spring-cloud-openfeign
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Confusing behaviour: empty URL not allowed with default Client, but possible with ApacheHttpClient
My issue is related to https://github.com/spring-cloud/spring-cloud-openfeign/issues/517.
I found after some debugging that contrary to the situation described in that ticket, if ApacheHttpClient
is on the classpath (in my case through a dependency on io.github.openfeign:feign-httpclient
), it is very well possible to specify an empty String for the url
in a @FeignClient
(in my case, I did it like this: @FeignClient(name = "myfeignclient", url = "${my.url:}")
, i.e. with an empty String as default value and the property being absent).
This allows the context to come up at least and will only result in an UnknownHostException
when a request is actually attempted to be sent through that FeignClient.
For us, this is quite convenient though in a development environment where the destination is not known or when working on someone else's project so not all the required configuration needs to be known.
The crucial difference seems to be in the method loadBalance
in FeignClientFactoryBean
. Without the ApacheHttpClient
being available as a bean, getOptional
returns null
, leading to the IllegalStateException
.
A bean of type ApacheHttpClient
seemingly becomes registered through FeignAutoConfiguration.HttpClientFeignConfiguration
.
I'm thinking that if the Client.Default
implementation was exposed as a bean, both situations would behave the same.
Would this be a reasonable change? I read @OlgaMaciaszek's point on the other ticket that it is intended to fail(?) by design, but why should it work then with ApacheHttpClient
? (please don't take away that possibility though, like I said above, we like it :wink:)
@jo-ka, you're right - the behaviour is not consistent and adding a Client
bean could be done, however, I don't think it would bring a lot of functionality improvement, so will leave it is at is for now, unless we get more requests about it from the community.