Seata源码—2.seata-samples项目介绍

大纲

1.seata-samples的配置文件和启动类

2.seata-samples业务服务启动时的核心工作

3.seata-samples库存服务的连接池配置

4.Seata对数据库连接池代理配置的分析

5.Dubbo RPC通信过程中传递全局事务XID

6.Seata跟Dubbo整合的Filter(基于SPI机制)

7.seata-samples的AT事务例子原理流程

8.Seata核心配置文件file.conf的内容介绍

1.seata-samples的配置文件和启动类

(1)seata-samples的测试步骤

(2)seata-samples用户服务的配置和启动类

(3)seata-samples库存服务的配置和启动类

(4)seata-samples订单服务的配置和启动类

(5)seata-samples业务服务的配置和启动类

示例仓库：

https://github.com/seata/seata-samples

示例代码的模块ID：seata-samples-dubbo

(1)seata-samples的测试步骤

步骤一：启动DubboAccountServiceStarter

步骤二：启动DubboStorageServiceStarter

步骤三：启动DubboOrderServiceStarter

步骤四：运行DubboBusinessTester

(2)seata-samples用户服务的配置和启动类

dubbo-account-service.xml配置文件：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <!-- 把jdbc.properties文件里的配置加载进来 -->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:jdbc.properties"/>
    </bean>

    <!-- 将配置文件里的值注入到库存服务的数据库连接池accountDataSource中 -->
    <bean name="accountDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="url" value="${jdbc.account.url}"/>
        <property name="username" value="${jdbc.account.username}"/>
        <property name="password" value="${jdbc.account.password}"/>
        <property name="driverClassName" value="${jdbc.account.driver}"/>
        <property name="initialSize" value="0"/>
        <property name="maxActive" value="180"/>
        <property name="minIdle" value="0"/>
        <property name="maxWait" value="60000"/>
        <property name="validationQuery" value="Select 'x' from DUAL"/>
        <property name="testOnBorrow" value="false"/>
        <property name="testOnReturn" value="false"/>
        <property name="testWhileIdle" value="true"/>
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>
        <property name="minEvictableIdleTimeMillis" value="25200000"/>
        <property name="removeAbandoned" value="true"/>
        <property name="removeAbandonedTimeout" value="1800"/>
        <property name="logAbandoned" value="true"/>
        <property name="filters" value="mergeStat"/>
    </bean>

    <!-- 创建数据库连接池代理，通过DataSourceProxy代理accountDataSourceProxy数据库连接池 -->
    <bean id="accountDataSourceProxy" class="io.seata.rm.datasource.DataSourceProxy">
        <constructor-arg ref="accountDataSource"/>
    </bean>

    <!-- 将数据库连接池代理accountDataSourceProxy注入到JdbcTemplate数据库操作组件中-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="accountDataSourceProxy"/>
    </bean>

    <dubbo:application name="dubbo-demo-account-service">
        <dubbo:parameter key="qos.enable" value="false"/>
    </dubbo:application>
    <dubbo:registry address="zookeeper://localhost:2181" />
    <dubbo:protocol name="dubbo" port="20881"/>
    <dubbo:service interface="io.seata.samples.dubbo.service.AccountService" ref="service" timeout="10000"/>

    <!-- 将JdbcTemplate数据库操作组件注入到AccountServiceImpl中 -->
    <bean id="service" class="io.seata.samples.dubbo.service.impl.AccountServiceImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate"/>
    </bean>

    <!-- 全局事务注解扫描组件 -->
    <bean class="io.seata.spring.annotation.GlobalTransactionScanner">
        <constructor-arg value="dubbo-demo-account-service"/>
        <constructor-arg value="my_test_tx_group"/>
    </bean>
</beans>

启动类：

public class DubboAccountServiceStarter {
    //Account service is ready. A buyer register an account: U100001 on my e-commerce platform
    public static void main(String[] args) {
        ClassPathXmlApplicationContext accountContext = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-account-service.xml"}
        );
        accountContext.getBean("service");
        JdbcTemplate accountJdbcTemplate = (JdbcTemplate)accountContext.getBean("jdbcTemplate");
        accountJdbcTemplate.update("delete from account_tbl where user_id = 'U100001'");
        accountJdbcTemplate.update("insert into account_tbl(user_id, money) values ('U100001', 999)");
        new ApplicationKeeper(accountContext).keep();
    }
}

