8.Spring Cloud Alibaba教程：整合Seata分布式事务

概述

Seata 是一款开源的分布式事务解决方案，致力于提供高性能和简单易用的分布式事务服务。

更多的介绍可以参考官方文档：Seata快速入门
本篇主要是介绍Spring Cloud Alibaba + JPA 整合 Seata 的过程

安装Seata

• 下载Seata，打开 https://github.com/seata/seata/releases，现在最新的是1.3.0，所以选择seata-server-1.3.0.tar.gz 进行下载，放到/opt
• 解压Seata到/usr/local目录下

cd /opt
tar -zxvf seata-server-1.3.0.tar.gz -C /usr/local
cd /usr/local/seata/

• 这边采用file单机模式（db模式相对麻烦一点，以后再另外介绍，从简单的先开始），直接运行命令启动即可

./bin/seata-server.sh

看到下面这个提示，说明启动成功，默认端口号8091

接下来介绍Spring Cloud Alibaba 接入Seata

业务场景

假设当前存在2个微服务：订单服务、支付服务。

• 用户下单时，订单服务需要调用支付服务进行扣款
• 当余额充足时下单成功，并全局提交事务
• 当余额不足时下单失败，并全局回滚事务

版本说明

框架	版本号
Spring Boot	2.1.13.RELEASE
Spring Cloud	Greenwich.SR6
Spring Cloud Alibaba	2.1.3.RELEASE
MySQL	8.0.11

创建父工程

创建父工程 hello-alibaba-seata，并引入依赖：

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.springframework.cloudgroupId>
      <artifactId>spring-cloud-dependenciesartifactId>
      <version>${spring-cloud-version}version>
      <type>pomtype>
      <scope>importscope>
    dependency>
    <dependency>
      <groupId>com.alibaba.cloudgroupId>
      <artifactId>spring-cloud-alibaba-dependenciesartifactId>
      <version>${spring-cloud-alibaba-version}version>
      <type>pomtype>
      <scope>importscope>
    dependency>
  dependencies>
dependencyManagement>

<dependencies>
  
  <dependency>
    <groupId>org.springframework.bootgroupId>
    <artifactId>spring-boot-starter-webartifactId>
  dependency>
  <dependency>
    <groupId>org.springframework.bootgroupId>
    <artifactId>spring-boot-starter-actuatorartifactId>
  dependency>
  <dependency>
    <groupId>org.springframework.bootgroupId>
    <artifactId>spring-boot-starter-data-jpaartifactId>
  dependency>

  
  <dependency>
    <groupId>com.alibaba.cloudgroupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
  dependency>

  
  <dependency>
    <groupId>com.alibaba.cloudgroupId>
    <artifactId>spring-cloud-starter-alibaba-seataartifactId>
  dependency>

  
  <dependency>
    <groupId>mysqlgroupId>
    <artifactId>mysql-connector-javaartifactId>
    <version>${mysql.version}version>
  dependency>

    <dependency>
        <groupId>org.projectlombokgroupId>
        <artifactId>lombokartifactId>
        <optional>trueoptional>
    dependency>
dependencies>

创建公共服务 common-server

该工程主要封装公共的VO，由于测试场景比较简单，目前只有一个类

@Data
@Builder
public class ReduceAmountDto {
     
    private Long userId;
    private Integer amount;
}

创建支付服务 pay-order

在订单-支付的关系中，支付服务相当于provider，订单服务相当于consumer。因此，这边我们先创建支付服务。

• 引入 common-server 依赖

    <dependencies>
        <dependency>
            <groupId>com.traingroupId>
            <artifactId>common-serverartifactId>
            <version>${project.parent.version}version>
        dependency>
    dependencies>

• 创建账户 Entity

@Data
@Entity
@Table(name = "t_account")
public class AccountInfo {
     
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    /**
     * 用户id
     */
    @Column(name = "user_id")
    private Long userId;
    /**
     * 余额
     */
    @Column(name = "amount")
    private Integer amount;
}

