I'm thinking of using RailwayJS to build my web server. Previously I was using express, which is considered to be RESTful. However, from what I've been reading, it seems that RailwayJS is not considered to be RESTful, even though it uses express!
What is it about RailwayJS that makes it not RESTful? If it passes messages using JSON doesn't that make it RESTful?
I'm curious where and/or how you drew your conclusions regarding REST and Express/RailwayJS?
Express allows you the freedom to set up your router any way you wish; you could very easily create a very RESTful style application, or you could very easily break every rule in the REST architecture. Express presents no opinion on you whatsoever.
RailwayJS, however, seems to favor a more RESTful style interface--at least, when using "REST" in the same context as you would in, say, Ruby on Rails. Railway supports resource based routing, which maps a resource to seven very Rails-like URLs/HTTP verbs:
Resource-based routing provides standard mapping between HTTP verbs and controller actions:
map.resources('posts');
will provide following routes:
helper | method | path | controller#action
---------------------------------------------------------------
posts GET /posts posts#index
posts POST /posts posts#create
new_post GET /posts/new posts#new
edit_post GET /posts/:id/edit posts#edit
post DELETE /posts/:id posts#destroy
post PUT /posts/:id posts#update
post GET /posts/:id posts#show
Thus my conclusion would be, when using "REST" in the context that most people do when designing MVC-based web applications, that Express can be RESTful, depending on how you design your app, but isn't inherently RESTful, and that RailwayJS prefers a RESTful setup (although you don't have to use resource-based routing in RailwayJS either).
Related
may I have some example/typical use case of HATEOAS? I agree it can be a very powerful concept provide great flexibility but I am not sure how to properly get benefit from HATEOAS. would be great if you can share your experience/use case.
A good answer from #dreamer above, but HATEOAS is not present in most REST-based services. It is a constraint on the REST architecture style that allows clients to interact with a service entirely via the hypermedia contained in the resources.
If you look at the Twitter or Facebook REST APIs, you won't find hypermedia. Look at the Facebook friendlist resource. There are no hypertext links in that resource that you can use to transition the state of the resource - to delete, update, etc. Instead, you need to read the out-of-band documentation to understand what you need to do to delete that resource.
One of the claimed advantages of using hypermedia in your APIs is that you can manage change within the resources themselves. For example, what if Facebook wanted to add additional functionality to the frendlist? If it were built with HATEOAS in mind, the resource would be updated to add the hyperlinks provides those additional state transitions.
If this sounds difficult, you're right. But as a developer of client applications, however, once you understand how the hypermedia is presented, you can build applications that will evolve along with the API itself.
So how do you build APIs using HATEOAS? A number of options are out there, but I like the Hypertext Application Language (HAL) the best.
UPDATE: Since you asked for an example, here's a link to a demo using HAL.
Good public HATEOAS use cases are hard to find, because there are a lot of misconceptions around REST, and HATEOAS can be hard to implement. You really need to have a good understanding of its benefits, before you're willing to put yourself through the trouble of getting it to work, and if the clients don't follow it correctly, all work will be in vain.
From my experience, implementing proper REST in a company is a culture change as important as moving to version control systems or agile development. Unless everyone adopts it and understands it, it causes more trouble than it solves.
Having that in mind, I think the best example one will find is the foxycart.com HAL API, on the link below:
https://api-sandbox.foxycart.com/hal-browser/hal_browser.html#/
It's very powerful concept used in RESTful presentation of the application to the client. There are many many projects which are adopting this interface now. A typical use case for this is Web Services APIs using RESTful APIs. A RESTful APIs typically consists of the following elements:
base URI, such as http://example.com/resources/
an Internet media type for the data. This is often JSON but can be any other valid Internet media type (e.g. XML, Atom, microformats, images, etc.)
standard HTTP methods (e.g., GET, PUT, POST, or DELETE)
hypertext links to reference state
hypertext links to reference related resources
The application state can be modified using above HTTP methods for example, to get a particular resource, A client can issue a REST query using curl like:
curl -X GET --url "http://example.com/resource/" -X "Content-Type:application/json"
you could go through the man pages for curl and its usage. More on RESTful interface concepts can be looked upon at wiki
Thanks for looking!
Background
I am building a strictly machine-to-machine web-service (restful) application. The application will listen for requests, retrieve data, construct objects, serialize to JSON and return the JSON object.
This application will ultimately be used by other web applications as well as iOS apps, Android apps, and even desktop apps.
The existing code that I have inherited makes a distinction based on how the service was called in terms of HTTP verbs (GET, POST, etc).
