下载&配置

先下载官方提供的示例代码：seata-samples

代码下载下来后内部是包含了多种方式的示例，这里我们使用的是nacos + mysql + spring的方式，所以选择springcloud-nacos-seata示例进行测试，在项目跟路径下maven的配置文件pom.xml下的modules中将springcloud-nacos-seata的注释去除。

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......
<modules>
    ......
    <module>springcloud-nacos-seata</module>
    ......
</modules>
......

修改order-service和stock-service各自application.properties中的配置信息为自己的信息。

建表

数据库自己随便建一个，名称与上面项目中数据库配置信息要对应

我们这里采用AT模式，所以需要建立UNDO_LOG表，其目的是用于二阶段中的回滚。

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-- 注意此处0.3.0+ 增加唯一索引 ux_undo_log
CREATE TABLE `undo_log` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `branch_id` bigint(20) NOT NULL,
  `xid` varchar(100) NOT NULL,
  `context` varchar(128) NOT NULL,
  `rollback_info` longblob NOT NULL,
  `log_status` int(11) NOT NULL,
  `log_created` datetime NOT NULL,
  `log_modified` datetime NOT NULL,
  `ext` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

另外两个示例需要的业务表

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DROP TABLE IF EXISTS `storage_tbl`;
CREATE TABLE `storage_tbl` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `commodity_code` varchar(255) DEFAULT NULL,
  `count` int(11) DEFAULT 0,
  PRIMARY KEY (`id`),
  UNIQUE KEY (`commodity_code`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


DROP TABLE IF EXISTS `order_tbl`;
CREATE TABLE `order_tbl` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` varchar(255) DEFAULT NULL,
  `commodity_code` varchar(255) DEFAULT NULL,
  `count` int(11) DEFAULT 0,
  `money` int(11) DEFAULT 0,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

启动

分别运行StockServiceApplication与OrderServiceApplication，如果启动遇到下面这个异常，那么在启动参数中添加--add-opens=java.base/java.lang=ALL-UNNAMED

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2022-09-20 16:32:29.936 ERROR 38453 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'globalTransactionScanner' defined in class path resource [io/seata/spring/boot/autoconfigure/SeataAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [io.seata.spring.annotation.GlobalTransactionScanner]: Factory method 'globalTransactionScanner' threw exception; nested exception is java.lang.ExceptionInInitializerError
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:657) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:637) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1176) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:229) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:723) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:405) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.12.RELEASE.jar:2.2.12.RELEASE]
    at com.work.stock.StockServiceApplication.main(StockServiceApplication.java:30) ~[classes/:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [io.seata.spring.annotation.GlobalTransactionScanner]: Factory method 'globalTransactionScanner' threw exception; nested exception is java.lang.ExceptionInInitializerError
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    ... 19 common frames omitted
Caused by: java.lang.ExceptionInInitializerError: null
    at net.sf.cglib.core.KeyFactory$Generator.generateClass(KeyFactory.java:166) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.KeyFactory$Generator.create(KeyFactory.java:144) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:116) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:108) ~[cglib-3.1.jar:na]
    at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:104) ~[cglib-3.1.jar:na]
    at net.sf.cglib.proxy.Enhancer.<clinit>(Enhancer.java:69) ~[cglib-3.1.jar:na]
    at io.seata.config.ConfigurationCache.proxy(ConfigurationCache.java:88) ~[seata-all-1.4.2.jar:1.4.2]
    at io.seata.config.ConfigurationFactory.buildConfiguration(ConfigurationFactory.java:136) ~[seata-all-1.4.2.jar:1.4.2]
    at io.seata.config.ConfigurationFactory.getInstance(ConfigurationFactory.java:94) ~[seata-all-1.4.2.jar:1.4.2]
    at io.seata.spring.annotation.GlobalTransactionScanner.<init>(GlobalTransactionScanner.java:87) ~[seata-all-1.4.2.jar:1.4.2]
    at io.seata.spring.annotation.GlobalTransactionScanner.<init>(GlobalTransactionScanner.java:143) ~[seata-all-1.4.2.jar:1.4.2]
    at io.seata.spring.boot.autoconfigure.SeataAutoConfiguration.globalTransactionScanner(SeataAutoConfiguration.java:55) ~[seata-spring-boot-starter-1.4.2.jar:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.12.RELEASE.jar:5.2.12.RELEASE]
    ... 20 common frames omitted
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @635eaaf1
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354) ~[na:na]
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297) ~[na:na]
    at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199) ~[na:na]
    at java.base/java.lang.reflect.Method.setAccessible(Method.java:193) ~[na:na]
    at net.sf.cglib.core.ReflectUtils$2.run(ReflectUtils.java:56) ~[cglib-3.1.jar:na]
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:318) ~[na:na]
    at net.sf.cglib.core.ReflectUtils.<clinit>(ReflectUtils.java:46) ~[cglib-3.1.jar:na]
    ... 39 common frames omitted

验证分布式事务

order-service中OrderService类提供了一个业务方法，里面包括了订单和库存的操作，这个业务方法上有一个@GlobalTransactional，加上这个注解表示该方法开启分布式事务，就是这么简单，这里它就是分布式事务的发起者，也叫做TM

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/**
 * 下单：创建订单、减库存，涉及到两个服务
 *
 * @param userId
 * @param commodityCode
 * @param count
 */
@GlobalTransactional
@Transactional(rollbackFor = Exception.class)
public void placeOrder(String userId, String commodityCode, Integer count) {
    BigDecimal orderMoney = new BigDecimal(count).multiply(new BigDecimal(5));
    Order order = new Order().setUserId(userId).setCommodityCode(commodityCode).setCount(count).setMoney(
        orderMoney);
    orderDAO.insert(order);
    stockFeignClient.deduct(commodityCode, count);
}

上面stockFeignClient.deduct(commodityCode, count)这行代码调用的是stock-service服务下StockService类下的deduct方法，这里它是分布式事务的参与者，也叫做RM

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/**
 * 减库存
 *
 * @param commodityCode
 * @param count
 */
@Transactional(rollbackFor = Exception.class)
public void deduct(String commodityCode, int count) {
    if (commodityCode.equals("product-2")) {
        throw new RuntimeException("异常:模拟业务异常:stock branch exception");
    }

    QueryWrapper<Stock> wrapper = new QueryWrapper<>();
    wrapper.setEntity(new Stock().setCommodityCode(commodityCode));
    Stock stock = stockDAO.selectOne(wrapper);
    stock.setCount(stock.getCount() - count);

    stockDAO.updateById(stock);
}

从代码就可以看出只要commodityCode为product-2就会抛出异常，然后就会进行全局回滚，调用OrderController提供的placeOrderCommit和placeOrderRollback分别进行提交和回滚操作，当然如果你掉用的placeOrderCommit也回滚了，那可能是你数据库stock_tbl表中没有加对应的数据。

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