I´m trying to design a REST API for my application and I read a lot about best practices and how REST is supposed to work. One of the most important topics about REST is, that the resources should be linked via references and the client should only know the root URL of the API.
But I cannot find any API documentation that really does this. Every REST API documentation I ever read on the web shows an exact description of the URLs of the possible endpoints.
Is there any API documentation out there that only shows the root URL and describes how to navigate through the resources?
One of the most important topics about REST is, that the resources should be linked via references and the client should only know the root URL of the API.
The root URL and the media types, yes. The client needs to know where to start, and also how to interpret the responses it gets.
Your primary example of a REST API would be the world wide web. You point your browser at www.google.com, and then you just follow links and submit forms until you get the result you want.
Another REST API that might be familiar is Atom Syndication / Atom Pub.
More academically, there is RESTBucks. That paper was somewhat popular, and you can find a number of sample implementations around.
Jon Moore (2011) presented a good demonstration of a hypermedia API.
Every REST API documentation I ever read on the web shows an exact description of the URLs of the possible endpoints.
Yes; bad examples are much more common than good examples.
I'm new to this game so I might be misunderstanding things. Actually, if someone tells me that I'm misunderstanding things, it will be a favor. Maybe this person will be considerate enough to show me the right path. But...
One of the "guidelines" or "best practices" of REST as it applies to Web Services (http://en.wikipedia.org/wiki/Representational_state_transfer#Applied_to_web_services) is that you should use the proper HTTP methods when making calls (did I misunderstand it?) to REST API's.
But looking at many API implementations on the web, what I see is that 100% of the calls made to them are actually GET calls that, depending on their URI, will be interpreted by the API as being of one of the HTTP verbs or methods.
So, for example, looking at the REST API documentation for Twitter (https://dev.twitter.com/rest/public) which, in principle, only defines two verbs/methods (GET and POST), actually have all calls sent as GET and, based on the URI in the GET call, are interpreted by the API and acted upon.
Example:
GET statuses/lookup: https://api.twitter.com/1.1/statuses/lookup.json
POST statuses/update (PUT?): https://api.twitter.com/1.1/statuses/update.json
In both cases, the call itself was made using GET and the last part of the URI defined it as a real GET or as a POST.
In summary, to be truly RESTful, shouldn't client side implementations of REST API's for web services use the proper HTTP verbs/methods?
What am I missing?
You're missing a lot, but don't worry about it, most people are.
The fact is that very few so-called REST APIs publicly available on the internet are really RESTful, mostly because they are not hypertext driven. REST became a buzzword to refer to any HTTP API that isn't SOAP, so don't expect for an API to really be RESTful just because it says it's a REST API. I recommend reading this answer.
From my experience, most API developers aren't aware what REST really is and believe any HTTP API that uses HTTP and avoids verbs in URIs is REST.
REST is defined by a set of constraints. Among them is the uniform interface, which in simple terms means that you should not change the expected behavior of the underlying protocol. REST isn't coupled to any particular protocol, but since it's common to be used with HTTP, they get convoluted sometimes.
HTTP has very well defined semantics for the GET, POST, PUT, DELETE, PATCH and HEAD methods, and the POST method has its semantics determined by the server. Ideally, a REST API should respond to the methods other than POST exactly as determined in the RFC 7231, but as you noticed, there are many APIs who call themselves REST but don't do that. This happens for many reasons. Sometimes there's a simple misunderstanding about the correct semantics, or it's done to keep consistency, or because of backwards compatibility with intermediaries that don't support all methods, and many other reasons.
So, there's a lot more that has to be done to be truly RESTful other than using the HTTP methods correctly. If an API doesn't get even that right, it needs to find another buzzword, because it's definitely not REST.
I can't exactly tell what your question is, but I believe there are some concepts that will help you. Allow me to elaborate...
You are correct that many APIs use a limited number of HTTP "verbs" in their API. GET/POST are the most common. PUT less so, and then all others (DELETE, HEAD, OPTIONS etc) are used with vanishing probabilities.
Dropbox Core API for file uploads allows optional PUT / POST and their stated reason is "For compatibility with browser environments, the POST HTTP method is also recognized."
Indeed the limitation is the browser. Popular web servers have no problem with all HTTP request methods and even made up ones. After all, the request method is just some string with regard to the web server.
HTML4 and HTML5 only allow GET and POST requests for form requests. If you want your API to be used through a browser at all - and hey why not, it sounds like a useful thing - then you're limited to GET/POST. For a useful discussion on this see: https://softwareengineering.stackexchange.com/questions/114156/why-are-there-are-no-put-and-delete-methods-on-html-forms
Further complicating things is the fact that REST is not an industry standard. There exists no RFC, ISO or other document detailing what a "compliant" implementation must and must not do. While many folks have been playing concepts related to REST for some time, the REST concept was "invented" in the PhD disseration of Roy Fielding. A fantastic read if you're interested in such things.