Question
In this day and age of machine-to-machine communication, is the HTTP verb even relevant any longer? Could it in fact be constraining for future adoption of the service API to base the code around HTTP verbs?
Update
fmgp provides a clear answer to "why" these verbs are used, but I feel should I clarify my concern:
Will other platforms such as iOS or Android (for example) be able to originate HTTP verb-based calls like GET and POST? If the answer is "no" then I assume that we should stay away from relying on these verbs and instead build the desired action into the request URL as a parameter.
In RestFul applications, you have a verb foreach CRUD operation:
Create: POST
Read: GET
Update: PUT
Delete: DELETE
Everything claimed "restful" will work the same way according to this philosophy.
There's nothing standard in that, just a clean, good designed, easy to understand programming style. Of course you may want to do all operation with only GET and some query parameters as soon as your client and server can handle it.
I was wondering what would be the best approach to make a Grails app offer a RESTful API (some CRUD actions mainly) that can be used by a web service, e.g. when you want to build a corresponding iOS app to your browser-based app or anything else.
I thought of building a separate part in my Grails application that takes calls from www.mywebapp.com/api/someAction so that I can reuse the Service layer. How would I do the URL mapping then? Only having one big ApiController does not sound very groovy.
Or is there any better approach I did not know of? This approach must support something like OAuth to authenticate the user who is calling the Web service.
Grails can definitely provide a REST api, but the level of difficulty in doing so varies depending on how mature (aka. how RESTful) you want the API to be.
Basic REST
Getting a basic level of RESTfullness, where you are manipulating json or xml representations of resources using the full span of HTTP verbs and leveraging the HTTP response codes, is pretty easy. There are 3 main pieces to getting that in place:
URL mapping
Here's an example of how I wrote my URL mappings on a recent project to allow for more RESTful URLs:
// RESTful list mapping
name restEntityList: "/$controller"(parseRequest: true) {
action = [GET: "list", POST: "save"]
}
// RESTful entity mapping
name restEntity: "/$controller/$id"(parseRequest: true) {
action = [GET: "show", PUT: "update", POST: "update", DELETE: "delete"]
constraints {
id matches: /\d+/
}
}
Content negotiation
The 3 different ways that Grails can handle content negotiation make the framework very flexible, allowing you to support a much broader range of clients who may not be able to set things like the Accept HTTP header.
You can use the content negotiation to respond to different requests in different ways using the withFormat block based on what the client has indicated they want. This powerful ability can also be used to version your API, much like how Github does.
Response status
HTTP already has a great response mechanism built into it that allows you to leverage innate abilities in the architecture, like cacheability and indemnipotent operations. While some web browsers don't handle certain response codes very gracefully, client applications using your API can use them to greatly simplify their internal code.
DRY REST
One of the best ways to make your application RESTful and keep it DRY at the same time is to leverage the controller scaffolding as much as possible, since CRUD is essentially the same for all domain objects. This article on making the default controller more RESTful, and this article on simplifying the default controller are both great resources for getting more power from the scaffolding.
Advanced REST
Once you get to that point, you have a pretty functional REST API for your grails application. You can do all basic CRUD operations and the resources are fairly easy to work with.
The next levels of the ladder to a true RESTful hypermedia API, however, are much harder to attain. Fixing this is on the road map for Grails, but currently it's rather painful. These pieces are:
Hypermedia resources
Content types
Versioning
Thankfully, there is a plugin that makes defining custom marshallers very easy, which allows us to fairly easily cover those three remaining pieces of the REST puzzle.
Finally, there is the aspect of securing the whole thing. In general, Spring Security will hold you in good stead as far as securing user-access to your api. Since most API access is from an application, and isn't user-visible, basic or digest authentication is usually the simplest way to go. There is an OAuth plugin that builds on Spring Security. I have not personally used it so I can't vouch for it's stability, but it looks pretty good to me.
In general, Grails is flexible and powerful enough to do REST very, very well, but the work has not been done yet to make it do REST cleanly out-of-the-box.
the grails documentation has a good walk though on setting up a RESTfull api
http://grails.org/doc/latest/guide/webServices.html#13.1
You can map it anyway, use any url structure. Grails UrlMapping is pretty flexible, it's only default behavior to map to /$controller/$action, but you can use your own mapping, you can event map each url manually, etc.
See UrlMapping docs - http://grails.org/doc/latest/guide/theWebLayer.html#urlmappings
url mapping:
"/api/element/$version/$master" {
controller = "element"
action = [GET:"show"]
}
This will map the http get to the show method of the controller element.
i.e. the show method:
DRY: The api is probably the same logic as the application. The difference is content negociation.
