Added FeignRequestException, FeignResponseException

[finke-ba]

Idea was to use two different classes for holding Request and Response objects.

Couple of moments that I'm not sure about:

1. Add request object to RetryableException and to errorExecuting method.
2. In FeignResponseException I'm copying response body to another input stream due to root input stream already closed on the moment of handling exception.
3. I deleted the response body from the message variable what makes this commit back incompatible.
4. Test added put in correct place/class.

I'm looking forward to questions and comments.

Fixes #642

[kdavisk6]

The only difference between FeignRequestException and FeignResponseException is the inclusion of a body attribute. I would reconsider this approach. If the intent is to make the body available, we can add a body attribute to FeignException and get the same result, without the cascading changes.

Can you give that a try?

[kdavisk6]

See my comments

[finke-ba]

@kdavisk6 Thanks for comment!
The main idea to create two additional exceptions was to have Request and Response object in Exception class. It gives more flexibility instead of adding just a body. Maybe it's already too much.
But please check carefully comments for this PR #664 first, because I used the ideas from that.

[kdavisk6]

The notions of Request and Response are abstractions that are within OpenFeign. User's of the library are defining interfaces, with methods, not Requests and Responses. By exposing those abstractions through FeignException, we are leaking those out to users, requiring them to at least be aware of those abstractions and how to work with them. This is the definition of Leaky Abstractions, and it's something we should strive to avoid.

The original issue (#642), indicated that a separate field, with the appropriate body, would be sufficient, and I agree. Another suggestion that might clear this up is to not call the field body, but instead call it details or something else. body or RequestBody is another abstraction we should avoid leaking.

User's can then inspect the Exception details for additional information.

[finke-ba]

Ok, that sounds reasonable. I'll create another implementation with one additional attribute in FeignException .

[finke-ba]

@kdavisk6 , hello!
Please check my update.

[kdavisk6]

Thank your making these changes.

[kdavisk6]

If there are no more comments in the next few days, I will accept this change.

[finke-ba]

That is awesome.
@kdavisk6 thank you a lot for your help!