What the author ends up proposing, as usual, is basically RPC-over-JSON. Replace JSON with XML and RPC with SOAP, and you get the sort of monster-construct the REST movement was born to fight.
This particular sentence says it all: "the message content should be independent of the transmission channel." That's the RPC dream: no matter what the pipe is, I'm sending you stuff to do. The problem, of course, is that in practice the transmission channel is never neutral: for example, HTTP and RMI are very different beasts, and in practice applications built on top of either one will end up relying on this or that assumption about the protocol, no matter how hard you try to standardize them. Same for any transmission protocol out there, really. You just have to decide when to stop trying to abstract everything away and do your work, because each additional abstraction is inevitably leaky. In this sense, REST basically tells you to stop right there and get to work. REST is not a "transmission channel", it's an application design philosophy for applications built on HTTP. End of.
Pretty much all his other objections can be fixed by using proper response codes and intelligent payloads that do not include verbs. The only verbs you need are in HTTP already - GET, POST and DELETE will cover 99% of your requirements. They make your API substantially predictable and robust. The minute you start putting verbs in payloads, you're doing RPC and you might as well use CORBA. If this is what you want, go ahead and do it, but don't say it's REST's fault if you don't understand what REST is.
> [...] GET, POST and DELETE will cover 99% of your requirements.
Hardly. There's no search in these. You end up putting your query either to
URL, which is hideous, or to request body, which is awful.
The only HTTP verb that can sensibly carry anything beside "create",
"destroy", and "retrieve" commands is POST. This equals to operation
"manipulate". And guess what? Plenty of remote interfaces use at the same
time many operations that can be called "manipulate". Sticking to merely HTTP
verbs is way, way too constraining.
> Hardly. There's no search in these. You end up putting your query either to URL, which is hideous, or to request body, which is awful.
We'll just have to disagree there.
In any case, if you find REST restrictive, fine, go ahead and do your RPC. Just don't try to tell me that it's anything other than RPC, with all the problems and warts we all know.
The value in REST is exactly that it forces you to simplify your interface down to basic verbs that everyone can understand and work with; if you can't do that, if additional complexity is unavoidable, then REST is not for you and you should be aware that your application is now officially complex, maybe too complex to be a public API.
From that point of view, something like SOAP is a perfectly respectable protocol and you should use that instead.
>In any case, if you find REST restrictive, fine, go ahead and do your RPC. Just don't try to tell me that it's anything other than RPC, with all the problems and warts we all know.
Sorry, did Computer Science change the last few years and RPC went out of style?
What "problems and wars we all know" RPC has? Nothing that doesn't go with the field, and isn't already the same (or worse) in REST.
RPC is a basic CS notion that will always be around -- the same way garbage collection, floating point math, functional programming, regular expressions, etc will be.
It not some faulty fad that went away.
>The value in REST is exactly that it forces you to simplify your interface down to basic verbs that everyone can understand and work with
It just forces you to overload HTTP verbs, verbs that people don't use in the first place (even web developers knew and used GET and POST but not PUT and DELETE -- outside of REST and some specialty domains that is), that might or might not match your business logic.
>From that point of view, something like SOAP is a perfectly respectable protocol and you should use that instead.
> [...] fine, go ahead and do your RPC. Just don't try to tell me that it's anything other than RPC, with all the problems and warts we all know.
Why the heck do you think that "lol, you use RPC" would be an insult? Because
you clearly send this message with your tone.
I put RPC wherever I need an operation(s) to be called remotely. And yes, I do
use dedicated RPC protocols (namely, XML-RPC, for popularity of its clients).
I rarely create things that boil down to being a CRUD database interface, so
I find REST very limiting.
> From that point of view, something like SOAP is a perfectly respectable protocol and you should use that instead.
Apparently you haven't worked with SOAP. No, it's not respectable. It's
overcomplicated itself, it uses overcomplicated format (XML with namespaces),
and its tooling is overcomplicated, too (e.g. try to control how WSDL looks
like, so you can swap implementation languages; or try to create WSDL
beforehand, and then implement its backend in a language of your choice).
Really, in HTTP-based remote call protocols (this includes REST!), Microsoft
hit the spot twenty years ago with XML-RPC. The only two things missing are
null/None/undef encoding and named procedure arguments.
> Microsoft hit the spot twenty years ago with XML-RPC.
Well then, why are we even arguing about this? You like pasta, I like pizza, and never the twain shall meet. REST was born out of rejection for XML-RPC (and SOAP, which was its logical evolution once The Enterprise got involved).
If you like XML-RPC, by all means keep using it. I just don't see the point in advocating (as TFA does) that people should abandon working on REST implementations in order to embrace what is basically JSON-RPC, i.e. a completely different thing from a philosophical and design perspective.
(I've ignored the ad-hominems and bad guesses on my work history. Can we keep it civil?)
* SOAP didn't address objects with URIs, so you couldn't integrate your
services with RDF and semantic web; RDF and SemWeb didn't boot very well, so
I wouldn't call it much of a problem today.
* SOAP development was driven by software vendors instead of academics.
This point presumably implies that SOAP and WSDL were a bloated piles of crap
(which SOAP and WSDL are indeed).
* Prescod stated that "mechanism, not policy" results in a more flexible
design, which is funny, because REST is more a policy (architectural style),
with SOAP being now a well-defined, if complex, mechanism.
