Exception while adding custom response headers from feign

[banupriya2022]

I am looking for enriching the response headers of feign with custom key-value pair through custom ResponseInterceptor class.
However, I am facing UnsupportedOperationException due to UnmodifiableMap.

How do we achieve adding custom response headers with minimal code changes to our microservice?

[kdavisk6]

First and foremost, Feign is not a replacement or proxy for real HTTP clients. It's meant to reduce boilerplate and simplify integrations with HTTP-like services, so direct modification of Request and Response internal objects is intentionally difficult.

With that said, you have two options:

• Use a ResponseMapper. This will allow you to mutate the response before decoding, but after intercepting.
• Create a custom Client implementation that decorates the original HTTP Response headers before the internal Response object is created.