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I am supposed to make web services for an app and thought I could do a nice job practicing the good practice. As I found out it's using REST. But there is one thing that makes very little sense in it.

Why use URI to pass any variable?

What we did in our last project is use POST only and pass whatever as raw POST data (which was JSON). That's not very RESTful. But it has some advantages. It was quite simple on the client side - I had a general function that takes URI and data as arguments and then it wraps it up and sends it.

Now, if I used proper REST, I would have to pass some data as part of the URI (user ID, for instance). All the other data (username, email and etc.) would have to go as raw data, like we did, I guess. That means I would have to separate user ID and the other data at some point. That's not so bad but still - why?

EDIT Here is a more detailed example:

Let's say you want to access (GET) and update (POST) user data. You may have a service accessible under /user but what RESTful service would do is accept user's ID as part of the URI (/user/1234). All the other data (name, email and etc) would go to request content (probably as JSON).

What I pose is that it seems useless to make put user id in the URI. If you wanted to update user data - you would send additional data as content anyway. If you wanted to access it - you could use same generic method to request web service.

I know GET gets cached by a browser but I believe you have to cache it manually anyway if you use AJAX (web) or any HTTP client library (other platforms).

From point of scalability - you can always add more services.

Pijusn
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    I believe my [answer to a different question](http://stackoverflow.com/questions/4573305/rest-api-why-use-put-delete-post-get/4573426#4573426) is relevant. – zzzzBov Aug 26 '12 at 06:35
  • Good answer. Actually, the very first sentence explains quite a lot (the fact that REST is not about simplicity). – Pijusn Aug 26 '12 at 06:45

2 Answers2

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You use the URI to identify the resource (user/document/webpage) you want to work with, and pass the related data inside the request.

It has the advantage that web infrastructure components can find out the location of the resource without having any idea how your content is represented. For example, you can use standard caches and load balancers, all they need to know is the URL and headers (which are always represented the same way) Whether you use JSON, protobuf or WAV audio to communicate with your resource is irrelevant.

This will for example let you keep different resources in totally different places, if you send it all as content you won't have the advantage of being able to place the resources in totally different locations, as for example http://cloud.google.com/resource1 and http://cloud.amazon.com/resource2.

All this will allow you to scale massively, which you won't be able to do if you put it all on http://my.url.com/rest and pass all resource info as content.

Re: Your edit

Passing the user id in the URL is the only way to identify the individual resource (user). Remember, it's the user that's the resource, not the "user store".

For example, a cache that caches http://my.url/user won't be much good, since it would return the same cached page for every user. If the cache can work with http://my.url/user/4711, it can cache every user separately. In the same way, a load balancer could know that users 1-5000 are handled by one machine, 5001-10000 by another etc. and make intelligent decisions based on the URL only.

Joachim Isaksson
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  • well, that is pretty clear. That was what we did previously as well, have multiple services which were located (at least it seemed so from point of URI) in different locations. I am more interested in cases where you access user by having URI which combines both, service name (resource you wanna work with) and some of it's data (like ID). I will edit my post with more detailed example soon. – Pijusn Aug 26 '12 at 06:24
  • Your reply makes sense. Didn't really think about balancers and etc. – Pijusn Aug 26 '12 at 10:39
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Imagine a RESTful web service as a database. To get or modify specific object you need to identify it by providing its primary key. You identify a user by his ID, not his Name+Nickname+e-mail+mother's maiden name. The information that identifies an object or selects a set of objects goes to the URL. The information that modifies objects should be POSTed to the corresponding URL.

Ark-kun
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