MyBatis中如何实现分布式事务管理

在MyBatis中实现分布式事务管理，通常需要借助外部的事务管理器，如Atomikos、Bitronix或Narayana等。这些事务管理器能够支持XA协议，从而实现跨多个数据库或资源管理器的事务控制。以下是使用Atomikos作为分布式事务管理器的示例步骤：

1. 添加依赖

首先，在项目的pom.xml文件中添加Atomikos和MyBatis的相关依赖：

<dependencies>
    <!-- MyBatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.0.6</version>
    </dependency>
    <!-- Atomikos -->
    <dependency>
        <groupId>com.atomikos</groupId>
        <artifactId>transactions-jdbc</artifactId>
        <version>5.0.8</version>
    </dependency>
    <dependency>
        <groupId>com.atomikos</groupId>
        <artifactId>transactions-jta</artifactId>
        <version>5.0.8</version>
    </dependency>
    <!-- 数据库驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.23</version>
    </dependency>
</dependencies>

2. 配置数据源

配置两个或多个数据源，并使用Atomikos的AtomikosDataSourceBean来包装它们：

import com.atomikos.jdbc.AtomikosDataSourceBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;

import javax.sql.DataSource;
import java.util.Properties;

@Configuration
public class DataSourceConfig {

    @Bean(name = "dataSource1")
    public DataSource dataSource1() {
        AtomikosDataSourceBean dataSource = new AtomikosDataSourceBean();
        dataSource.setUniqueResourceName("dataSource1");
        dataSource.setXaDataSourceClassName("com.mysql.cj.jdbc.MysqlXADataSource");
        Properties xaProperties = new Properties();
        xaProperties.setProperty("url", "jdbc:mysql://localhost:3306/db1");
        xaProperties.setProperty("user", "user1");
        xaProperties.setProperty("password", "password1");
        dataSource.setXaProperties(xaProperties);
        dataSource.setPoolSize(5);
        return dataSource;
    }

    @Bean(name = "dataSource2")
    public DataSource dataSource2() {
        AtomikosDataSourceBean dataSource = new AtomikosDataSourceBean();
        dataSource.setUniqueResourceName("dataSource2");
        dataSource.setXaDataSourceClassName("com.mysql.cj.jdbc.MysqlXADataSource");
        Properties xaProperties = new Properties();
        xaProperties.setProperty("url", "jdbc:mysql://localhost:3306/db2");
        xaProperties.setProperty("user", "user2");
        xaProperties.setProperty("password", "password2");
        dataSource.setXaProperties(xaProperties);
        dataSource.setPoolSize(5);
        return dataSource;
    }

    @Bean(name = "transactionManager")
    public PlatformTransactionManager transactionManager() {
        return new DataSourceTransactionManager(dataSource1());
    }
}

3. 配置MyBatis

配置MyBatis使用Atomikos事务管理器：

import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.example.mapper", sqlSessionFactoryRef = "sqlSessionFactory")
public class MyBatisConfig {

    @Bean(name = "sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(dataSource);
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources("classpath*:mapper/*.xml"));
        return sessionFactory.getObject();
    }
}

4. 使用分布式事务

在服务层方法上使用@Transactional注解，并指定事务管理器：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper1;

    @Autowired
    private UserMapper userMapper2;

    @Transactional(transactionManager = "transactionManager")
    public void performDistributedTransaction() {
        // 操作第一个数据源
        userMapper1.insertUser(new User("user1", "password1"));

        // 操作第二个数据源
        userMapper2.insertUser(new User("user2", "password2"));
    }
}

5. 配置JTA事务管理器

确保Spring Boot应用程序配置了JTA事务管理器：

spring:
  jta:
    atomikos:
      datasource:
        unique-resource-name: dataSource1
        xa-data-source-class-name: com.mysql.cj.jdbc.MysqlXADataSource
        xa-properties:
          url: jdbc:mysql://localhost:3306/db1
          user: user1
          password: password1
        pool-size: 5
      datasource:
        unique-resource-name: dataSource2
        xa-data-source-class-name: com.mysql.cj.jdbc.MysqlXADataSource
        xa-properties:
          url: jdbc:mysql://localhost:3306/db2
          user: user2
          password: password2
        pool-size: 5

通过以上步骤，你可以在MyBatis中实现分布式事务管理。请注意，分布式事务管理会增加系统的复杂性和开销，因此在实际应用中应谨慎使用。