookId+","+count);
			couponService.insert(userId,bookId, count);
		}
		return true;
	}
}

CouponService类

package com.jd.coupon.imp;

import java.util.*;
import java.util.Map.Entry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import com.jd.book.IBookDao;
import com.jd.coupon.ICouponDao;
import com.jd.coupon.ICouponService;
import com.jd.money.IMoneyDao;
import com.jd.vo.Coupon;

@Service
public class CouponService implements ICouponService {

	@Autowired
	private IBookDao bookDao;
	@Autowired
	private IMoneyDao moneyDao;
	@Autowired
	private ICouponDao couponDao;
	
	//立即购买
	@Override
	@Transactional(propagation=Propagation.REQUIRES_NEW)
	public boolean insert(String userId,String bookId, int count){
		
		if(bookDao.enough(bookId, count)) {//书籍足够
			//书籍表库存递减
			bookDao.update(bookId, count);
		}
		double price = bookDao.getPrice(bookId);
		double total = price*count;
		if(moneyDao.enough(userId, total)) {//余额足够
			//订单表添加数据
			Coupon coupon = new Coupon();
			coupon.setId(UUID.randomUUID().toString());
			coupon.setUserId(userId);
			coupon.setBookId(bookId);
			coupon.setTotal(total);
			couponDao.insert(coupon);
			//钱包表递减
			moneyDao.update(userId, total);
		}
		return true;
	}
}

分析:

              修饰insert方法的@Transactional注解中添加了“propagation=Propagation.REQUIRES_NEW”属性,则每次执行该方法时都会启动新事务,即有三个事务:第一类书籍购买为一个事务,第二类书籍购买为一个事务,batch为一个事务,所以结算第一类书籍时钱够库存也够则购买成功并提交当次事务,但结算第二类书籍时由于钱包钱不够导致支付失败,致使此次事务回滚,结果如下:

book表中,第一类书籍购买成功,数量由10变为零,第二类书籍数量依旧不变

money表中,买第一类书籍花掉100元,账户余额由100变为0

coupon表中生成订单

 

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