What is the problem with hard-coded URLs? It is certainly simpler than having to extract the URLs from some other request. If they don't change (and they shouldn't!) I don't see the problem.
I tend to like APIs with small surface areas because it means I don't have to drag along outdated endpoints across minor versions because the org doesn't want to v2 anything. URLs as an implementation detail makes backwards compatibility much easier. So many times it's been useful to combine or split endpoints as the business needs change without affecting clients.
The worst part about using HATEOAS for me has been clients who are used to constructing URLs continue to do so and create a ticket where the obvious first question is "Are you constructing that URL?"
So this gives you only the freedom to change the URL naming scheme, but if you want to change the functionality in any way that's not 100% compatible, you still have to drag along outdated endpoints with the old functionality or you'll break clients.
But this goes so much in contrast to your comment that it seems that I'm probably misunderstanding you - can you give an illustrative example on how exactly does this allow you to combine or split endpoints without affecting client software that sends/takes data from those endpoints and does some action (business logic) based on that data?
[1] https://blog.ploeh.dk/2013/05/01/rest-lesson-learned-avoid-h...
> In the future, I plan to make URLs opaque when building level 3 APIs. Instead of http://foo.ploeh.dk/customers/1234/orders, I'm going to make it http://foo.ploeh.dk/DC884298C70C41798ABE9052DC69CAEE .... Obviously, that means that my API will have to maintain some sort of two-way lookup table that can map DC884298C70C41798ABE9052DC69CAEE to a request for customer 1234's orders
I pity the people who had to work with him, and the many thousands of hours this has probably ended up costing.
Strictly speaking, you're wrong: a URL specifies a location of the resource, and a mechanism for retrieving it. If the location of the resource changes, so would a URL.
Even without this philosophical argument, there is an actual practical issue that URLs do change all the time. Both HATEOAS and Persistent URLs are mechanisms to cope with that: HATEOAS proposes to write clients that instead of using hardcoded URLs would use late-bound URLs supplied by the origin server; PURL proposes to hide the origin server behind a proxy that would translate hardcoded URLs used by the clients to the current scheme and either proxy or redirect the requests.
The main problem with either solution is that URLs use domain names as their "authority" part, so whenever you lose control of the old domain, the "entry point" URL has to change and there is nothing much you can do about it.
Yes, I know that URLs (URNs, actually, IIRC) were supposed to be immutable and eternal, with redirects set up (and maintained somehow, by someone, forever) to point to the current locations, but that didn't work out for obvious reasons.
I still don't see any reasonable scenario where an API would change the (site-relative) URL's without also changing the semantics of the API. And if the semantics change you would have to rewrite the client anyway.
In any case, if you change the URL's without changing the semantics you should respond 301 on the old URL, so even a client with hardcoded URL's would work correctly without the need for HATEOAS.
You force your users through garbage you get support tickets like that. Instead of blaming the users, think why your great approach is actually problematic for them.
The single entry point has no benefits unless the api is multi-company, no one specifically hosts it. Is this the case? If no, your hateoas and single url approach is pure cargo cult.
> It is certainly simpler than having to extract the URLs from some other request.
It's not extracted from other request, it's extracted from the response to the original request, and using a field from the local struct is not harder than using a global constant.
Well they shouldn't! And if the API arbitrarily changes URLs around without reason, then surely they might also change the URL for the initial request.
If you treat them as public interface, they shouldn't, yes. But if you treat them as internal implementation details, they absolutely could.
One can also think about it as static vs dynamic dispatch: you make an initial request, you get a vtable of "method name -> method pointer" as a part of response. Or you can hardcode the method pointers and make it the remote server's job to properly chose the appropriate internal endpoint.
If they have “all the info they need”, they have the identity of Y, which in a system designed around REST is the URL, and if Y is a resource, then its URL is the URL for actions on it, and the type of thing it is will tell you what method to use and (where one is applicable) resource to send to accomplish the action.
HATEOAS is more than just shipping URLs.