In case a manually implemented controller is registered to add a dedicated media type for a Spring Data REST resource (e.g. an HTML representation for item resources) we now continue to serve JSON in case the request indicates it wants to see it.
Previously this didn't work as the manually implemented controller method was detected to partially match (only the produces-clause not matching) and thus an exception being thrown from the HandlerMapping lookup. This caused the HandlerMapping registered for repositories not being considered at all.
This is now fixed by hiding the HandlerMapping instances we register behind a DelegatingHandlerMapping that continues to try delegates even in a case of an exception being caused in a particular resolution attempt. Should all resolution attempts fail, we then throw the original exception if one occurred in the first place.
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