Spring使用@Async注解，造成循环依赖Bean问题

在做项目的时候，因为一个功能过于复杂，把它变成异步执行，加上@Asyac注解，然后启动报错。

• 简单模拟场景：

@Service
public class ServiceA implements IServiceA{
    @Autowired
    private IServiceB iServiceB;

    @Async
    @Override
    public void say(String str) {
        iServiceB.say("I'am serviceB");
    }
}

@Service
public class ServiceB implements IServiceB{
    @Autowired
    private IServiceA iServiceA;

    @Async
    @Override
    public void say(String name) {
        iServiceA.say("I'am serviceA");
    }
}

• 启动报以下错误：

org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'serviceA': Bean with name 'serviceA' has been injected into other beans [serviceB] 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:585) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at com.example.curdemo.CurdemoApplication.main(CurdemoApplication.java:12) [classes/:na]

• 解决办法： 加上@Lazy注解延迟加载

   @Autowired
   @Lazy
   private IServiceA iServiceA;

   @Autowired
   @Lazy
   private IServiceB iServiceB;

• 分析原因
  程序在正常加载完循环依赖之后，遇到了@Async注解，Spring需要对其代理一次，导致Bean又需要初始化一次，但Spring中该Bean已经被注入，且注入的是没被代理过的版本，于是报错。

• 详情原因分析，参考以下文章
  https://blog.csdn.net/lianhuazy167/article/details/66967673