//The type Application keeper.
public class ApplicationKeeper {
    private static final Logger LOGGER = LoggerFactory.getLogger(ApplicationKeeper.class);
    private final ReentrantLock LOCK = new ReentrantLock();
    private final Condition STOP = LOCK.newCondition();

    //Instantiates a new Application keeper.
    public ApplicationKeeper(AbstractApplicationContext applicationContext) {
        addShutdownHook(applicationContext);
    }

    private void addShutdownHook(final AbstractApplicationContext applicationContext) {
        Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    applicationContext.close();
                    LOGGER.info("ApplicationContext " + applicationContext + " is closed.");
                } catch (Exception e) {
                    LOGGER.error("Failed to close ApplicationContext", e);
                }

                LOCK.lock();
                try {
                    STOP.signal();
                } finally {
                    LOCK.unlock();
                }
            }
        }));
    }

    public void keep() {
        LOCK.lock();
        try {
            LOGGER.info("Application is keep running ... ");
            STOP.await();
        } catch (InterruptedException e) {
            LOGGER.error("ApplicationKeeper.keep() is interrupted by InterruptedException!", e);
        } finally {
            LOCK.unlock();
        }
    }
}

(3)seata-samples库存服务的配置和启动类

dubbo-stock-service.xml配置文件：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <!-- 把jdbc.properties文件里的配置加载进来 -->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:jdbc.properties"/>
    </bean>

    <!-- 将配置文件里的值注入到库存服务的数据库连接池stockDataSource中 -->
    <bean name="stockDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="url" value="${jdbc.stock.url}"/>
        <property name="username" value="${jdbc.stock.username}"/>
        <property name="password" value="${jdbc.stock.password}"/>
        <property name="driverClassName" value="${jdbc.stock.driver}"/>
        <property name="initialSize" value="0"/>
        <property name="maxActive" value="180"/>
        <property name="minIdle" value="0"/>
        <property name="maxWait" value="60000"/>
        <property name="validationQuery" value="Select 'x' from DUAL"/>
        <property name="testOnBorrow" value="false"/>
        <property name="testOnReturn" value="false"/>
        <property name="testWhileIdle" value="true"/>
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>
        <property name="minEvictableIdleTimeMillis" value="25200000"/>
        <property name="removeAbandoned" value="true"/>
        <property name="removeAbandonedTimeout" value="1800"/>
        <property name="logAbandoned" value="true"/>
        <property name="filters" value="mergeStat"/>
    </bean>

    <!-- 创建数据库连接池代理，通过DataSourceProxy代理stockDataSource数据库连接池 -->
    <bean id="stockDataSourceProxy" class="io.seata.rm.datasource.DataSourceProxy">
        <constructor-arg ref="stockDataSource"/>
    </bean>

    <!-- 将数据库连接池代理stockDataSourceProxy注入到JdbcTemplate数据库操作组件中-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="stockDataSourceProxy"/>
    </bean>

    <dubbo:application name="dubbo-demo-stock-service">
        <dubbo:parameter key="qos.enable" value="false"/>
    </dubbo:application>
    <dubbo:registry address="zookeeper://localhost:2181" />
    <dubbo:protocol name="dubbo" port="20882"/>
    <dubbo:service interface="io.seata.samples.dubbo.service.StockService" ref="service" timeout="10000"/>

    <!-- 将JdbcTemplate数据库操作组件注入到StockServiceImpl中 -->
    <bean id="service" class="io.seata.samples.dubbo.service.impl.StockServiceImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate"/>
    </bean>

    <!-- 全局事务注解扫描组件 -->
    <bean class="io.seata.spring.annotation.GlobalTransactionScanner">
        <constructor-arg value="dubbo-demo-stock-service"/>
        <constructor-arg value="my_test_tx_group"/>
    </bean>
</beans>

