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title |
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Rest API Design |
History
REST stands for Representational State Transfer protocol. Roy Fielding defined REST in his Phd dissertation in year 2000.
What is it?
REST was developed to provide a uniform interface for
- Identifying resources
- Manipulation of resources
- Self-descriptive messages
- Using Hypermedia as the Engine of Application State (HATEOS)
Best Practices
-
Basics
Method | http://api.co/v2/cars | http://api.co/v2/cars/1234 |
---|---|---|
GET | List all the cars | Retrieve an individual car |
POST | Create a new car | Error |
PUT | Replace cars collections with new one | Replace the car with id 1234 |
DELETE | Delete all cars | Delete car with id 1234 |
Note while PUT operations either client or server can generate id's
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Nouns are good, Verbs are bad
- Use nouns to refer resources like
cars
,fruits
etc. - Use verbs for action declarations
convertMilesToKms
,getNutritionalValues
- Use nouns to refer resources like
-
Singular or Plural?
Use correct grammar for declaration
Avoid
/person/145
Prefer
/people/154
Assumed to return 154th person from list of people -
Use casing
Use anyone of the below patterns and be consistent!
Case Styles Example UpperCamelCase http://api.fintech.cp/DailyTransactions/Today
lowerCamelCase http://api.fintech.cp/dailyTransactions/today
snake_case http://api.fintech.cp/daily_transactions/today
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Relationships and Resources
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Resources can have
one-to-one
,one-to-many
, andmany-to-many
relationships etc. Mapping them correctly is crucial. -
One-to-One Mapping
For example,
Countries/1/capital
suggests a one-to-one relationship between a country and a capital city. This means a country can only have one capital. This type of relationship means that one row relates only to one row in another table (one country, one capital in two different tables). This type of relationship is not common and is often used to break up the amount of data in one row of a table. -
One-to-Many Mapping
For example,
Tickets/145/messages/4
suggests one-to-many relationship betweentickets
andmessages
. Meaning1
ticket hasN
messages. Message isn't standalone resource. You can't have/messages/4
. -
Many to Many Mapping
For example,
/usergroups/345/users/56
suggests select 345th user group and get user with id 56. However, one user might be in multipleusergroups
i.e./usergroups/209/users/56
is also valid. In such case so for seperating the dependant resourceusers
into a seperate endpoint like/users/56
and provide resource linking in/usergroups/209/users/56
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API Parameters
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PATH : required to access the resource E.g.
/cars
,/fruits
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Query Parameters : optional filter the list E.g.
/cars?type=SUV&year=2010
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Body : Resource specific logic. Advance search query. Sometimes it might have both Query and body.
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Header : Should contain global or platform wide data. E.g. API key parameters, encrypted keys for auth, device type information e.g. mobile or desktop or endpoint, device data type e.g. xml or json. Use header to communicate these parameters
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HTTP Status Codes
Use correct status codes
Codes | Meaning |
---|---|
1xx | Request received and understood. |
2xx | Action requested by client was received, understood and requested. |
3xx | Client must take additional action to complete the request. Most of these status codes are used in URL Redirection. |
4xx | Intended for situations where it seems the error was caused by the client. |
5xx | The server failed to fulfil a request. |
Little more on 2xx!
-
201 Resource Created. POST
/cars
should return HTTP 201 created withlocation
header stating how to access the resource E.g.location
:api.com/cars/124
in header -
202 - Accepted
Use this if the task is huge to run. Tell the client, it has accepted the request and will/is process/processing No payload is returned
-
204 - No content
Used when deleted
DELETE cars/124
Returns no content. But can also return200 OK
if API intends to send the deleted resource for further processing.
The dangerous 5xx resources!
- 500 Internal Server Error
- 501 Not implemented. Server lacks the ability to fulfil the request
- 504 Gateway Timeout. Server didn't receive timely response
Less known 4xx suggests that you are passing wrong parameter. Can also pass information that is wrong. E.g.
DELETE /cars/MH09234
returns 4xx
or message
Expecting int car id /car/id got string car/MH09234
Further reading
How to Design Great APIs - Parse Developer Day 2013
The never-ending REST API design debate by Guillaume Laforge