I'm new to REST and I've observed that in some RESTful services they use different resource URI for update/get/delete and Create. Such as
I'm little bit confused about this URI naming convention. What should we use plural or singular for resource creation? What should be the criteria while deciding that?
The premise of using /resources is that it is representing "all" resources. If you do a GET /resources, you will likely return the entire collection. By POSTing to /resources, you are adding to the collection.
However, the individual resources are available at /resource. If you do a GET /resource, you will likely error, as this request doesn't make any sense, whereas /resource/123 makes perfect sense.
Using /resource instead of /resources is similar to how you would do this if you were working with, say, a file system and a collection of files and /resource is the "directory" with the individual 123, 456 files in it.
Neither way is right or wrong, go with what you like best.
For me is better to have a schema that you can map directly to code (easy to automate), mainly because code is what is going to be at both ends.
GET /orders <---> orders
POST /orders <---> orders.push(data)
GET /orders/1 <---> orders[1]
PUT /orders/1 <---> orders[1] = data
GET /orders/1/lines <---> orders[1].lines
POST /orders/1/lines <---> orders[1].lines.push(data)
I don't see the point in doing this either and I think it is not the best URI design. As a user of a RESTful service I'd expect the list resource to have the same name no matter whether I access the list or specific resource 'in' the list. You should use the same identifiers no matter whether you want use the list resource or a specific resource.
Plural
orders/ gets an index list of orders.For example:
GET /resources - returns a list of resource items
POST /resources - creates one or many resource items
PUT /resources - updates one or many resource items
PATCH /resources - partially updates one or many resource items
DELETE /resources - deletes all resource items
And for single resource items:
GET /resources/:id - returns a specific resource item based on :id parameter
POST /resources/:id - creates one resource item with specified id (requires validation)
PUT /resources/:id - updates a specific resource item
PATCH /resources/:id - partially updates a specific resource item
DELETE /resources/:id - deletes a specific resource item
To the advocates of singular, think of it this way: Would you ask a someone for an order and expect one thing, or a list of things? So why would you expect a service to return a list of things when you type /order?
Convenience Things can have irregular plural names. Sometimes they don't have one. But Singular names are always there.
e.g. CustomerAddress over CustomerAddresses
Consider this related resource.
This /order/12/orderdetail/12 is more readable and logical than /orders/12/orderdetails/4.
A resource represents an entity like a database table. It should have a logical singular name. Here's the answer over table names.
Classes are always singular. ORM tools generate tables with the same names as class names. As more and more tools are being used, singular names are becoming a standard.
Read more about A REST API Developer's Dilemma
In the case of trousers and sunglasses, they don't seem to have a singular counterpart. They are commonly known and they appear to be singular by use. Like a pair of shoes. Think about naming the class file Shoe or Shoes. Here these names must be considered as a singular entity by their use. You don't see anyone buying a single shoe to have the URL as
/shoe/23
We have to see Shoes as a singular entity.
Reference: Top 6 REST Naming Best Practices
Whereas the most prevalent practice are RESTful apis where plurals are used e.g. /api/resources/123 , there is one special case where I find use of a singular name more appropriate/expressive than plural names. It is the case of one-to-one relationships. Specifically if the target item is a value object(in Domain-driven-design paradigm).
Let us assume every resource has a one-to-one accessLog which could be modeled as a value object i.e not an entity therefore no ID. It could be expressed as /api/resources/123/accessLog. The usual verbs (POST, PUT, DELETE, GET) would appropriately express the intent and also the fact that the relationship is indeed one-to-one.
From the API consumer's perspective, the endpoints should be predictable so
Ideally...
GET /resources should return a list of resources. GET /resource should return a 400 level status code.GET /resources/id/{resourceId} should return a collection with one resource.GET /resource/id/{resourceId} should return a resource object.POST /resources should batch create resources.POST /resource should create a resource.PUT /resource should update a resource object.PATCH /resource should update a resource by posting only the changed attributes.PATCH /resources should batch update resources posting only the changed attributes.DELETE /resources should delete all resources; just kidding: 400 status codeDELETE /resource/id/{resourceId}This approach is the most flexible and feature rich, but also the most time consuming to develop. So, if you're in a hurry (which is always the case with software development) just name your endpoint resource or the plural form resources. I prefer the singular form because it gives you the option to introspect and evaluate programmatically since not all plural forms end in 's'.
Having said all that, for whatever reason the most commonly used practice developer's have chosen is to use the plural form. This is ultimately the route I have chosen and if you look at popular apis like github and twitter, this is what they do.
Some criteria for deciding could be:
So it's up to you. Just whatever you do be consistent.
I am surprised to see that so many people would jump on the plural noun bandwagon. When implementing singular to plural conversions, are you taking care of irregular plural nouns? Do you enjoy pain?