Yes, according to REST, APIs should be using the correct verbs. However, as long as the documentation is clear and all GET requests are idempotent, then life should continue smoothly.
(Source: I wrote PipeThru.com which integrates 40+ APIs, Dropbox and Twitter included)
I think that this link could give you some hints about the design of RESTful services / Web API: https://templth.wordpress.com/2014/12/15/designing-a-web-api/.
It's clear that not all Web services that claim to be RESTful are really RESTful ;-)
To be short, RESTful services should leverage HTTP methods for what they are designed for:
method GET: return the state of a resource
method POST: execute an action (creation of an element in a resource list, ...)
method PUT: update the complete state of a resource
method PATCH: update partially the state of a resource
method DELETE: delete a resource
You need to be also to be aware that they can apply at different levels, so methods won't do the same things:
a list resource (for example, path /elements)
an element resource (for example, path /elements/{elementid})
a field of an element resource (for example, path elements/{elementid}/fieldname). This is convenient to manage field values with multiple cardinality. You don't have to send the complete value of the fields (whole list) but add / remove elements from it.
Another important thing is to leverage HTTP headers. For example, the header Accept for content negotiation...
I find the Web API of Github well designed and its documentation is also great. You could browse it to make you an idea. See its documentation here: https://developer.github.com/v3/.
Hope it helps you,
Thierry
You are correct. If they want to be "RESTful", their API should respect the semantics of each HTTP method.
Roughly, REST is about method Information (what the server should do), scoping information (where the server should do it) and, I almost forgot to mention, hypermedia driven (make sure you check #PedroWerneck's great answer to this question as it talks about it a little more and referecences a blog post from Fielding on the matter).
What the API you mentioned does is have both method and scoping information in the URL. That would not fit the RESTful architecture very well, as it, in general terms, tells us to:
1) use the HTTP methods the proper way (respecting their properties, such as idempotency and others), and
2) use unique URIs to identify unique resources.
Point 1 says "use HTTP methods to convey method information" and point 2 says "use URIs to convey scoping information".
Again, if an API uses GET with a specific parameter in the URI to do something (and not get something), then it is using URI to convey method information.
Now, don't be alarmed. Most APIs out there are just RESTful-ish (like twitter's of flickr's), meaning they are an animal between REST and something else. That is not bad per se, it just means they will not fully benefit from what RESTful architectures (and HTTP) have to offer.
Remember that being RESTful isn't just a matter of fashion, it does have its benefits, such as statelesness, adressability, and so on. And those can only be fully achieved by using the HTTP verbs like they were supposed to be used.
About using POST instead of PUT, considering they have different properties (PUT is idempotent, POST is not), it is not bad to use POST, as long as it is uniformly designed, that is, a programmer should not wonder what POST will do for each and every URI in the API: they all should behave the same. (PUT does not suffer from that because it already is uniform.) I talked a little more about this - and quoted Roy Fielding's say on it - in another question (check out the "Wrapping Up" part).
Consider looking at REST Richardson Maturity Model topic.
This specification is about how much RESTful particular API is:
Level 0:
Simple GET and POST request to descriptive url
/getUserByName?name=Greg
Level 1:
Divide all content in resources and define actions in resource group
/user/getByName?name=Greg
Level 2:
Proper use of HTTP verbs.
GET /user/Greg
Level 3:
Use hypermedia controls
Different APIs in interent implement different maturity level of REST. That's why some APIs don't support all HTTP features.
I primarily deal with REST json APIs at my work. So I am familiar with them. But for my own project I am trying out app engine as I believe it is a great fit.
I had already started writing my logic in python (using ferris), and in reading more on app engine I came across protorpc and cloud endpoints. But in most of the examples I have read, they seem to be doing the same just as I would do in a rest api. Make a request with json, and get a json response back. Or an error.
The main difference I see, is that in rest, the endpoints are based around a resource. And the HTTP verbs around them such as GET, POST, PUT, DELETE, etc. Where as in RPC, each request would have it's own endpoint rather than be based around a resource or model.
Both are requested with, and respond with json. So I think I am failing to see the benefit of using Google endpoints. Do they offer some other kind of benefit? I could maybe see better analytics tracking with endpoints. But wouldn't I still need to the use post http verb for modifying content?
Would any of this change if I was using certain frameworks? Like django. Although I am currently testing out Ferris which has a messaging system that deals with protorpc. Although, I have not been able to rest or yet.
So what am I missing? What are the benefits of endpoints over just making my object methods handle a json request. Do socket connections play into this at all?
You can do both by using endpoints to make a RESTful API.
protorpc/endpoints doesn't magically make your API RESTful. You have to make your API RESTful within the endpoints framework, which uses protorpc.
The benefits of using endpoints is that you can get a lot of the authentication work done easily (assuming you're going to use Google accounts), the serialization/deserialization is done for you, your client libraries can be generated for you, and more than just a Javascript client can be supported. If these things sound good, endpoints may be right for you. If these things don't apply, then maybe be more direct and use RequestHandlers yourself.