启动类：

//The type Dubbo stock service starter.
public class DubboStockServiceStarter {
    //Stock service is ready. A seller add 100 stock to a sku: C00321
    public static void main(String[] args) {
        ClassPathXmlApplicationContext stockContext = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-stock-service.xml"}
        );
        stockContext.getBean("service");
        JdbcTemplate stockJdbcTemplate = (JdbcTemplate)stockContext.getBean("jdbcTemplate");
        stockJdbcTemplate.update("delete from stock_tbl where commodity_code = 'C00321'");
        stockJdbcTemplate.update("insert into stock_tbl(commodity_code, count) values ('C00321', 100)");
        new ApplicationKeeper(stockContext).keep();
    }
}

(4)seata-samples订单服务的配置和启动类

dubbo-order-service.xml配置文件：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <!-- 把jdbc.properties文件里的配置加载进来 -->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:jdbc.properties"/>
    </bean>

    <!-- 将配置文件里的值注入到库存服务的数据库连接池orderDataSource中 -->
    <bean name="orderDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="url" value="${jdbc.order.url}"/>
        <property name="username" value="${jdbc.order.username}"/>
        <property name="password" value="${jdbc.order.password}"/>
        <property name="driverClassName" value="${jdbc.order.driver}"/>
        <property name="initialSize" value="0"/>
        <property name="maxActive" value="180"/>
        <property name="minIdle" value="0"/>
        <property name="maxWait" value="60000"/>
        <property name="validationQuery" value="Select 'x' from DUAL"/>
        <property name="testOnBorrow" value="false"/>
        <property name="testOnReturn" value="false"/>
        <property name="testWhileIdle" value="true"/>
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>
        <property name="minEvictableIdleTimeMillis" value="25200000"/>
        <property name="removeAbandoned" value="true"/>
        <property name="removeAbandonedTimeout" value="1800"/>
        <property name="logAbandoned" value="true"/>
        <property name="filters" value="mergeStat"/>
    </bean>

    <!-- 创建数据库连接池代理，通过DataSourceProxy代理stockDataSource数据库连接池 -->
    <bean id="orderDataSourceProxy" class="io.seata.rm.datasource.DataSourceProxy">
        <constructor-arg ref="orderDataSource"/>
    </bean>

    <!-- 将数据库连接池代理orderDataSourceProxy注入到JdbcTemplate数据库操作组件中-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="orderDataSourceProxy"/>
    </bean>

    <dubbo:application name="dubbo-demo-order-service">
        <dubbo:parameter key="qos.enable" value="false"/>
    </dubbo:application>
    <dubbo:registry address="zookeeper://localhost:2181" />
    <dubbo:protocol name="dubbo" port="20883"/>
    <dubbo:service interface="io.seata.samples.dubbo.service.OrderService" ref="service" timeout="10000"/>
    <dubbo:reference id="accountService" check="false" interface="io.seata.samples.dubbo.service.AccountService"/>

    <!-- 将JdbcTemplate数据库操作组件注入到OrderServiceImpl中 -->
    <bean id="service" class="io.seata.samples.dubbo.service.impl.OrderServiceImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate"/>
        <property name="accountService" ref="accountService"/>
    </bean>

    <!-- 全局事务注解扫描组件 -->
    <bean class="io.seata.spring.annotation.GlobalTransactionScanner">
        <constructor-arg value="dubbo-demo-order-service"/>
        <constructor-arg value="my_test_tx_group"/>
    </bean>
</beans>

启动类：

//The type Dubbo order service starter.
public class DubboOrderServiceStarter {
    //The entry point of application.
    public static void main(String[] args) {
        //Order service is ready . Waiting for buyers to order
        ClassPathXmlApplicationContext orderContext = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-order-service.xml"}
        );
        orderContext.getBean("service");
        new ApplicationKeeper(orderContext).keep();
    }
}