See http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/irrplu.htm
There are many types of irregular plural, but these are the most common:
Noun type Forming the plural Example
Ends with -fe Change f to v then Add -s
knife knives
life lives
wife wives
Ends with -f Change f to v then Add -es
half halves
wolf wolves
loaf loaves
Ends with -o Add -es
potato potatoes
tomato tomatoes
volcano volcanoes
Ends with -us Change -us to -i
cactus cacti
nucleus nuclei
focus foci
Ends with -is Change -is to -es
analysis analyses
crisis crises
thesis theses
Ends with -on Change -on to -a
phenomenon phenomena
criterion criteria
ALL KINDS Change the vowel or Change the word or Add a different ending
man men
foot feet
child children
person people
tooth teeth
mouse mice
Unchanging Singular and plural are the same
sheep deer fish (sometimes)
An id in a route should be viewed the same as an index to a list, and naming should proceed accordingly.
numbers = [1, 2, 3]
numbers GET /numbers
numbers[1] GET /numbers/1
numbers.push(4) POST /numbers
numbers[1] = 23 UPDATE /numbers/1
But some resources don't use ids in their routes because there's either only one, or a user never has access to more than one, so those aren't lists:
GET /dashboard
DELETE /session
POST /login
GET /users/{:id}/profile
UPDATE /users/{:id}/profile
My two cents: methods who spend their time changing from plural to singular or viceversa are a waste of CPU cycles. I may be old-school, but in my time like things were called the same. How do I look up methods concerning people? No regular expresion will cover both person and people without undesirable side effects.
English plurals can be very arbitrary and they encumber the code needlessly. Stick to one naming convention. Computer languages were supposed to be about mathematical clarity, not about mimicking natural language.
I prefer using singular form for both simplicity and consistency.
For example, considering the following url:
/customer/1
I will treat customer as customer collection, but for simplicity, the collection part is removed.
Another example:
/equipment/1
In this case, equipments is not the correct plural form. So treating it as a equipment collection and removing collection for simplicity makes it consistent with the customer case.
See Google's API Design Guide: Resource Names for another take on naming resources.
The guide requires collections to be named with plurals.
|--------------------------+---------------+-------------------+---------------+--------------|
| API Service Name | Collection ID | Resource ID | Collection ID | Resource ID |
|--------------------------+---------------+-------------------+---------------+--------------|
| //mail.googleapis.com | /users | /[email protected] | /settings | /customFrom |
| //storage.googleapis.com | /buckets | /bucket-id | /objects | /object-id |
|--------------------------+---------------+-------------------+---------------+--------------|
It's worthwhile reading if you're thinking about this subject.
With naming conventions, it's usually safe to say "just pick one and stick to it", which makes sense.
However, after having to explain REST to lots of people, representing endpoints as paths on a file system is the most expressive way of doing it.
It is stateless (files either exist or don't exist), hierarchical, simple, and familiar - you already knows how to access static files, whether locally or via http.
And within that context, linguistic rules can only get you as far as the following:
A directory can contain multiple files and/or sub-directories, and therefore its name should be in plural form.
And I like that.
Although, on the other hand - it's your directory, you can name it "a-resource-or-multiple-resources" if that's what you want. That's not really the important thing.
What's important is that if you put a file named "123" under a directory named "resourceS" (resulting in /resourceS/123), you cannot then expect it to be accessible via /resource/123.
Don't try to make it smarter than it has to be - changing from plural to singluar depending on the count of resources you're currently accessing may be aesthetically pleasing to some, but it's not effective and it doesn't make sense in a hierarchical system.
Note: Technically, you can make "symbolic links", so that /resources/123 can also be accessed via /resource/123, but the former still has to exist!
Use Singular and take advantage of the English convention seen in e.g. "Business Directory".
Lots of things read this way: "Book Case", "Dog Pack", "Art Gallery", "Film Festival", "Car Lot", etc.
This conveniently matches the url path left to right. Item type on the left. Set type on the right.
Does GET /users really ever fetch a set of users? Not usually. It fetches a set of stubs containing a key and perhaps a username. So it's not really /users anyway. It's an index of users, or a "user index" if you will. Why not call it that? It's a /user/index. Since we've named the set type, we can have multiple types showing different projections of a user without resorting to query parameters e.g. user/phone-list or /user/mailing-list.
And what about User 300? It's still /user/300.
GET /user/index
GET /user/{id}
POST /user
PUT /user/{id}
DELETE /user/{id}
In closing, HTTP can only ever have a single response to a single request. A path is always referring to a singular something.
I don't like to see the {id} part of the URLs overlap with sub-resources, as an id could theoretically be anything and there would be ambiguity. It is mixing different concepts (identifiers and sub-resource names).
Similar issues are often seen in enum constants or folder structures, where different concepts are mixed (for example, when you have folders Tigers, Lions and Cheetahs, and then also a folder called Animals at the same level -- this makes no sense as one is a subset of the other).
In general I think the last named part of an endpoint should be singular if it deals with a single entity at a time, and plural if it deals with a list of entities.
