踩坑日记---PathVariable annotation was empty on param 0

先上错误:

Caused by: java.lang.IllegalStateException: PathVariable annotation was empty on param 0.
	at feign.Util.checkState(Util.java:130) ~[feign-core-10.4.0.jar:na]
	at org.springframework.cloud.openfeign.annotation.PathVariableParameterProcessor.processArgument(PathVariableParameterProcessor.java:52) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.cloud.openfeign.support.SpringMvcContract.processAnnotationsOnParameter(SpringMvcContract.java:292) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at feign.Contract$BaseContract.parseAndValidateMetadata(Contract.java:110) ~[feign-core-10.4.0.jar:na]
	at org.springframework.cloud.openfeign.support.SpringMvcContract.parseAndValidateMetadata(SpringMvcContract.java:188) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:66) ~[feign-core-10.4.0.jar:na]
	at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:154) ~[feign-core-10.4.0.jar:na]
	at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:52) ~[feign-core-10.4.0.jar:na]
	at feign.Feign$Builder.target(Feign.java:251) ~[feign-core-10.4.0.jar:na]
	at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:38) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:243) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:272) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:252) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	... 35 common frames omitted

定位到错误代码处:

@GetMapping("/payment/{id}")
    public CommonResult<Payment> getById(@PathVariable Long id);

咋一看没错呀，我猜碰到这问题的都是玩feign或openfeign的小伙伴吧，这个参数需要指定参数名，不然绑定不上，修改后的代码:

@GetMapping("/payment/{id}")
    public CommonResult<Payment> getById(@PathVariable("id") Long id);

至于原因，我目前也不知道，需要查看它的源码。