[REQ] Extend JavaSpring apiClient.mustache with option to override contextId for FeignClient

[paveliam]

Is your feature request related to a problem? Please describe.

When you try to generate JavaSpring FeignClients for the same service but from different API specs (e.g. 1st spec for Internal API, 2nd one for Admin API), you will get an error on load ApplicationContext as there is a conflict in aliases which are generated from the same service name.

Caused by: java.lang.IllegalStateException: Cannot define alias 'service-nameFeignClient' for name 'com.example.api.MyServiceInternalApiClient': It is already registered for name 'com.example.api.MyServiceAdminApiClient'.
	at org.springframework.core.SimpleAliasRegistry.registerAlias(SimpleAliasRegistry.java:73)
	at org.springframework.beans.factory.support.BeanDefinitionReaderUtils.registerBeanDefinition(BeanDefinitionReaderUtils.java:170)

Describe the solution you'd like

I propose to extend

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-cloud/apiClient.mustache#L6C90-L6C111

with an option to define contextId as well. By default it can be equal to name.
By specifying contextId for FeignClient there won't be a conflict in aliases.

Here is how it may look like:

package {{package}};

import org.springframework.cloud.openfeign.FeignClient;
import {{configPackage}}.ClientConfiguration;

@FeignClient(
    name="${{openbrace}}{{classVarName}}.name:{{classVarName}}{{closebrace}}",
    {{#useFeignClientContextId}}contextId="${{openbrace}}{{classVarName}}.contextId:${{openbrace}}{{classVarName}}.name{{closebrace}}{{closebrace}}",{{/useFeignClientContextId}}
    {{#useFeignClientUrl}}url="${{openbrace}}{{classVarName}}.url:{{basePath}}{{closebrace}}",{{/useFeignClientUrl}}
    configuration = ClientConfiguration.class
)
public interface {{classname}}Client extends {{classname}} {
}

Describe alternatives you've considered

As a workaround I have to create manually feign clients if there are such conflicts which is annoying.

[paveliam]

Here is the PR with the suggested changes: #20943

[YevgenyDrozdov]

Hello @wing328, I'm interested in this feature. Could you help with releasing a new version of the generator?
Thank you in advance.