Affects: 6.1.6

I have an API that requires sending a Content-Length: 0 when the body is null/empty.

When we previously upgraded to Spring Boot 3 / Spring 6, we changed our RestTemplate to use new BufferingClientHttpRequestFactory(new HttpComponentsClientHttpRequestFactory()) as the request factory in order to ensure that a Content-Length was set.

This worked on 6.1.5, but on upgrading to 6.1.6 we are no longer sending the Content-Length header.

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Stepping through the code with a debugger, this changed in 019ce44 / gh-32612.

I can force the old behavior if I do the following, which leads me to believe it is that commit (effectively, I'm trying to just skip over the new if):

• Set a breakpoint at line 58 and at line 59 of BufferingClientHttpRequestWrapper
• (on line 58 breakpoint) in the evaluation expression window run bufferedOutput = new byte[1];
• Continue to line 59 breakpoint
• (on line 59 breakpoint) in the evaluation expression window run bufferedOutput = new byte[0];

Doing this then causes the Content-Length: 0 header to be sent as expected.

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I tried also manually setting Content-Length: 0 as a header, but HttpComponentsClientHttpRequest does not allow that, as is explicitly ignores Content-Length as a header.

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This still works as expected (Content-Length: 0 is set) when using SimpleClientHttpRequestFactory, so for now I can work around this by using new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory()) instead. However, I would prefer to use HttpComponentsClientHttpRequestFactory instead of Simple if possible.