Polish resolveArgument method in RequestResponseBodyMethodProcessor

[shin-mallang]

String name = Conventions.getVariableNameForParameter(parameter);

The above code is only used in conditional statements.
So I moved it into the conditional statements.
With this, we can expect a slight performance improvement in some case.

[shin-mallang]

and I was wondering if there are any situations where binderFactory is null.
If you don't mind, could you let me know?

[sdeleuze]

I merged this refinement. For your question, I am not sure how common it is, maybe @poutsma or @rstoyanchev know more.

[shin-mallang]

@sdeleuze
thank you :)