And now tell me, which of these people are taking into consideration when they
build their REST APIs? I would say none. Most often they simply cram several
operations on several resources, serializing data to JSON and calling it
a day.
>REST was born out of rejection for XML-RPC (and SOAP, which was its logical evolution once The Enterprise got involved).
Not even remotely true. REST was a re-invention of XML-RPC wheel -- for the web and using baroque HTTP conventions that were meant for documents and hyperlinks.
XML-RPC was never rejected because it never caught much on in the first place. On the enterprise they pushed for SOAP at the same time, and on the web it wasn't yet a period were anybody really did rpc (plain AJAX, REST or any other kind).
In terms of simplicity it goes like: XML-RPC -> REST -> abyss -> SOAP, with XML-RPC and REST both on the far "simpler" end of the scale compared to SOAP.
> Not even remotely true. REST was a re-invention of XML-RPC wheel -- for the web and using baroque HTTP conventions that were meant for documents and hyperlinks.
Not even remotely true. REST is an architectural style inspired by the then-existing web, describing an idealized structure based on it, and developed in parallel with and guiding HTTP/1.1. It does not mandate HTTP conventions, though HTTP is itself an example of the style.
REST only involves HTTP conventions to the extent that one decides to use it over HTTP, and only because HTTP involves (obviously) HTTP conventions.
> The only verbs you need are in HTTP already - GET, POST and DELETE will cover 99% of your requirements.
To really do things for arbitrary apps without getting ugly and abusing the intended semantics, you really need at least GET, QUERY (safe, retrieves a resource specified by the combination of the URI and the request body rather than just the URI like GET), POST, PUT, PATCH, and DELETE. All but QUERY and PATCH are very widely supported now, and PATCH is fairly widely supported. QUERY isn't (there are some things like it under various names, mostly overly specific and tied to WebDAV, but nothing general purpose in an RFC or in general use.)
I agree that QUERY would be nice, to disentangle some of GET's workload. PATCH, I honestly don't care for: I'm of the opinion that one should POST (or PUT) and be damned, there are enough codes to specify what the status of the resource was before the action.
>What the author ends up proposing, as usual, is basically RPC-over-JSON. Replace JSON with XML and RPC with SOAP, and you get the sort of monster-construct the REST movement was born to fight.
No, you just get something like XML-RPC. Which was a great and cool solution in its time. Only even simpler in this case, since XML is replaced with JSON.
Nothing to do with SOAP's faults (which were related to over-engineering and ridiculous volumes of specs) at all.
RPC-over-JSON (using HTTP) is exactly what we need and what we want to do.
Only we do it as "REST", complicating our lives trying to condense our endpoints to BS "HTTP verbs" that don't exactly match, and adding a separate off-band lane for status (HTTP STATUS codes) instead of having everything alonside the payload.
> What the author ends up proposing, as usual, is basically RPC-over-JSON [because] "message content/transmission channel."...
No he's not. The RPC pattern is a tad more specific than "any pattern that separates message content from channel". Likewise, just because you put one or more "verbs" in your payload doesn't mean you're doing RPC.
An RPC system has a much more rigid message structure that represents a function call, which is automatically marshaled via concrete client and server methods. If you're just receiving a payload and calling one or more methods based on it's contents, you're not doing RPC and you're not even touching upon any of the problems of SOAP.
The actual problems with SOAP have very little to do with the fact that messages can be serialized or that there are verbs. Here are some of the problems with SOAP:
- XML is verbose, making transmission slower.
- SOAP is a huge, complicated type system compared to JSON.
- Mapping SOAP to a given language is difficult.
- Security concerns over automatic function marshaling.
Meanwhile, you can write a JSON parser in an afternoon and it's extremely simple idioms are relatively easy to relate to a given programming language.
About all I gleaned from reading it was a big list of reasons why 'RESTful' is bad, and that the main solution was to use HTTP(s) as purely a transport layer.
What, exactly the 'solution' will look like depends on future posts... however https://xkcd.com/927/ (Standards) comes to mind.
Is it so strange? XML-RPC is simpler ancestor of SOAP. JSON-RPC is a superset
of XML-RPC (includes e.g. named parameters), defined over JSON instead of XML.
JSON-RPC doesn't have the wide spread of XML-RPC, though.
I don't see much wrong with those, and they do much better than REST, since
they already have well-defined way of signaling errors.
This particular sentence says it all: "the message content should be independent of the transmission channel." That's the RPC dream: no matter what the pipe is, I'm sending you stuff to do. The problem, of course, is that in practice the transmission channel is never neutral: for example, HTTP and RMI are very different beasts, and in practice applications built on top of either one will end up relying on this or that assumption about the protocol, no matter how hard you try to standardize them. Same for any transmission protocol out there, really. You just have to decide when to stop trying to abstract everything away and do your work, because each additional abstraction is inevitably leaky. In this sense, REST basically tells you to stop right there and get to work. REST is not a "transmission channel", it's an application design philosophy for applications built on HTTP. End of.
Pretty much all his other objections can be fixed by using proper response codes and intelligent payloads that do not include verbs. The only verbs you need are in HTTP already - GET, POST and DELETE will cover 99% of your requirements. They make your API substantially predictable and robust. The minute you start putting verbs in payloads, you're doing RPC and you might as well use CORBA. If this is what you want, go ahead and do it, but don't say it's REST's fault if you don't understand what REST is.