<dependencies>
    <!-- Spring Boot Starter -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- Mybatis-plus -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.3.1</version>
    </dependency>
    <!-- 數(shù)據(jù)庫(kù)驅(qū)動(dòng) -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <!-- 其他工具 -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

spring:
  datasource:
    master:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/master_db?useSSL=false&serverTimezone=UTC
      username: root
      password: 123456
    slave1:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/slave1_db?useSSL=false&serverTimezone=UTC
      username: root
      password: 123456
    slave2:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/slave2_db?useSSL=false&serverTimezone=UTC
      username: root
      password: 123456

public enum DataSourceType {
    MASTER("master"),
    SLAVE1("slave1"),
    SLAVE2("slave2");
    private final String name;
    DataSourceType(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
}

public class DynamicDataSourceContextHolder {
    private static final ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();
    public static void setDataSourceType(String dataSourceType) {
        CONTEXT_HOLDER.set(dataSourceType);
    }
    public static String getDataSourceType() {
        return CONTEXT_HOLDER.get();
    }
    public static void clearDataSourceType() {
        CONTEXT_HOLDER.remove();
    }
}

@Configuration
@MapperScan(basePackages = "com.example.mapper")
public class DynamicDataSourceConfig {
    @Bean
    @ConfigurationProperties("spring.datasource.master")
    public DataSource masterDataSource() {
        return DataSourceBuilder.create().build();
    }
    @Bean
    @ConfigurationProperties("spring.datasource.slave1")
    public DataSource slave1DataSource() {
        return DataSourceBuilder.create().build();
    }
    @Bean
    @ConfigurationProperties("spring.datasource.slave2")
    public DataSource slave2DataSource() {
        return DataSourceBuilder.create().build();
    }
    @Bean
    public DataSource dynamicDataSource() {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceType.MASTER.getName(), masterDataSource());
        targetDataSources.put(DataSourceType.SLAVE1.getName(), slave1DataSource());
        targetDataSources.put(DataSourceType.SLAVE2.getName(), slave2DataSource());
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        dynamicDataSource.setTargetDataSources(targetDataSources);
        dynamicDataSource.setDefaultTargetDataSource(masterDataSource());
        return dynamicDataSource;
    }
    @Bean
    public PlatformTransactionManager transactionManager(DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicDataSourceContextHolder.getDataSourceType();
    }
}

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {
    DataSourceType value() default DataSourceType.MASTER;
}

@Aspect
@Component
@Order(-1)
@Slf4j
public class DataSourceAspect {
    @Pointcut("@annotation(com.example.annotation.DataSource)" +
            "|| @within(com.example.annotation.DataSource)")
    public void dsPointCut() {
    }
    @Around("dsPointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        DataSource dataSource = getDataSource(point);
        if (dataSource != null) {
            DynamicDataSourceContextHolder.setDataSourceType(dataSource.value().getName());
        }
        try {
            return point.proceed();
        } finally {
            DynamicDataSourceContextHolder.clearDataSourceType();
        }
    }
    private DataSource getDataSource(ProceedingJoinPoint point) {
        MethodSignature signature = (MethodSignature) point.getSignature();
        DataSource dataSource = AnnotationUtils.findAnnotation(signature.getMethod(), DataSource.class);
        if (dataSource != null) {
            return dataSource;
        }
        return AnnotationUtils.findAnnotation(signature.getDeclaringType(), DataSource.class);
    }
}

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;
    @Override
    @DataSource(DataSourceType.MASTER)
    public User getMasterUser(Long id) {
        return userMapper.selectById(id);
    }
    @Override
    @DataSource(DataSourceType.SLAVE1)
    public User getSlave1User(Long id) {
        return userMapper.selectById(id);
    }
    @Override
    @DataSource(DataSourceType.SLAVE2)
    public User getSlave2User(Long id) {
        return userMapper.selectById(id);
    }
}

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;
    @GetMapping("/master/{id}")
    public User master(@PathVariable Long id) {
        return userService.getMasterUser(id);
    }
    @GetMapping("/slave1/{id}")
    public User slave1(@PathVariable Long id) {
        return userService.getSlave1User(id);
    }
    @GetMapping("/slave2/{id}")
    public User slave2(@PathVariable Long id) {
        return userService.getSlave2User(id);
    }
}