记一次循环依赖问题

什么是循环依赖？

BeanA依赖BeanB，BeanB依赖BeanA。
以此类推
BeanA依赖BeanB，BeanB依赖BeanC，BeanC依赖BeanA。

项目中没有使用构造器注入的方式。理论上不会出现循环依赖。

public class appUserService {
   @Autowired
   private BalanceCashOutJobService balanceCashOutJobService;

  @Autowired
  private DistributionPersonnelService distributionPersonnelService;
......
代码略
}

出现报错

Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'appUserService': Bean with name 'appUserService' has been injected into other beans [balanceCashOutJobService,distributionPersonnelService] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:622)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1248)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1168)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593)
    ... 45 common frames omitted

解决

经过排查，在configuration配置类里使用了 BeanPostProcessor

@Bean
    public LifecycleBeanPostProcessor lifecycleBeanPostProcessor() {
        return new LifecycleBeanPostProcessor();
    }

参考
https://www.jianshu.com/p/f17882274dda?from=timeline&isappinstalled=0

BeanPostProcessor接口是用来对bean进行后置处理的，这个时候bean已经完成实例化和依赖注入了，属于bean初始化生命周期的一部分。
当有循环依赖出现时，Bean中注入的bean不是最终的版本，而是spring 三级缓存中的第二级缓存引用。然而这个引用在完成bean注入后将发生改变。导致注入的bean跟最终生成的bean不是同一个。