Spring-boot EntityListener，application context中部分bean的依赖形成一个循环

Question

我在以下设计中面临依赖循环（摘自 here）。

我有 2 个实体 Post 和 PostLog。创建 Post 后，我也想将其保存在 PostLog 中。因此创建了侦听器并将其应用于“Post”实体。实体 Post 和 PostLog 也都使用 spring-boot “AuditingEntityListener”，但为了简单起见，我不在此处添加该代码。

我的实体和监听器结构 -

@Data
@EqualsAndHashCode(callSuper = false)
@Entity
@Table(name = "post")
@EntityListeners({AuditingEntityListener.class, PostLogListener.class})
public class Post extends Auditable<String> {
...
}

@Data
@EqualsAndHashCode(callSuper = false)
@Entity
@Table(name = "post_log")
@EntityListeners(AuditingEntityListener.class)
public class PostLog extends Auditable<String> {
...
}

@Component
@RequiredArgsConstructor
public class PostLogListener {
  
  private final PostLogRepository repo;

  @PostPersist
  @Transactional(propagation = Propagation.REQUIRES_NEW)
  public void logEvent(final Post post) {
    PostLog log = createLog(post); // implementation is omitted here for keeping short
    repo.save(log);
  }
}

@Repository
public interface PostLogRepository extends CrudRepository<PostLog, Long> {}

我收到错误 -

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

┌─────┐
|  entityManagerFactory defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]
↑     ↓
|  com.example.listener.PostLogListener
↑     ↓
|  postLogRepository defined in com.example.repository.PostLogRepository defined in @EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration
↑     ↓
|  (inner bean)#53c2dd3a
└─────┘

我做了一些研究，但找不到合适的解决方案。

Answer 1

使用惰性初始化解决循环依赖。为此，您需要自己创建构造函数以注入 spring bean 并使用 @Lazy (org.springframework.context.annotation.Lazy)

@Component
public class PostLogListener {
  
  private final PostLogRepository repo;

  public PostLogListener(@Lazy PostLogRepository repo) {
    this.repo = repo;
  }

  @PostPersist
  @Transactional(propagation = Propagation.REQUIRES_NEW)
  public void logEvent(final Post post) {
    PostLog log = createLog(post); // implementation is omitted here for keeping short
    repo.save(log);
  }
}

Note - This is required if any of the injected beans depends on the EntityManager. Spring Data repositories depend on EntityManager, so any bean having a repository or a direct entityManager will make a circle.

Spring-boot EntityListener，application context中部分bean的依赖形成一个循环

Spring-boot EntityListener, The dependencies of some of the beans in the application context form a cycle

java

spring-boot

jpa

dependency-injection

entitylisteners