I was able to make a simple API using endpoints. It has 3 main resources: records, datasets and moves. A Record object is the smallest unit of data. The Dataset object is a group of records. And the Move object represents the event of a Dataset changing location.
My RESTful URIs look like this:
GET /records # Get list of records
GET /records/<id> # Get single record
POST /records # Create records
GET /datasets # Get list of datasets
GET /datasets/<id> # Get single dataset
POST /datasets # Create dataset
GET /moves # Get list of moves
GET /moves/<id> # Get single move
POST /moves # Create move
With this I can create data, organize it and move it around. I was able to do this completely within the endpoints framework on App Engine and it is RESTful.
Rest confuses me sometimes. I know that it involves creating an API layer over your data and then you make calls to that data through the API. The best way I think of Rest is that the actual Twitter website interfaces with the data-layer through API calls.
That made me wonder then: Is a backend-service like Parse also a Rest API to your data?
What might be the difference between Parse and say, building your own Rest API like this guy did: http://coenraets.org/blog/2012/10/nodecellar-sample-application-with-backbone-js-twitter-bootstrap-node-js-express-and-mongodb/ (he's getting some solid google rankings for his API tutorials).
A simple yes/no might answer the question, but providing details will really be appreciated.
I look forward to the answers.
Parse is built around a restful API just like most, if not all, other mBaaS out there.
A RESTful Api isn't just CRUD operations though nor is it the same thing as Parse. Parse is a company that provides a remote backend to developers using a RESTful api.
RESTful api !== BaaS
I have dealt with about 5 mBaaS and Parse isn't really one of them, but I've glanced at their API reference for JS and I think they use mongodb clusters. An mBaaS usually provides the developer the ability to have cloud storage, push notifications, server side code, easier social media integration, and mobile analytics. So it's not just any backend. Although there are some mBaaS, like Urban Airship, that only supply push notifications to developers.
A RESTful api at it's core usually has some key functions that are centered/wrapped around an httpRequest
They usually use "GET", "POST", "DELETE", and "PUT" to make all calls. Some allow the implementation of rpc for custom server logic. An mBaaS takes a lot of work to implement right and well. You can't build Parse in a Day. It takes a lot of planning and such. The differences between Parse and that guy in link are in the implementation, range of features, and purpose in general(the audience).
To better understand REST maybe look here you can also read the HTTP spec if you are feeling adventurous.
What things should a developer designing and implementing an API for a community based website know before starting the heavy coding? There are a bunch of APIs out there like Twitter API, Facebook API, Flickr API, etc which are all good examples. But how would you build your own API?
What technologies would you use? I think it's a good idea to use REST-like interface so that the API is accessible from different platforms/clients/browsers/command line tools (like curl). Am I right? I know that all the principles of web development should be met like caching, availability, scalability, security, protection against potential DOS attacks, validation, etc. And when it comes to APIs some of the most important things are backward compatibility and documentation. Am I missing something?
On the other hand, thinking from user's point of view (I mean the developer who is going to use your API), what would you look for in an API? Good documentation? Lots of code samples?
This question was inspired by Joel Coehoorn's question "What should a developer know before building a public web site?".
This question is a community wiki, so I hope you will help me put in one place all the things that should be addressed when building an API for a community based website.
If you really want to define a REST api, then do the following:
forget all technology issues other than HTTP and media types.
Identify the major use cases where a client will interact with the API
Write client code that perform those "use cases" against a hypothetical HTTP server. The only information that client should start with is the response from a GET request to the root API url. The client should identify the media-type of the response from the HTTP content-type header and it should parse the response. That response should contain links to other resources that allow the client to perform all of the APIs required operations.
When creating a REST api it is easier to think of it as a "user interface" for a machine rather than exposing an object model or process model. Imagine the machine navigating the api programmatically by retrieving a response, following a link, processing the response and following the next link. The client should never construct a URL based on its knowledge of how the server organizes resources.
How those links are formatted and identified is critical. The most important decision you will make in defining a REST API is your choice of media types. You either need to find standard ways of representing that link information (think Atom, microformats, atom link-relations, Html5 link relations) or if you have specialized needs and you don't need really wide reach to many clients, then you could create your own media-types.
Document how those media types are structured and what links/link-relations they may contain. Specific information about media types is critical to the client. Having a server return Content-Type:application/xml is useless to a client if it wants to do anything more than parse the response. The client cannot know what is contained in a response of type application/xml. Some people do believe you can use XML schema to define this but there are several disadvantages to this and it violates the REST "self-descriptive message" constraint.
Remember that what the URL looks like has absolutely no bearing on how the client should operate. The only exception to this, is that a media type may specify the use of templated URIs and may define parameters of those templates. The structure of the URL will become significant when it comes to choosing a server side framework. The server controls the URL structure, the client should not care. However, do not let the server side framework dictate how the client interacts with the API and be very cautious about choosing a framework that requires you to change your API. HTTP should be the only constraint regarding the client/server interaction.