Optional headers with an empty value are converted to the empty string

[DoronShapiro]

What happened?

I have an endpoint method with an optional argument annotated by @HeaderParam:

@GET
@Path("/doStuff")
String doStuff(@HeaderParam("value") Optional<String> value);

I passed it the value Optional.empty() via a JaxRsClient:

MyService service = JaxRsClient.create(...
service.doStuff(Optional.empty())

However, the implementation of doStuff receives the value Optional.of(""), rather than Optional.empty().

There is a failing test case to show this at develop...DoronShapiro:optional-header-tests.

This behavior happens because the implementation of Java8OptionalAwareContract serializes empty headers as an empty string, but when they are deserialized by the Java8OptionalParamConverterProvider, it is assumed that the value will be null if empty (and that the empty string represents a non-empty value).

What did you want to happen?

The server should receive a value of Optional.empty() for the header argument.

One solution is for the client to not include the header at all if its value is Optional.empty().

[stale]

This issue has been automatically marked as stale because it has not been touched in the last 60 days. Please comment if you'd like to keep it open, otherwise it'll be closed in 7 days time.

[iamdanfox]

I think this is still a valid bug - keep open!

[stale]

This issue has been automatically marked as stale because it has not been touched in the last 60 days. Please comment if you'd like to keep it open, otherwise it'll be closed in 7 days time.

[uschi2000]

keep open

[stale]

This issue has been automatically marked as stale because it has not been touched in the last 60 days. Please comment if you'd like to keep it open, otherwise it'll be closed in 7 days time.

[pkoenig10]

This is pretty easy to fix, but requires upgrading Feign to get OpenFeign/feign#724.