事务传播属性
•当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: 方法可能继续在现有事务中运行, 也可能开启一个新事务, 并在自己的事务中运行.
•事务的传播行为可以由传播属性指定. Spring 定义了 7 种类传播行为.
Spring 支持的事务传播行为
需求:
•新定义 Cashier 接口: 表示客户的结账操作
•修改数据表信息如下, 目的是用户 Tom 在结账时, 余额只能支付第一本书, 不够支付第二本书:
REQUIRED 传播行为
•当 bookService 的 purchase() 方法被另一个事务方法 checkout() 调用时, 它默认会在现有的事务内运行. 这个默认的传播行为就是 REQUIRED. 因此在 checkout() 方法的开始和终止边界内只有一个事务. 这个事务只在 checkout() 方法结束的时候被提交, 结果用户一本书都买不了
•事务传播属性可以在 @Transactional 注解的 propagation 属性中定义
REQUIRES_NEW 传播行为
•另一种常见的传播行为是 REQUIRES_NEW. 它表示该方法必须启动一个新事务, 并在自己的事务内运行. 如果有事务在运行, 就应该先挂起它.
在 Spring 2.x 事务通知中配置传播属性
•在 Spring 2.x 事务通知中, 可以像下面这样在 <tx:method> 元素中设定传播事务属性
代码示例:
1、数据库表的建立如下:
employee表
department表
2、目录结构
Spring
|——src
|——|——com.hzyc.spring.jdbc
|——|——|——employee.java
|——|——|——JdbcTest.java
|——|——application-context.xml
|——|——db.properties
2、db.properties
jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.jdbcUrl=jdbc:mysql:///spring
jdbc.user=root
jdbc.password=root
jdbc.initPoolSize=5
jdbc.maxPoolSize=10
3、application-context.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd">
<context:component-scan base-package="com.hzyc.spring"/>
<!--导入资源文件-->
<context:property-placeholder location="classpath:db.properties"/>
<!--配置 c3p0 数据源-->
<bean id="dataSource"
class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="${jdbc.driverClass}"/>
<property name="jdbcUrl" value="${jdbc.jdbcUrl}"/>
<property name="user" value="${jdbc.user}"/>
<property name="password" value="${jdbc.password}"/>
<property name="initialPoolSize" value="${jdbc.initPoolSize}"/>
<property name="maxPoolSize" value="${jdbc.maxPoolSize}"/>
</bean>
<!--配置 Spring 的 Jdbc Template-->
<bean id="jdbcTemplate"
class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
<!--
配置 NamedParameterJdbcTemplate, 该对象可以使用具名参数(具有名字)
其没有无参的构造器,必须为其构造器指定参数
-->
<bean id="namedParameterJdbcTemplate"
class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
<constructor-arg ref="dataSource"/>
</bean>
<!--配置事务管理器-->
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<!--事务注解-->
<tx:annotation-driven transaction-manager="transactionManager"/>
</beans>
BookShopDao.java
package com.hzyc.spring.jdbc.transaction;
/**
* @author xuehj2016
* @Title: BookShopDao
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 20:32
*/
public interface BookShopDao {
/**
* 根据书号获取书的单价
*/
public int getBookPriceById(String id);
/**
* 更新书的库存,使书号对应的库存 - 1
*/
public void updateBookStock(String id);
/**
* 更新用户的账户余额 : 使 username 的 balance - price
*/
public void updateUserAccount(String username, int price);
}
package com.hzyc.spring.jdbc.transaction;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: BookShopDaoImpl
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 20:39
*/
@Repository("bookShopDao")
public class BookShopDaoImpl implements BookShopDao {
@Autowired
private JdbcTemplate jdbcTemplate;
/**
* 根据书号获取书的单价
*
* @param id
*/
@Override
public int getBookPriceById(String id) {
String sql = "select price from book where id = ?";
return jdbcTemplate.queryForObject(sql, Integer.class, id);
}
/**
* 更新书的库存,使书号对应的库存 - 1
*
* @param id
*/
@Override
public void updateBookStock(String id) {
//检查书的库存是否足够,若不够,则抛出异常
String stockSql = "select stock from book_stock where id =?";
int stock = jdbcTemplate.queryForObject(stockSql, Integer.class, id);
if (stock == 0) {
throw new BookStockException("库存不足!");
}
String sql = "update book_stock set stock = stock - 1 where id =?";
jdbcTemplate.update(sql, id);
}
/**
* 更新用户的账户余额 : 使 username 的 balance - price
*
* @param username
* @param price
*/
@Override
public void updateUserAccount(String username, int price) {
//因为 MySQL 不支持检查约束
//验证用户的余额是否足够,若不够,则抛出异常
String balanceSql = "select balance from account where username =?";
int balance = jdbcTemplate.queryForObject(balanceSql, Integer.class, username);
if (balance < price) {
throw new UserAccountException("余额不足!");
}
String sql = "update account set balance = balance - ? where username =?";
jdbcTemplate.update(sql, price, username);
}
}
package com.hzyc.spring.jdbc.transaction;
/**
* @author xuehj2016
* @Title: BookShopService
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 21:22
*/
public interface BookShopService {
public void purchase(String username, String id);
}
package com.hzyc.spring.jdbc.transaction;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
/**
* @author xuehj2016
* @Title: BookShopServiceImpl
* @ProjectName Spring-3
* @Description: TODO
* @date 2018/12/21 21:24
*/
@Service("bookShopService")
public class BookShopServiceImpl implements BookShopService {
@Autowired
private BookShopDao bookShopDao;
/**
* 添加事务注解
* 1.使用 propagation 指定事务的传播行为, 即当前的事务方法被另外一个事务方法调用时
* 如何使用事务, 默认取值为 REQUIRED, 即使用调用方法的事务
* REQUIRES_NEW: 事务自己的事务, 调用的事务方法的事务被挂起.