(5)seata-samples业务服务的配置和启动类

dubbo-business.xml配置文件：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <dubbo:application name="dubbo-demo-app">
        <dubbo:parameter key="qos.enable" value="false"/>
        <dubbo:parameter key="qos.accept.foreign.ip" value="false"/>
        <dubbo:parameter key="qos.port" value="33333"/>
    </dubbo:application>
    <dubbo:registry address="zookeeper://localhost:2181" />
    <dubbo:reference id="orderService" check="false" interface="io.seata.samples.dubbo.service.OrderService"/>
    <dubbo:reference id="stockService" check="false" interface="io.seata.samples.dubbo.service.StockService"/>

    <bean id="business" class="io.seata.samples.dubbo.service.impl.BusinessServiceImpl">
        <property name="orderService" ref="orderService"/>
        <property name="stockService" ref="stockService"/>
    </bean>

    <!-- 全局事务注解扫描组件 -->
    <bean class="io.seata.spring.annotation.GlobalTransactionScanner">
        <constructor-arg value="dubbo-demo-app"/>
        <constructor-arg value="my_test_tx_group"/>
    </bean>
</beans>

启动类：

//The type Dubbo business tester.
public class DubboBusinessTester {
    //The entry point of application.
    public static void main(String[] args) {
        //The whole e-commerce platform is ready, The buyer(U100001) create an order on the sku(C00321) , the count is 2
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-business.xml"}
        );
        //模拟调用下单接口
        final BusinessService business = (BusinessService)context.getBean("business");
        business.purchase("U100001", "C00321", 2);
    }
}

2.seata-samples业务服务启动时的核心工作

BusinessService业务服务启动时，会创建两个服务接口的动态代理。一个是OrderService订单服务接口的Dubbo动态代理，另一个是StockService库存服务接口的Dubbo动态代理。BusinessService业务服务的下单接口会添加@GlobalTransaction注解，通过@GlobalTransaction注解开启一个分布式事务，Seata的内核组件GlobalTransactionScanner就会扫描到这个注解。

//The type Dubbo business tester.
public class DubboBusinessTester {
    //The entry point of application.
    public static void main(String[] args) {
        //The whole e-commerce platform is ready , The buyer(U100001) create an order on the sku(C00321) , the count is 2
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-business.xml"}
        );
        //模拟调用下单接口
        final BusinessService business = (BusinessService)context.getBean("business");
        business.purchase("U100001", "C00321", 2);
    }
}

public class BusinessServiceImpl implements BusinessService {
    private static final Logger LOGGER = LoggerFactory.getLogger(BusinessService.class);
    private StockService stockService;
    private OrderService orderService;
    private Random random = new Random();

    @Override
    @GlobalTransactional(timeoutMills = 300000, name = "dubbo-demo-tx")//分布式事务如果5分钟还没跑完，就是超时
    public void purchase(String userId, String commodityCode, int orderCount) {
        LOGGER.info("purchase begin ... xid: " + RootContext.getXID());
        stockService.deduct(commodityCode, orderCount);
        orderService.create(userId, commodityCode, orderCount);
        if (random.nextBoolean()) {
            throw new RuntimeException("random exception mock!");
        }
    }

    //Sets stock service.
    public void setStockService(StockService stockService) {
        this.stockService = stockService;
    }

    //Sets order service.
    public void setOrderService(OrderService orderService) {
        this.orderService = orderService;
    }
}

3.seata-samples库存服务的连接池配置

首先会把jdbc.properties文件里的配置加载进来，然后将配置配置的值注入到库存服务的数据库连接池，接着通过Seata的DataSourceProxy对数据库连接池进行代理。

一.启动类

//The type Dubbo stock service starter.
public class DubboStockServiceStarter {
    //Stock service is ready. A seller add 100 stock to a sku: C00321
    public static void main(String[] args) {
        ClassPathXmlApplicationContext stockContext = new ClassPathXmlApplicationContext(
            new String[] {"spring/dubbo-stock-service.xml"}
        );
        stockContext.getBean("service");
        JdbcTemplate stockJdbcTemplate = (JdbcTemplate)stockContext.getBean("jdbcTemplate");
        stockJdbcTemplate.update("delete from stock_tbl where commodity_code = 'C00321'");
        stockJdbcTemplate.update("insert into stock_tbl(commodity_code, count) values ('C00321', 100)");
        new ApplicationKeeper(stockContext).keep();
    }
}

