Spring Boot循环依赖原理、解决方案与最佳实践(全解析)

@Service  
public class ServiceA {  
    @Autowired  
    private ServiceB serviceB;  
}  
@Service  
public class ServiceB {  
    @Autowired  
    private ServiceA serviceA;  
}  

1. 创建ServiceA → 将原始对象工厂放入三级缓存  
2. 填充ServiceA属性 → 发现需要ServiceB  
3. 创建ServiceB → 将原始对象工厂放入三级缓存  
4. 填充ServiceB属性 → 从三级缓存获取ServiceA的工厂 → 生成代理对象  
5. ServiceB初始化完成 → 移入一级缓存  
6. ServiceA继续填充ServiceB → 从一级缓存获取ServiceB → 完成初始化  

// 错误示例：启动直接失败  
@Service  
public class ServiceA {  
    private final ServiceB serviceB;  
    public ServiceA(ServiceB serviceB) {  
        this.serviceB = serviceB;  
    }  
}  
@Service  
public class ServiceB {  
    private final ServiceA serviceA;  
    public ServiceB(ServiceA serviceA) {  
        this.serviceA = serviceA;  
    }  
}  

# application.properties  
spring.main.allow-circular-references=true  

@Service  
public class ServiceA {  
    private ServiceB serviceB;  
    @Autowired  
    public void setServiceB(ServiceB serviceB) {  
        this.serviceB = serviceB;  
    }  
}  
@Service  
public class ServiceB {  
    private ServiceA serviceA;  
    @Autowired  
    public void setServiceA(ServiceA serviceA) {  
        this.serviceA = serviceA;  
    }  
}  

@Service  
public class ServiceA {  
    @Lazy  
    @Autowired  
    private ServiceB serviceB;  
}  

public interface IServiceA {  
    void doSomething();  
}  
public interface IServiceB {  
    void doAnother();  
}  
@Service  
public class ServiceAImpl implements IServiceA {  
    @Autowired  
    private IServiceB serviceB;  
}  
@Service  
public class ServiceBImpl implements IServiceB {  
    @Autowired  
    private IServiceA serviceA;  
}  

// 定义数据访问接口  
public interface UserRepository {  
    User findById(Long id);  
}  
// 高层服务依赖接口  
@Service  
public class UserService {  
    private final UserRepository repository;  
    public UserService(UserRepository repository) {  
        this.repository = repository;  
    }  
}  
// 低层实现  
@Repository  
public class JpaUserRepository implements UserRepository {  
    // 实现细节  
}  

// ServiceA发布事件  
@Service  
public class ServiceA {  
    @Autowired  
    private ApplicationEventPublisher publisher;  
    public void triggerEvent() {  
        publisher.publishEvent(new CustomEvent(this));  
    }  
}  
// ServiceB监听事件  
@Service  
public class ServiceB {  
    @EventListener  
    public void handleEvent(CustomEvent event) {  
        // 处理逻辑  
    }  
}  

<plugin>  
    <groupId>org.springframework.boot</groupId>  
    <artifactId>spring-boot-maven-plugin</artifactId>  
    <configuration>  
        <excludes>  
            <exclude>  
                <groupId>org.projectlombok</groupId>  
                <artifactId>lombok</artifactId>  
            </exclude>  
        </excludes>  
    </configuration>  
</plugin>  

mvn spring-boot:run -Dspring-boot.run.profiles=dev