Created a small refactoring for gh-25109.

Changed:

  1. Field duplication
  2. Set DefaultBodyBuilder as protected, to allow children from other packages to call constructor (it seemed very constrictive to allow the call of the contructor only from the existing package)
  3. Moved the 
Assert.notNull(method, "HttpMethod is required. If testing a custom HTTP method, " +
                    "please use the variant that accepts a String based HTTP method.");

to DefaultBodyContructor to also catch the contructor call 

public static BodyBuilder method(HttpMethod method, URI url) {
        return new DefaultBodyBuilder(method, url);
    }

to leave the main constructor easier to understand and failfast when constructing he builder. Also, messages when calling the 

MockServerHttpRequest.method(null, *any URI*)

would have failed with another kind of assertion message than 

MockServerHttpRequest.method(null, urlTemplate, param1, param2)
  1. Extended the check for the string value of HttpMethod to exclude the set of HttpMethod to only whitespaces, as this, imho, makes no sense

Comment From: midumitrescu

Hey Rosen (@rstoyanchev ),

would you please mind taking a short look if this makes any sense to you?

I could also create some small unit tests to make sure that the failure message is the same when HttpMethod null is set, but I think this is not that valuable

Comment From: midumitrescu

Quick question, sorry for asking this.

There is another MockServerHttpRequest in

org.springframework.web.testfixture.http.server.reactive.MockServerHttpRequest

Is that auto generated or should it also receive this functionality ?

Comment From: sbrannen

There is another MockServerHttpRequest in

You will need to manually copy the changes to that class to keep them in sync.

Comment From: midumitrescu

There is another MockServerHttpRequest in

You will need to manually copy the changes to that class to keep them in sync.

Done