spring:
  datasource:
    master:
      url: jdbc:mysql://localhost:3306/master_db
      username: root
      password: root
      driver-class-name: com.mysql.cj.jdbc.Driver
    slave:
      url: jdbc:mysql://localhost:3306/slave_db
      username: root
      password: root
      driver-class-name: com.mysql.cj.jdbc.Driver

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        // 從線程上下文中獲取當(dāng)前數(shù)據(jù)源標(biāo)識(shí)
        return DataSourceContextHolder.getDataSource();
    }
}

public class DataSourceContextHolder {
    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

    public static void setDataSource(String dataSource) {
        contextHolder.set(dataSource);
    }

    public static String getDataSource() {
        return contextHolder.get();
    }

    public static void clearDataSource() {
        contextHolder.remove();
    }
}

@Configuration
public class DataSourceConfig {

    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource masterDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "slaveDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource slaveDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @Primary
    public DataSource dynamicDataSource(
        @Qualifier("masterDataSource") DataSource masterDataSource,
        @Qualifier("slaveDataSource") DataSource slaveDataSource) {
        
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put("master", masterDataSource);
        targetDataSources.put("slave", slaveDataSource);

        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        dynamicDataSource.setTargetDataSources(targetDataSources);
        dynamicDataSource.setDefaultTargetDataSource(masterDataSource); // 默認(rèn)使用主數(shù)據(jù)源
        return dynamicDataSource;
    }
}

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

    @Autowired
    private DataSource dynamicDataSource;

    @Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dynamicDataSource);
        return factoryBean.getObject();
    }
}

// 切換到從數(shù)據(jù)源（讀操作）
DataSourceContextHolder.setDataSource("slave");
try {
    // 執(zhí)行查詢操作
    List<User> users = userMapper.selectAll();
} finally {
    // 清除線程上下文
    DataSourceContextHolder.clearDataSource();
}

// 切換到主數(shù)據(jù)源（寫(xiě)操作）
DataSourceContextHolder.setDataSource("master");
try {
    userMapper.insert(user);
} finally {
    DataSourceContextHolder.clearDataSource();
}

@Configuration
@EnableTransactionManagement
public class TransactionConfig {

    @Bean(name = "masterTransactionManager")
    public PlatformTransactionManager masterTransactionManager(
        @Qualifier("masterDataSource") DataSource masterDataSource) {
        return new DataSourceTransactionManager(masterDataSource);
    }

    @Bean(name = "slaveTransactionManager")
    public PlatformTransactionManager slaveTransactionManager(
        @Qualifier("slaveDataSource") DataSource slaveDataSource) {
        return new DataSourceTransactionManager(slaveDataSource);
    }
}

// 在 Service 層指定事務(wù)管理器
@Service
public class UserService {

    @Transactional("masterTransactionManager")
    public void insertUser(User user) {
        userMapper.insert(user);
    }

    @Transactional("slaveTransactionManager")
    public List<User> selectAllUsers() {
        return userMapper.selectAll();
    }
}