...
def show = {
def elements = elementService.findByMasterVersion(params.master, params.version)
withFormat {
xml {
render(status:200,text:elements as XML, contentType:"text/xml",encoding:"UTF-8")
}
json { ... }
html { ... }
}
}
Oauth is pretty damn complicated to implement and seems overkill for a lot of situation.
I just finished reading Restful Web Services and Nobody Understands REST or HTTP and am trying to design an API with a RESTful design.
I've noticed a few patterns in API URI design:
http://api.example.com/users
http://example.com/api/users
http://example.com/users
Assume that these designs properly use Accept and Content-type headers for content negotiations between XHTML, JSON, or any format.
Are these URI's a matter of a pure RESTful implementation vs implicit content negotiation?
My thoughts are that by explicitly using API in the URI is so that a client will expect a data format that is not inherently human pleasing hypermedia and can be more easily consumed without explicitly setting an Accept header. In other words, the API is implying that you expect JSON or XML rather than XHTML.
Is this a matter of separating resource representations
logically on the server side?
The only justification I can come up with for why someone would design their URI's with an API subdomain is because, based off my assumption that this is a scaling technique, it should make routing request load easier in a multi-tiered server infrastructure. Maybe situations exist where reverse proxies are stripping the headers? I don't know. Different servers handling different representations?
Maybe a subdomain is used for external consumers only so that the server avoids the overhead from internal usage. Rate limiting?
Am I missing a point?
My proposed design would attempt to follow RESTful practices by setting appropriate headers, using HTTP verbs appropriately and representing resources in a fashion that I feel including 'API' in the URI would be redundant.
Why would someone design a RESTful API with 'API' in the URI?
Or could they? Maybe my problem with not understanding this design is that it doesn't matter as long as it follows some combination of specification which may not lead to a RESTful API implementation but close? There is more than one way to skin a keyboard cat.
HATEOAS related?
Update: While researching this topic I have come to the conclusion that it's important to consider ideas from REST but not to treat it as a religion. Thus, whether or not to have 'api' in the URI is more of a design decision than a steadfast rule. If you plan to expose your website's API publicly it would be a good idea to use an api subdomain to help deal with the application's logic. I hope that someone will contribute their insight for others to learn from.
I would (and have) done it to separate it from the 'website' infrastructure because it's probably going to have a higher load and require more infrastructure - it's a lot easier to do millions of API calls a day than get that in page views because you have the full load of n sites/companies and their efforts and traction, collectively and even in some cases individually they're going to attract more traffic than you yourself.
This is my understanding and point of view about your question :
Are these URI's a matter of a pure RESTful implementation vs implicit
content negotiation?
No, they are not part of any official documentation (that I know of), and are usually at the developper/team standards discretion. For example, Zend Framework uses some utility classes to detect XHR requests and how responses should be returned. Granted, ZF is not pure RESTful design (or most PHP application as a matter of fact), but it is still possible to write such designs even in PHP.
I have often seen api being used in urls when the returned data expected is indeed not meant to be used as is for display to the end user. However it is usually a design decision and not necessarily an implied standard.
Is this a matter of separating resource representations logically on
the server side?
More or less. For example, when performing a PUT request, for example, the interface does not necessarily need to be entirely refreshed, and often a simple response message is good enough. While this response message is part of the view, it is not the view. So, for example, http://domay.com/users/ would return the interface to manage users (or whatever), http://domain.com/users/api would perform operations and return interface updates (without a page reload).
Am I missing a point?
Weell, no. Since it is a design decision to use or not api in the URL, you're not missing anything here. With the proper headers,
http://domain.com/users/api/get
http://domain.com/users/get
http://domain.com/users/
can all be valid RESTful requests.
Why would someone design a RESTful API with 'API' in the URI?
Simply put, to have an URL naming convention. So that, when looking at a request in logs, documentation, etc. One will understand it's purpose.
Also keep in mind, that most frameworks (django, RoR,...) provide URL-based routing out of the box. You probably need different views for API vs. HTML responses to manage things like authentication, trotting, limits-check and other specific stuff differently.
Putting in place an additional HTTP-Header based routing system to allow, as you say, implicit content negotiation is often not worth the effort.
User-visible webpage URLs are subject to the whims of webmasters, designers, corporate organization, marketing, fashion, technology, etc.
An API, on the other hand, is supposed to remain stable. By using a subdomain you isolate your API from the rest of the website and the changes it is likely to undergo in time.
I see APIs such as PayPal, etc. offering to call their services using NVP or SOAP/WSDL. When using a .NET environment (3.5) using traditional web services (no WCF) which is better and why? I know WSDL lets you drop in the API URL and it generates the wrappers for you. So then why do companies even offer NVP?
