Apparently, REST is just a set of conventions about how to use HTTP. I wonder which advantage these conventions provide. Does anyone know?开发者_C百科

I don't think you will get a good answer to this, partly because nobody really agrees on what REST is. The wikipedia page is heavy on buzzwords and light on explanation. The discussion page is worth a skim just to see how much people disagree on this. As far as I can tell however, REST means this:

Instead of having randomly named setter and getter URLs and using GET for all the getters and POST for all the setters, we try to have the URLs identify resources, and then use the HTTP actions GET, POST, PUT and DELETE to do stuff to them. So instead of

GET /get_article?id=1
POST /delete_article   id=1

You would do

GET /articles/1/
DELETE /articles/1/

And then POST and PUT correspond to "create" and "update" operations (but nobody agrees which way round).

I think the caching arguments are wrong, because query strings are generally cached, and besides you don't really need to use them. For example django makes something like this very easy, and I wouldn't say it was REST:

GET /get_article/1/
POST /delete_article/     id=1

Or even just include the verb in the URL:

GET /read/article/1/
POST /delete/article/1/
POST /update/article/1/
POST /create/article/

In that case GET means something without side-effects, and POST means something that changes data on the server. I think this is perhaps a bit clearer and easier, especially as you can avoid the whole PUT-vs-POST thing. Plus you can add more verbs if you want to, so you aren't artificially bound to what HTTP offers. For example:

POST /hide/article/1/
POST /show/article/1/

(Or whatever, it's hard to think of examples until they happen!)

So in conclusion, there are only two advantages I can see:

Your web API may be cleaner and easier to understand / discover.
When synchronising data with a website, it is probably easier to use REST because you can just say synchronize("/articles/1/") or whatever. This depends heavily on your code.

However I think there are some pretty big disadvantages:

Not all actions easily map to CRUD (create, read/retrieve, update, delete). You may not even be dealing with object type resources.
It's extra effort for dubious benefits.
Confusion as to which way round PUT and POST are. In English they mean similar things ("I'm going to put/post a notice on the wall.").

So in conclusion I would say: unless you really want to go to the extra effort, or if your service maps really well to CRUD operations, save REST for the second version of your API.

I just came across another problem with REST: It's not easy to do more than one thing in one request or specify which parts of a compound object you want to get. This is especially important on mobile where round-trip-time can be significant and connections are unreliable. For example, suppose you are getting posts on a facebook timeline. The "pure" REST way would be something like

GET /timeline_posts     // Returns a list of post IDs.
GET /timeline_posts/1/  // Returns a list of message IDs in the post.
GET /timeline_posts/2/
GET /timeline_posts/3/
GET /message/10/
GET /message/11/
....

Which is kind of ridiculous. Facebook's API is pretty great IMO, so let's see what they do:

By default, most object properties are returned when you make a query. You can choose the fields (or connections) you want returned with the "fields" query parameter. For example, this URL will only return the id, name, and picture of Ben: https://graph.facebook.com/bgolub?fields=id,name,picture

I have no idea how you'd do something like that with REST, and if you did whether it would still count as REST. I would certainly ignore anyone who tries to tell you that you shouldn't do that though (especially if the reason is "because it isn't REST")!

Simply put, REST means using HTTP the way it's meant to be.

Have a look at Roy Fielding's dissertation about REST. I think that every person that is doing web development should read it.

As a note, Roy Fielding is one of the key drivers behind the HTTP protocol, as well.

To name some of the advandages:

Simple.
You can make good use of HTTP cache and proxy server to help you handle high load.
It helps you organize even a very complex application into simple resources.
It makes it easy for new clients to use your application, even if you haven't designed it specifically for them (probably, because they weren't around when you created your app).

Simply put: NONE.

Feel free to downvote, but I still think there are no real benefits over non-REST HTTP. All current answers are invalid. Arguments from the currently most voted answer:

Simple.
You can make good use of HTTP cache and proxy server to help you handle high load.
It helps you organize even a very complex application into simple resources.
It makes it easy for new clients to use your application, even if you haven't designed it specifically for them (probably, because they weren't around when you created your app).

1. Simple

With REST you need additional communication layer for your server-side and client-side scripts => it's actually more complicated than use of non-REST HTTP.

2. Caching

Caching can be controlled by HTTP headers sent by server. REST does not add any features missing in non-REST.

3. Organization

REST does not help you organize things. It forces you to use API supported by server-side library you are using. You can organize your application the same way (or better) when you are using non-REST approach. E.g. see Model-View-Controller or MVC routing.

4. Easy to use/implement

Not true at all. It all depends on how well you organize and document your application. REST will not magically make your application better.

IMHO the biggest advantage that REST enables is that of reducing client/server coupling. It is much easier to evolve a REST interface over time without breaking existing clients.

Discoverability

Each resource has references to other resources, either in hierarchy or links, so it's easy to browse around. This is an advantage to the human developing the client, saving he/she from constantly consulting the docs, and offering suggestions. It also means the server can change resource names unilaterally (as long as the client software doesn't hardcode the URLs).

