Overriding Feign Defaults
A central concept in Spring Cloud’s Feign support is that of the named client. Each feign client is part of an ensemble of components that work together to contact a remote server on demand, and the ensemble has a name that you give it as an application developer using the @FeignClient
annotation. Spring Cloud creates a new ensemble as an
ApplicationContext
on demand for each named client using FeignClientsConfiguration
. This contains (amongst other things) an feign.Decoder
, a feign.Encoder
, and a feign.Contract
.
It is possible to override the name of that ensemble by using the contextId
attribute of the @FeignClient
annotation.
Spring Cloud lets you take full control of the feign client by declaring additional configuration (on top of the FeignClientsConfiguration
) using @FeignClient
. Example:
@FeignClient(name = "stores", configuration = FooConfiguration.class)
public interface StoreClient {
//..
}
In this case the client is composed from the components already in FeignClientsConfiguration
together with any in FooConfiguration
(where the latter will override the former).
FooConfiguration does not need to be annotated with @Configuration . However, if it is, then take care to exclude it from any @ComponentScan that would otherwise include this configuration as it will become the default source for feign.Decoder , feign.Encoder , feign.Contract , etc., when specified. This can be avoided by putting it in a separate, non-overlapping package from any @ComponentScan or @SpringBootApplication , or it can be explicitly excluded in @ComponentScan .
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The serviceId attribute is now deprecated in favor of the name attribute.
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Using contextId attribute of the @FeignClient annotation in addition to changing the name of
the ApplicationContext ensemble, it will override the alias of the client name
and it will be used as part of the name of the configuration bean created for that client.
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Previously, using the url attribute, did not require the name attribute. Using name is now required.
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Placeholders are supported in the name
and url
attributes.
@FeignClient(name = "${feign.name}", url = "${feign.url}")
public interface StoreClient {
//..
}
Spring Cloud Netflix provides the following beans by default for feign (BeanType
beanName: ClassName
):
-
Decoder
feignDecoder:ResponseEntityDecoder
(which wraps aSpringDecoder
) -
Encoder
feignEncoder:SpringEncoder
-
Logger
feignLogger:Slf4jLogger
-
Contract
feignContract:SpringMvcContract
-
Feign.Builder
feignBuilder:HystrixFeign.Builder
-
Client
feignClient: if Ribbon is in the classpath and is enabled it is aLoadBalancerFeignClient
, otherwise if Spring Cloud LoadBalancer is in the classpath,FeignBlockingLoadBalancerClient
is used. If none of them is in the classpath, the default feign client is used.
spring-cloud-starter-openfeign contains both spring-cloud-starter-netflix-ribbon and spring-cloud-starter-loadbalancer .
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The OkHttpClient and ApacheHttpClient feign clients can be used by setting feign.okhttp.enabled
or feign.httpclient.enabled
to true
, respectively, and having them on the classpath.
You can customize the HTTP client used by providing a bean of either org.apache.http.impl.client.CloseableHttpClient
when using Apache or okhttp3.OkHttpClient
when using OK HTTP.
Spring Cloud Netflix does not provide the following beans by default for feign, but still looks up beans of these types from the application context to create the feign client:
-
Logger.Level
-
Retryer
-
ErrorDecoder
-
Request.Options
-
Collection<RequestInterceptor>
-
SetterFactory
-
QueryMapEncoder
Creating a bean of one of those type and placing it in a @FeignClient
configuration (such as FooConfiguration
above) allows you to override each one of the beans described. Example:
@Configuration
public class FooConfiguration {
@Bean
public Contract feignContract() {
return new feign.Contract.Default();
}
@Bean
public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
return new BasicAuthRequestInterceptor("user", "password");
}
}
This replaces the SpringMvcContract
with feign.Contract.Default
and adds a RequestInterceptor
to the collection of RequestInterceptor
.
@FeignClient
also can be configured using configuration properties.
application.yml
feign:
client:
config:
feignName:
connectTimeout: 5000
readTimeout: 5000
loggerLevel: full
errorDecoder: com.example.SimpleErrorDecoder
retryer: com.example.SimpleRetryer
requestInterceptors:
- com.example.FooRequestInterceptor
- com.example.BarRequestInterceptor
decode404: false
encoder: com.example.SimpleEncoder
decoder: com.example.SimpleDecoder
contract: com.example.SimpleContract
Default configurations can be specified in the @EnableFeignClients
attribute defaultConfiguration
in a similar manner as described above. The difference is that this configuration will apply to all feign clients.
If you prefer using configuration properties to configured all @FeignClient
, you can create configuration properties with default
feign name.
application.yml
feign:
client:
config:
default:
connectTimeout: 5000
readTimeout: 5000
loggerLevel: basic
If we create both @Configuration
bean and configuration properties, configuration properties will win.
It will override @Configuration
values. But if you want to change the priority to @Configuration
,
you can change feign.client.default-to-properties
to false
.
If you need to use ThreadLocal bound variables in your RequestInterceptor`s you will need to either set the
thread isolation strategy for Hystrix to `SEMAPHORE or disable Hystrix in Feign.
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application.yml
# To disable Hystrix in Feign
feign:
hystrix:
enabled: false
# To set thread isolation to SEMAPHORE
hystrix:
command:
default:
execution:
isolation:
strategy: SEMAPHORE
If we want to create multiple feign clients with the same name or url
so that they would point to the same server but each with a different custom configuration then
we have to use contextId
attribute of the @FeignClient
in order to avoid name
collision of these configuration beans.
@FeignClient(contextId = "fooClient", name = "stores", configuration = FooConfiguration.class)
public interface FooClient {
//..
}
@FeignClient(contextId = "barClient", name = "stores", configuration = BarConfiguration.class)
public interface BarClient {
//..
}