【错误解决】java.lang.IllegalStateException: PathVariable annotation was empty on param 0.

报错：java.lang.IllegalStateException: PathVariable annotation was empty on param 0.

问题描述：

微服务启动失败，层层嵌套报错，最后错误为：java.lang.IllegalStateException: PathVariable annotation was empty on param 0.

org.springframework.beans.factory.BeanCreationNotAllowedException: Error creating bean with name 'rabbitConnectionFactory': Singleton bean creation not allowed while singletons of this factory are in destruction (Do not request a bean from a BeanFactory in a destroy method implementation!)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:220)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207)
	at org.springframework.context.event.AbstractApplicationEventMulticaster.retrieveApplicationListeners(AbstractApplicationEventMulticaster.java:247)
	at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:204)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:134)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:410)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361)
	at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1013)
	at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:979)
	at org.springframework.cloud.context.named.NamedContextFactory.destroy(NamedContextFactory.java:93)
	at org.springframework.beans.factory.support.DisposableBeanAdapter.destroy(DisposableBeanAdapter.java:258)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroyBean(DefaultSingletonBeanRegistry.java:587)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingleton(DefaultSingletonBeanRegistry.java:559)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingleton(DefaultListableBeanFactory.java:1092)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingletons(DefaultSingletonBeanRegistry.java:520)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingletons(DefaultListableBeanFactory.java:1085)
	at org.springframework.context.support.AbstractApplicationContext.destroyBeans(AbstractApplicationContext.java:1061)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:564)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java