Dubbo服务启动失败：＜dubbo:service interface=““ /＞ interface not allow null!

最近升级框架版本：

spring boot：2.2.5 --> 2.3.2

spring cloud：Hoxton.SR3 --> Hoxton.SR8

spring cloud alibaba：2.2.1 --> 2.2.3

dubbo：2.7.6 --> 2.7.8

升级后某服务启动失败，异常日志：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'xxxController' defined in file [xxxController.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'ServiceBean:IXxxDubboService': Cannot resolve reference to bean 'bDubboServiceProvider' while setting bean property 'ref'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'bDubboServiceProvider': Unsatisfied dependency expressed through field 'xxxService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'aServiceImpl' defined in file [aServiceImpl.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'ServiceBean:IzzzDubboService': Cannot resolve reference to bean 'cDubboServiceProvider' while setting bean property 'ref'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'cDubboServiceProvider': Injection of @DubboReference dependencies is failed; nested exception is java.lang.IllegalStateException:  interface not allow null!
......
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'bDubboServiceProvider': Injection of @DubboReference dependencies is failed; nested exception is java.lang.IllegalStateException:  interface not allow null!
......

问题原因：经排查发现是某位开发同事写的a服务和b服务（dubbo）互相引用导致，但是在原版本中没有此异常发生。

解决方案：与spring的循环依赖类似，最简单的方案是在引用的服务实例上加@Lazy注解，最合理的方案是做代码拆分，写服务代码时还是要多加注意。