Compatibility with other tools

You can CURL your way into any part of the API or use the web browser to navigate resources. Makes debugging and testing integration much easier.

Standardized Verb Names

Allows you to specify actions without having to hunt the correct wording. Imagine if OOP getters and setters weren't standardized, and some people used retrieve and define instead. You would have to memorize the correct verb for each individual access point. Knowing there's only a handful of verbs available counters that problem.

Standardized Status

If you GET a resource that doesn't exist, you can be sure to get a 404 error in a RESTful API. Contrast it with a non-RESTful API, which may return {error: "Not found"} wrapped in God knows how many layers. If you need the extra space to write a message to the developer on the other side, you can always use the body of the response.

Example

Imagine two APIs with the same functionality, one following REST and the other not. Now imagine the following clients for those APIs:

RESTful:

GET /products/1052/reviews
POST /products/1052/reviews       "5 stars"
DELETE /products/1052/reviews/10
GET /products/1052/reviews/10

HTTP:

GET /reviews?product_id=1052
POST /post_review?product_id=1052                  "5 stars"
POST /remove_review?product_id=1052&review_id=10
GET /reviews?product_id=1052&review=10

Now think of the following questions:

If the first call of each client worked, how sure can you be the rest will work too?
There was a major update to the API that may or may not have changed those access points. How much of the docs will you have to re-read?
Can you predict the return of the last query?
You have to edit the review posted (before deleting it). Can you do so without checking the docs?

I recommend taking a look at Ryan Tomayko's How I Explained REST to My Wife

Third party edit

Excerpt from the waybackmaschine link:

How about an example. You’re a teacher and want to manage students:

what classes they’re in,
what grades they’re getting,
emergency contacts,
information about the books you teach out of, etc.

If the systems are web-based, then there’s probably a URL for each of the nouns involved here: student, teacher, class, book, room, etc. ... If there were a machine readable representation for each URL, then it would be trivial to latch new tools onto the system because all of that information would be consumable in a standard way. ... you could build a country-wide system that was able to talk to each of the individual school systems to collect testing scores.

Each of the systems would get information from each other using a simple HTTP GET. If one system needs to add something to another system, it would use an HTTP POST. If a system wants to update something in another system, it uses an HTTP PUT. The only thing left to figure out is what the data should look like.

I would suggest everybody, who is looking for an answer to this question, go through this "slideshow".

I couldn't understand what REST is and why it is so cool, its pros and cons, differences from SOAP - but this slideshow was so brilliant and easy to understand, so it is much more clear to me now, than before.

Caching.

There are other more in depth benefits of REST which revolve around evolve-ability via loose coupling and hypertext, but caching mechanisms are the main reason you should care about RESTful HTTP.

It's written down in the Fielding dissertation. But if you don't want to read a lot:

increased scalability (due to stateless, cache and layered system constraints)
decoupled client and server (due to stateless and uniform interface constraints)
- reusable clients (client can use general REST browsers and RDF semantics to decide which link to follow and how to display the results)
- non breaking clients (clients break only by application specific semantics changes, because they use the semantics instead of some API specific knowledge)

Give every “resource” an ID
Link things together
Use standard methods
Resources with multiple representations
Communicate statelessly

It is possible to do everything just with POST and GET? Yes, is it the best approach? No, why? because we have standards methods. If you think again, it would be possible to do everything using just GET.. so why should we even bother do use POST? Because of the standards!

For example, today thinking about a MVC model, you can limit your application to respond just to specific kinds of verbs like POST, GET, PUT and DELETE. Even if under the hood everything is emulated to POST and GET, don't make sense to have different verbs for different actions?

Discovery is far easier in REST. We have WADL documents (similar to WSDL in traditional webservices) that will help you to advertise your service to the world. You can use UDDI discoveries as well. With traditional HTTP POST and GET people may not know your message request and response schemas to call you.

One advantage is that, we can non-sequentially process XML documents and unmarshal XML data from different sources like InputStream object, a URL, a DOM node...

@Timmmm, about your edit :

GET /timeline_posts     // could return the N first posts, with links to fetch the next/previous N posts

This would dramatically reduce the number of calls

And nothing prevents you from designing a server that accepts HTTP parameters to denote the field values your clients may want...

But this is a detail.

Much more important is the fact that you did not mention huge advantages of the REST architectural style (much better scalability, due to server statelessness; much better availability, due to server statelessness also; much better use of the standard services, such as caching for instance, when using a REST architectural style; much lower coupling between client and server, due to the use of a uniform interface; etc. etc.)

As for your remark

"Not all actions easily map to CRUD (create, read/retrieve, update, delete)."

: an RDBMS uses a CRUD approach, too (SELECT/INSERT/DELETE/UPDATE), and there is always a way to represent and act upon a data model.

Regarding your sentence

"You may not even be dealing with object type resources"

: a RESTful design is, by essence, a simple design - but this does NOT mean that designing it is simple. Do you see the difference ? You'll have to think a lot about the concepts your application will represent and handle, what must be done by it, if you prefer, in order to represent this by means of resources. But if you do so, you will end up with a more simple and efficient design.

Query-strings can be ignored by search engines.