spring:
  datasource:
    # 默認(rèn)數(shù)據(jù)源配置
    primary:
      url: jdbc:mysql://localhost:3306/primary_db
      username: root
      password: password
      driver-class-name: com.mysql.cj.jdbc.Driver
      hikari:
        maximum-pool-size: 10
    
    # 第二數(shù)據(jù)源配置
    secondary:
      url: jdbc:mysql://localhost:3306/secondary_db
      username: root
      password: password
      driver-class-name: com.mysql.cj.jdbc.Driver
      hikari:
        maximum-pool-size: 10

@Configuration
@EnableTransactionManagement
public class DataSourceConfig {

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

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

@Configuration
public class DynamicDataSourceConfig {

    @Autowired
    @Qualifier("primaryDataSource")
    private DataSource primaryDataSource;

    @Autowired
    @Qualifier("secondaryDataSource")
    private DataSource secondaryDataSource;

    @Bean
    public DataSource dataSource() {
        // 創(chuàng)建一個(gè)路由數(shù)據(jù)源
        DynamicDataSource dataSource = new DynamicDataSource();
        dataSource.setDefaultTargetDataSource(primaryDataSource); // 默認(rèn)數(shù)據(jù)源
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put("primary", primaryDataSource);
        targetDataSources.put("secondary", secondaryDataSource);
        dataSource.setTargetDataSources(targetDataSources);
        return dataSource;
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource {

    // 從 ThreadLocal 獲取當(dāng)前的數(shù)據(jù)庫(kù)標(biāo)識(shí)
    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.getDataSourceType();
    }
}

public class DataSourceContextHolder {

    // 使用 ThreadLocal 存儲(chǔ)當(dāng)前線程的數(shù)據(jù)源標(biāo)識(shí)
    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

    public static void setDataSourceType(String dataSourceType) {
        contextHolder.set(dataSourceType);
    }

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

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

@Aspect
@Component
public class DataSourceAspect {

    // 通過(guò)注解來(lái)指定使用哪個(gè)數(shù)據(jù)源
    @Before("@annotation(dataSource)")
    public void switchDataSource(DataSourceType dataSource) {
        // 切換數(shù)據(jù)源
        DataSourceContextHolder.setDataSourceType(dataSource.value());
    }

    @After("@annotation(dataSource)")
    public void clearDataSource(DataSourceType dataSource) {
        // 清理數(shù)據(jù)源標(biāo)識(shí)，避免影響其他線程
        DataSourceContextHolder.clearDataSourceType();
    }
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DataSourceType {

    String value() default "primary";  // 數(shù)據(jù)源標(biāo)識(shí)，默認(rèn)使用primary數(shù)據(jù)源
}

@Service
public class UserService {

    @DataSourceType("primary")
    public List<User> getPrimaryUsers() {
        // 查詢主數(shù)據(jù)庫(kù)
        return userRepository.findAll();
    }

    @DataSourceType("secondary")
    public List<User> getSecondaryUsers() {
        // 查詢次數(shù)據(jù)庫(kù)
        return secondaryUserRepository.findAll();
    }
}