• 创建Dao

public interface AccountDao extends CrudRepository<AccountInfo, Long> {
     
    /**
     *  根据userId获取账户信息
     */
    @Query(value = "SELECT a FROM AccountInfo a where a.userId = :userId")
    AccountInfo getByUserId(@Param("userId") Long userId);
    /**
     *  扣减账户余额
     */
    @Modifying
    @Query("UPDATE AccountInfo SET amount = amount - :amount WHERE userId = :userId")
    Integer reduceAmount(@Param("userId") Long userId, @Param("amount") Integer amount);
}

• 创建 Service

@Service
public class PayServiceImpl implements PayService {
     

    @Autowired
    private AccountDao accountDao;

    @Override
    @Transactional(rollbackFor = Exception.class)
    public void reduceAmount(Long userId, Integer reduceAmount) throws Exception {
     
        checkAmount(userId, reduceAmount);

        accountDao.reduceAmount(userId, reduceAmount);
    }

    private void checkAmount(Long userId, Integer reduceAmount) throws Exception {
     
        AccountInfo accountInfo = accountDao.getByUserId(userId);
        if (accountInfo == null){
     
            throw new Exception("找不到账户信息");
        }
        if (accountInfo.getAmount() < reduceAmount){
     
            throw new Exception("余额不足");
        }
    }
}

• 创建 controller

@RestController
@RequestMapping("/pay")
public class PayController {
     

    @Autowired
    private PayService payService;

    @PostMapping("/reduceAmount")
    public String reduceAmount(@RequestBody ReduceAmountDto input) throws Exception {
     
        payService.reduceAmount(input.getUserId(), input.getAmount());
        return "扣款成功";
    }
}

• application.yml

server:
  port: 8012

spring:
  application:
    name: pay-server
  jpa:
    database: mysql
  datasource:
    url: jdbc:mysql://192.168.25.129:3306/pay_db?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=UTF-8&useSSL=false
    username: test
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
  cloud:
    nacos:
      discovery:
        server-addr: 192.168.25.131:8848
management:
  endpoints:
    web:
      exposure:
        include: "*"

seata:
  enabled: true
  application-id: ${
     spring.application.name}
  tx-service-group: my_test_tx_group
  service:
    vgroup-mapping:
      my_test_tx_group: default
    grouplist:
      default: 192.168.25.131:8091
  config:
    type: file
    file:
      name: file.conf
  registry:
    type: file
    file:
      name: file.conf
  enable-auto-data-source-proxy: true

注意：如果用的不是MySQL8，就要改下 driver-class-name

创建订单服务 order-server

• 引入 common-server 依赖

    <dependencies>
        <dependency>
            <groupId>com.traingroupId>
            <artifactId>common-serverartifactId>
            <version>${project.parent.version}version>
        dependency>
    dependencies>

• 创建订单 Entity

@Data
@Entity
@Table(name = "t_order")
public class Orders {
     
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    /**
     * 用户id
     */
    @Column(name = "user_id")
    private Long userId;
    /**
     * 金额
     */
    @Column(name = "amount")
    private Integer amount;
}

• 创建订单 Dao

public interface OrdersDao extends CrudRepository<Orders, Long> {
     
}

• 创建 Service

@Service
@Slf4j
public class OrderServiceImpl implements OrderService {
     

    @Autowired
    private OrdersDao orderDao;
    @Autowired
    private RestTemplate restTemplate;

    @Override
    @GlobalTransactional
    public void save(Orders order) {
     
        orderDao.save(order);

        //扣款
        String reduceUrl = "http://pay-server/pay/reduceAmount";
        ReduceAmountDto input = ReduceAmountDto.builder().userId(order.getUserId()).amount(order.getAmount()).build();
        String result = restTemplate.postForObject(reduceUrl, input, String.class);

        log.info("调用pay-server结果：" + result);
    }
}

@GlobalTransactional 表示开启Seata全局事务

• 创建 controller

@RestController
@RequestMapping("/order")
public class OrderController {
     

    @Autowired
    private OrderService orderService;

    @RequestMapping("/save")
    public String save(@RequestBody Orders order){
     
        orderService.save(order);
        return "操作结束";
    }
}

测试

1. 启动Nacos
2. 启动Seata
3. 启动pay-server
4. 启动order-server
5. 调用创建订单接口 http://localhost:8011/order/save ，构造相应的测试数据进行测试就行