*
* @param username
* @param id
*/
@Transactional(propagation = Propagation.REQUIRES_NEW)
@Override
public void purchase(String username, String id) {
//1.获取书的单价
int price = bookShopDao.getBookPriceById(id);
//2.更新书的库存
bookShopDao.updateBookStock(id);
//3.更新用户余额
bookShopDao.updateUserAccount(username, price);
}
}
package com.hzyc.spring.jdbc.transaction;
/**
* @author xuehj2016
* @Title: BookStockException
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 21:10
*/
public class BookStockException extends RuntimeException {
public BookStockException() {
}
public BookStockException(String message) {
super(message);
}
public BookStockException(String message, Throwable cause) {
super(message, cause);
}
public BookStockException(Throwable cause) {
super(cause);
}
public BookStockException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
super(message, cause, enableSuppression, writableStackTrace);
}
}
package com.hzyc.spring.jdbc.transaction;
import java.util.List;
/**
* @author xuehj2016
* @Title: Cashier
* @ProjectName Spring-3
* @Description: TODO
* @date 2018/12/21 23:23
*/
public interface Cashier {
public void checkout(String username, List<String> ids);
}
package com.hzyc.spring.jdbc.transaction;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
/**
* @author xuehj2016
* @Title: CashierImpl
* @ProjectName Spring-3
* @Description: TODO
* @date 2018/12/21 23:24
*/
@Service("cashier")
public class CashierImpl implements Cashier {
@Autowired
private BookShopService bookShopService;
/**
*
* @param username
* @param ids
*/
@Transactional
@Override
public void checkout(String username, List<String> ids) {
for (String id : ids) {
bookShopService.purchase(username, id);
}
}
}
package com.hzyc.spring.jdbc.transaction;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.util.Arrays;
/**
* @author xuehj2016
* @Title: SpringTransactionTest
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 20:52
*/
public class SpringTransactionTest {
private BookShopDao bookShopDao;
private BookShopService bookShopService;
private Cashier cashier;
{
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("application-context.xml");
bookShopDao = (BookShopDao) applicationContext.getBean("bookShopDao");
bookShopService = (BookShopService) applicationContext.getBean("bookShopService");
cashier = (Cashier) applicationContext.getBean("cashier");
}
@Test
public void testBookShopGetBookPriceById() {
System.out.println(bookShopDao.getBookPriceById("1001"));
}
@Test
public void testBookShopUpdateBookStock() {
bookShopDao.updateBookStock("1001");
}
@Test
public void testBookShopUpdateUserAccount() {
bookShopDao.updateUserAccount("xuehj", 50);
}
@Test
public void testBookShopService() {
bookShopService.purchase("xuehj", "1001");
}
@Test
public void testTransactionalPropagation() {
cashier.checkout("xuehj", Arrays.asList("1001", "1002"));
}
}
package com.hzyc.spring.jdbc.transaction;
/**
* @author xuehj2016
* @Title: UserAccountException
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 21:16
*/
public class UserAccountException extends RuntimeException {
public UserAccountException() {
}
public UserAccountException(String message) {
super(message);
}
public UserAccountException(String message, Throwable cause) {
super(message, cause);
}
public UserAccountException(Throwable cause) {
super(cause);
}
public UserAccountException(String message, Throwable cause, boolean enableSuppression, boolean
writableStackTrace) {
super(message, cause, enableSuppression, writableStackTrace);
}
}