There seems to be never-ending confusion in this industry about the different types of web services.
SOAP is a messaging protocol. It has as much in common with REST as an apple has with a lawn tractor. Some of the things you want in a messaging protocol are:
Headers and other non-content "attributes."
Addressing - routing of a message to different servers/recipients based on the headers;
Guaranteed delivery via queuing and other methods;
Encryption, signing, and other security features;
Transactions and orchestrations;
Accurate representation of complex structured data in a single message;
...and so on. This is not an exhaustive list. What WSDL adds to SOAP, primarily, is:
Discoverability via a contract, a form of machine-readable "documentation" that tells consumers exactly what is required in order to send a message and allows proxies to be auto-generated;
Strict, automated schema validation of messages, the same way XSD works for XML.
REST is not a messaging protocol. REST is a system of resources and actions. It is a solid choice for many architectures for several important reasons as outlined by other answers. It also has little to no relevance to "NVP" services like PayPal and flickr.
PayPal's NVP API is not REST. It is an alternative, RPC-like messaging protocol over HTTP POST for clients that don't support or have difficulty supporting SOAP. This isn't my opinion, it's a statement of fact. One of the fields in the NVP is actually METHOD. This is clearly RPC verbiage. Take a look at their API for UpdateRecurringPaymentsProfile and try to tell me that this makes a lick of sense to describe as a "resource". It's not a resource, it's an operation.
In the case of PayPal specifically, the "NVP" (HTTP POST) API is inferior to the SOAP API in almost every way. It is there for consumers who can't use SOAP. If you can use it, you definitely should.
And I'm not necessarily bashing PayPal for this, either. I know a lot of folks have bashed them for not putting together a "proper" RESTful API but that is not what I am getting at. Not every service in the world can be accurately described with REST. PayPal isn't really a resource-based system, it's a transactional system, so I can forgive their architects and developers for not having a perfectly elegant REST architecture. It's debatable perhaps, but it's not black-and-white. It's fine; I'll just use the SOAP system if I need to.
Compare this to, say, the Twitter API. This is a true REST service. Every "operation" you can perform on this API is accurately described as either the retrieval or submission of a particular kind of resource. A resource is a tweet, a status, a user. In this case it literally makes no sense to use a complex SOAP API because you're not really sending messages, you're not performing transactions, you're just asking for specific things, and these things can be described with a single URL. The only difference is that instead of getting an HTML web page back, you're getting some XML or JSON data; the way you request it is exactly the same.
A REST Web Service usually (always?) uses HTTP GET for the retrieval of some resource. And Twitter does exactly this. GET still uses "Name-Value Pairs" - that's the query string, ?q=twitterapi&show_user=true. Those bits after the ? are name-value pairs. And here's a great example of why you would want to use REST over SOAP; you can hook this up to an RSS feed and get streaming updates. I can turn it into a Live Bookmark in Firefox. Or I can download it in JSON format and bind it to something like a jqGrid. The interesting thing is not that the request uses "Name-Value Pairs"; the interesting thing is that it's a simple URL and can be consumed by anything that knows how to request a web page.
So to try and summarize all of what I've said, think of it this way:
Use a REST API (if available) when you want to expose data, or consume or publish it, as a permanent resource.
Use a SOAP API when the system is transactional in nature and/or when you need the advanced features that a complex messaging protocol can offer, such as RM and addressing.
Use an RPC API (which includes just about any API that's modeled entirely around HTTP POST) when there is no SOAP API or when you are unable to use the SOAP API.
Hope that clears up some of the confusion.
I assume that by Name Value Pairs, you mean REST services.
The benefits to REST are primarily ease of development, simplicity and elegance, and lower overhead (which is very important if you are sending and receiving a lot of small messages).
Here are some of the advantages of REST:
REST is more lightweight
Human readable results
Everything is a URI addressable resource
REST services are more easily cached
REST is easier to build (no toolkits are required)
REST is easier to call (HTTP - GET, POST, PUT, DELETE)
NVP is HTTP POST
name=fred
amount=100
code=403
etc
This is the default format from any HTML browser so it's simple to implement for sending data to a web service
I don't think it's a good format for receiving data from web service? JSON or XML would be more suitable
No everyone uses VisualStudio, or has access to automatic wrapper generators, or wants to use such a beast
Many web mashups are coded in Javascript, so using HTTP POST to send data is the simplest way. The return result is a standard HTML response code (200, 403, 500, etc) and/or some JSON
Many service providers offer multiple API's to cater for all customers