二.dubbo-stock-service.xml文件

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <!-- 把jdbc.properties文件里的配置加载进来 -->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:jdbc.properties"/>
    </bean>

    <!-- 将配置文件里的值注入到库存服务的数据库连接池stockDataSource中 -->
    <bean name="stockDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="url" value="${jdbc.stock.url}"/>
        <property name="username" value="${jdbc.stock.username}"/>
        <property name="password" value="${jdbc.stock.password}"/>
        <property name="driverClassName" value="${jdbc.stock.driver}"/>
        <property name="initialSize" value="0"/>
        <property name="maxActive" value="180"/>
        <property name="minIdle" value="0"/>
        <property name="maxWait" value="60000"/>
        <property name="validationQuery" value="Select 'x' from DUAL"/>
        <property name="testOnBorrow" value="false"/>
        <property name="testOnReturn" value="false"/>
        <property name="testWhileIdle" value="true"/>
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>
        <property name="minEvictableIdleTimeMillis" value="25200000"/>
        <property name="removeAbandoned" value="true"/>
        <property name="removeAbandonedTimeout" value="1800"/>
        <property name="logAbandoned" value="true"/>
        <property name="filters" value="mergeStat"/>
    </bean>

    <!-- 创建数据库连接池代理，通过DataSourceProxy代理stockDataSource数据库连接池 -->
    <bean id="stockDataSourceProxy" class="io.seata.rm.datasource.DataSourceProxy">
        <constructor-arg ref="stockDataSource"/>
    </bean>

    <!-- 将数据库连接池代理stockDataSourceProxy注入到JdbcTemplate数据库操作组件中-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="stockDataSourceProxy"/>
    </bean>
    <dubbo:application name="dubbo-demo-stock-service">
        <dubbo:parameter key="qos.enable" value="false"/>
    </dubbo:application>
    <dubbo:registry address="zookeeper://localhost:2181" />
    <dubbo:protocol name="dubbo" port="20882"/>
    <dubbo:service interface="io.seata.samples.dubbo.service.StockService" ref="service" timeout="10000"/>

    <!-- 将JdbcTemplate数据库操作组件注入到StockServiceImpl中 -->
    <bean id="service" class="io.seata.samples.dubbo.service.impl.StockServiceImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate"/>
    </bean>

    <!-- 全局事务注解扫描组件 -->
    <bean class="io.seata.spring.annotation.GlobalTransactionScanner">
        <constructor-arg value="dubbo-demo-stock-service"/>
        <constructor-arg value="my_test_tx_group"/>
    </bean>
</beans>

三.jdbc.properties文件文件

jdbc.account.url=jdbc:mysql://localhost:3306/seata
jdbc.account.username=root
jdbc.account.password=123456
jdbc.account.driver=com.mysql.jdbc.Driver
# stock db config
jdbc.stock.url=jdbc:mysql://localhost:3306/seata
jdbc.stock.username=root
jdbc.stock.password=123456
jdbc.stock.driver=com.mysql.jdbc.Driver
# order db config
jdbc.order.url=jdbc:mysql://localhost:3306/seata
jdbc.order.username=root
jdbc.order.password=123456
jdbc.order.driver=com.mysql.jdbc.Driver

4.Seata对数据库连接池代理配置的分析

数据库连接池代理DataSourceProxy，会注入到JdbcTemplate数据库操作组件中。这样库存或者订单服务就可以通过Spring数据库操作组件JdbcTemplate，向Seata数据库连接池代理DataSourceProxy获取一个数据库连接。然后通过数据库连接，把SQL请求发送给MySQL进行处理。

5.Dubbo RPC通信过程中传递全局事务XID

BusinessService对StockService进行RPC调用时，会传递全局事务XID。StockService便可以根据RootContext.getXID()获取到全局事务XID。

public class BusinessServiceImpl implements BusinessService {
    private static final Logger LOGGER = LoggerFactory.getLogger(BusinessService.class);
    private StockService stockService;
    private OrderService orderService;
    private Random random = new Random();