So endpoints that deal with a single user:
GET /user -> Not allowed, 400
GET /user/{id} -> Returns user with given id
POST /user -> Creates a new user
PUT /user/{id} -> Updates user with given id
DELETE /user/{id} -> Deletes user with given id
Then there is separate resource for doing queries on users, which generally return a list:
GET /users -> Lists all users, optionally filtered by way of parameters
GET /users/new?since=x -> Gets all users that are new since a specific time
GET /users/top?max=x -> Gets top X active users
And here some examples of a sub-resource that deals with a specific user:
GET /user/{id}/friends -> Returns a list of friends of given user
Make a friend (many to many link):
PUT /user/{id}/friend/{id} -> Befriends two users
DELETE /user/{id}/friend/{id} -> Unfriends two users
GET /user/{id}/friend/{id} -> Gets status of friendship between two users
There is never any ambiguity, and the plural or singular naming of the resource is a hint to the user what they can expect (list or object). There are no restrictions on ids, theoretically making it possible to have a user with the id new without overlapping with a (potential future) sub-resource name.
Both representations are useful. I had used singular for convenience for quite some time, inflection can be difficult. My experience in developing strictly singular REST APIs, the developers consuming the endpoint lack certainty in what the shape of the result may be. I now prefer to use the term that best describes the shape of the response.
If all of your resources are top level, then you can get away with singular representations. Avoiding inflection is a big win.
If you are doing any sort of deep linking to represent queries on relations, then developers writing against your API can be aided by having a stricter convention.
My convention is that each level of depth in a URI is describing an interaction with the parent resource, and the full URI should implicitly describe what is being retrieved.
Suppose we have the following model.
interface User {
<string>id;
<Friend[]>friends;
<Manager>user;
}
interface Friend {
<string>id;
<User>user;
...<<friendship specific props>>
}
If I needed to provide a resource that allows a client to get the manager of a particular friend of a particular user, it might look something like:
GET /users/{id}/friends/{friendId}/manager
The following are some more examples:
GET /users - list the user resources in the global users collectionPOST /users - create a new user in the global users collectionGET /users/{id} - retrieve a specific user from the global users collectionGET /users/{id}/manager - get the manager of a specific userGET /users/{id}/friends - get the list of friends of a userGET /users/{id}/friends/{friendId} - get a specific friend of a userLINK /users/{id}/friends - add a friend association to this userUNLINK /users/{id}/friends - remove a friend association from this userNotice how each level maps to a parent that can be acted upon. Using different parents for the same object is counterintuitive. Retrieving a resource at GET /resource/123 leaves no indication that creating a new resource should be done at POST /resources
I know most people are between deciding whether to use plural or singular. The issue that has not been addressed here is that the client will need to know which one you are using, and they are always likely to make a mistake. This is where my suggestion comes from.
How about both? And by that, I mean use singular for your whole API and then create routes to forward requests made in the plural form to the singular form. For example:
GET /resources = GET /resource
GET /resources/1 = GET /resource/1
POST /resources/1 = POST /resource/1
...
You get the picture. No one is wrong, minimal effort, and the client will always get it right.
To me plurals manipulate the collection, whereas singulars manipulate the item inside that collection.
Collection allows the methods GET / POST / DELETE
Item allows the methods GET / PUT / DELETE
For example
POST on /students will add a new student in the school.
DELETE on /students will remove all the students in the school.
DELETE on /student/123 will remove student 123 from the school.
It might feel like unimportant but some engineers sometimes forget the id. If the route was always plural and performed a DELETE, you might accidentally wipe your data. Whereas missing the id on the singular will return a 404 route not found.
To further expand the example if the API was supposed to expose multiple schools, then something like
DELETE on /school/abc/students will remove all the students in the school abc.
Choosing the right word sometimes is a challenge on its own, but I like to maintain plurality for the collection. E.g. cart_items or cart/items feels right. In contrast deleting cart, deletes the cart object it self and not the items within the cart ;).
/pants, /eye-glasses - are those the singular or the plural path?
/radii - do you know off the top of your head if the singular path for that is /radius or /radix?
/index - do you know off the top of your head if plural path for that is /indexes or /indeces or /indices?
Any time you are using plurals in interfaces and code, ask yourself, how does your convention handle words like the above?
Conventions should ideally scale without irregularity. English plurals do not do this, because
This has downsides. The most prominent ones off the top of my head:
/foo/{{id}}, what's the path to get all foo?" into a natural language problem instead of a "just drop the last path part" problem.Meanwhile, some human languages don't even have different singular and plural forms for nouns. They manage just fine. So can your API.
I prefer to use both plural (/resources) and singular (/resource/{id}) because I think that it more clearly separates the logic between working on the collection of resources and working on a single resource.
As an important side-effect of this, it can also help to prevent somebody using the API wrongly. For example, consider the case where a user wrongly tries to get a resource by specifying the Id as a parameter like this:
GET /resources?Id=123
In this case, where we use the plural version, the server will most likely ignore the Id parameter and return the list of all resources. If the user is not careful, he will think that the call was successful and use the first resource in the list.
On the other hand, when using the singular form:
GET /resource?Id=123
the server will most likely return an error because the Id is not specified in the right way, and the user will have to realize that something is wrong.
