Prior to this commit, the various `HttpMessageConverter` instances
configured for a given `RestTemplate` instance could all contribute
`MediaType` values to the "Accept:" request header.
This could lead to duplicate media types in that request header,
cluttering for the HTTP request for no reason.
This commit ensures that only distinct values are added to the request.
Issue: SPR-16690
Closes gh-22401
Commit #93b7a4 added support for pre-configuring URI variables at the
UriComponentsBuilder level, and also changed toUriString to encode
template and URI variables separately. However this went a bit too far
causing side effects for URLs with curly braces that don't represent
URI variables.
This commit restores the original toUriString behavior which is to
encode template and URI variables sepraately only if URI variables have
been pre-configured.
Issue: SPR-17630
Prior to this commit, when errors happened before the response was
committed, the `Content-Length` response header would be left as is.
This can be problematic since the error can be handled later in the
chain and the response body changed accordingly. For example, Spring
Boot renders error pages in those cases. If the `Content-Length` is set,
HTTP clients can get confused and only consider part of the error
response body.
This commit ensures that any `Content-Length` response header is removed
in case of errors, if the response is not already committed.
This is done at the `AbstractServerHttpResponse` level, since errors can
be handled in multiple places and the response itself is the safest
place to handle this case.
As a consequence, this commit also removes `Content-Length` checks in
`EncoderHttpMessageWriter` since we now consider that we should rely on
the response body we're about to write rather than any previously set
value.
Issue: SPR-17502
(Cherry-picked from 3203d39821)
Review and update Servlet and Undertow adapters to release any data
buffers they be holding on to at the time of error or cancellation.
Also remove onDiscard hooks from Reactor and Undertow request body.
For Reactor we expect it to be handled. For Undertow there isn't
any Reactor Core upstream for the callback to be useful.
Issue: SPR-17410
Prior to this commit, an bug introduced in SPR-16949 prevented
`Mono.empty` bodies from being written to the response.
This commit ensures that empty bodies still trigger the writing to the
response and does not hang the processing of the exchange.
Issue: SPR-17220
Cherry-picked from: 280da61d5c