    @Override
    @GlobalTransactional(timeoutMills = 300000, name = "dubbo-demo-tx")//分布式事务如果5分钟还没跑完，就是超时
    public void purchase(String userId, String commodityCode, int orderCount) {
        LOGGER.info("purchase begin ... xid: " + RootContext.getXID());
        stockService.deduct(commodityCode, orderCount);
        orderService.create(userId, commodityCode, orderCount);
        if (random.nextBoolean()) {
            throw new RuntimeException("random exception mock!");
        }
    }
    ...
}

public class StockServiceImpl implements StockService {
    private static final Logger LOGGER = LoggerFactory.getLogger(StockService.class);
    private JdbcTemplate jdbcTemplate;

    @Override
    public void deduct(String commodityCode, int count) {
        LOGGER.info("Stock Service Begin ... xid: " + RootContext.getXID());
        LOGGER.info("Deducting inventory SQL: update stock_tbl set count = count - {} where commodity_code = {}", count, commodityCode);

        jdbcTemplate.update("update stock_tbl set count = count - ? where commodity_code = ?", new Object[] {count, commodityCode});
        LOGGER.info("Stock Service End ... ");
    }
    ...
}

6.Seata跟Dubbo整合的Filter(基于SPI机制)

Seata与Dubbo整合的Filter过滤器ApacheDubboTransactionPropagationFilter会将向SeataServer注册的全局事务xid，设置到RootContext中。

7.seata-samples的AT事务例子原理流程

8.Seata核心配置文件file.conf的内容介绍

# Seata网络通信相关的配置
transport {
    # 网络通信的类型是TCP
    type = "TCP"
    # 网络服务端使用NIO模式
    server = "NIO"
    # 是否开启心跳
    heartbeat = true
    # 是否允许Seata的客户端批量发送请求
    enableClientBatchSendRequest = true
    # 使用Netty进行网络通信时的线程配置
    threadFactory {
        bossThreadPrefix = "NettyBoss"
        workerThreadPrefix = "NettyServerNIOWorker"
        serverExecutorThread-prefix = "NettyServerBizHandler"
        shareBossWorker = false
        clientSelectorThreadPrefix = "NettyClientSelector"
        clientSelectorThreadSize = 1
        clientWorkerThreadPrefix = "NettyClientWorkerThread"
        # 用来监听和建立网络连接的Boss线程的数量
        bossThreadSize = 1
        # 默认的Worker线程数量是8
        workerThreadSize = "default"
    }
    shutdown {
        # 销毁服务端的时候的等待时间是多少秒
        wait = 3
    }
    # 序列化类型是Seata
    serialization = "seata"
    # 是否开启压缩
    compressor = "none"
}

# Seata服务端相关的配置
service {
    # 分布式事务的分组
    vgroupMapping.my_test_tx_group = "default"
    # only support when registry.type=file, please don't set multiple addresses
    default.grouplist = "127.0.0.1:8091"
    # 是否开启降级
    enableDegrade = false
    # 是否禁用全局事务
    disableGlobalTransaction = false
}

# Seata客户端相关的配置
client {
    # 数据源管理组件的配置
    rm {
        # 异步提交缓冲区的大小
        asyncCommitBufferLimit = 10000
        # 锁相关的配置：重试间隔、重试次数、回滚冲突处理
        lock {
            retryInterval = 10
            retryTimes = 30
            retryPolicyBranchRollbackOnConflict = true
        }
        reportRetryCount = 5
        tableMetaCheckEnable = false
        reportSuccessEnable = false
    }
    # 事务管理组件的配置
    tm {
        commitRetryCount = 5
        rollbackRetryCount = 5
    }
    # 回滚日志的配置
    undo {
        dataValidation = true
        logSerialization = "jackson"
        logTable = "undo_log"
    }
    # log日志的配置
    log {
        exceptionRate = 100
    }
}