restful It is recommended to see the great God's blog

tslint Comment mark

ts Use the following comment in the file to temporarily ignore the error of the rule , Reference here

• / tslint:disable /—— Ignore the error prompt in all the following code on this line
• / tslint:enable /—— At present ts File re enable tslint
• // tslint:disable-line—— Ignore the error prompt in the current line of code
• // tslint:disable-next-line—— Ignore the error prompt in the next line of code

RESTful

A style of software architecture 、 Design style , and No standard , It just provides a set of design principles and constraints . It is mainly used for the software of interaction between client and server . Software designed based on this style can be more concise , More layers , It is easier to implement caching and other mechanisms .

Principle conditions ：

Web The most important part of an application is REST The principle is , The interaction between client and server is stateless between requests . Every request from the client to the server must contain the information necessary to understand the request . If the server restarts at any point in time between requests , The client will not be notified . Besides , Stateless requests can be answered by any available server , This is very suitable for Cloud computing Or something like that . Clients can cache data to improve performance .

On the server side , Application state and function can be divided into various resources . Resources are an interesting conceptual entity , It's open to clients . Examples of resources are ： Application object 、 Database records 、 Algorithm, etc. . Every resource uses URI (Universal Resource Identifier) Get a unique address . All resources share a unified interface , To transfer state between client and server . It's standard HTTP Method , such as GET、PUT、POST and DELETE.Hypermedia Is the status of the application engine , Resources are represented by Hyperlinks interconnection .

PRC： Remote procedure call
RFC：request for comments Request comments

The purpose of my article , I want to be consistent with the principle of architecture , Understand and evaluate the architecture design of web-based applications , Get a powerful 、 Good performance 、 Architecture suitable for communication .REST A set of architectural constraints and principles .

REST It doesn't create new technology in itself 、 Components or services , And hidden in RESTful The idea behind it is to use Web The existing characteristics and capabilities of , Better use of existing Web Some criteria and constraints in the standard . although REST Self acceptance Web Technology has a profound impact , But in theory REST The architectural style is not tied to HTTP On , Just for now HTTP Is the only one with REST Relevant examples . So what we're describing here REST through HTTP Realized REST.

From the definition of resources 、 obtain 、 describe 、 relation 、 State change and so on , List and explain some key concepts :

Resources and URI

** Anything , As long as there is a need to be quoted , It's a resource . Resources can be entities ( For example, cell phone numbers ), It can also be just an abstract concept ( For example, value ) **

URI:uniform resource identifier

URI The design of the system should follow the principle of addressability , Self descriptive , Need to give people an intuitive connection in form .

Unified resource interface

RESTFul Architecture should follow the principle of unified interface , The unified interface contains a limited set of predefined operations , No matter what kind of resources , All access resources through the same interface .

GET

• Safe and idempotent
• Get representation
• Get representation on change （ cache ）
• 200（OK） - Indicates that... Has been issued in the response
• 204（ There is no content ） - If the resource is empty, it means
• 301（Moved Permanently） - Resources URI Has been updated
• 303（See Other） - other （ Such as , Load balancing ）
• 304（not modified）- The resource has not changed （ cache ）
• 400 （bad request）- A bad request （ Such as , Parameter error ）
• 404 （not found）- Resource does not exist
• 406 （not acceptable）- The server does not support the required representation
• 500 （internal server error）- General error response
• 503 （Service Unavailable）- The server is currently unable to process the request

POST

• Not safe and idempotent
• Using server managed （ Automatically generate ） Instance number of create resource
• Create sub resources
• Partial update resources
• If it's not modified , But update the resources （ Optimism lock ）
• 200（OK）- If an existing resource has been changed
• 201（created）- If a new resource is created
• 202（accepted）- Processing request accepted but not completed （ Asynchronous processing ）
• 301（Moved Permanently）- Resources URI Be updated
• 303（See Other）- other （ Such as , Load balancing ）
• 400（bad request）- A bad request
• 404 （not found）- Resource does not exist
• 406 （not acceptable）- The server does not support the required representation
• 409 （conflict）- Generic conflict
• 412 （Precondition Failed）- Precondition failed （ Such as the conflict when executing condition update ）
• 415 （unsupported media type）- The received expression is not supported
• 500 （internal server error）- General error response
• 503 （Service Unavailable）- The service is currently unable to process the request

PUT

• Unsafe but idempotent
• Create a resource with the instance number managed by the client
• Update resources by replacing
• If not modified , Update resources （ Optimism lock ）
• 200 （OK）- If an existing resource is changed
• 201 （created）- If a new resource is created
• 301（Moved Permanently）- Resources URI Has been changed
• 303 （See Other）- other （ Such as , Load balancing ）
• 400 （bad request）- A bad request
• 404 （not found）- Resource does not exist
• 406 （not acceptable）- The server does not support the required representation
• 409 （conflict）- Generic conflict
• 412 （Precondition Failed）- Precondition failed （ Such as the conflict when executing condition update ）
• 415 （unsupported media type）- The received expression is not supported
• 500 （internal server error）- General error response
• 503 （Service Unavailable）- The service is currently unable to process the request

DELETE

• Unsafe but idempotent
• Delete resources
• 200 （OK）- The resource has been deleted
• 301 （Moved Permanently）- Resources URI Has been changed
• 303 （See Other）- other , Such as load balancing
• 400 （bad request）- A bad request
• 404 （not found）- Resource does not exist
• 409 （conflict）- Generic conflict
• 500 （internal server error）- General error response
• 503 （Service Unavailable）- The server is currently unable to process the request

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“ client / Form of server ”, Built on a distributed system , Communicate over the Internet , With high delay （high latency）、 High concurrency .

How to develop software used in Internet Environment .

RESTful framework , Is the most popular Internet software architecture . Represent layer state transformation

It has a clear structure 、 Meet the standard 、 Easy to understand 、 Easy to expand , So more and more websites are using .

R resources ：

REST The name of " Represent layer state transformation " in , Omit the subject .“ The presentation layer " In fact, it means " resources ”（Resources） Of " The presentation layer ".

** So-called " resources ", It's an entity on the Internet , Or a specific information on the Internet .** It can be a piece of text 、 A picture 、 A song 、 A service , In a word, it is a concrete reality . You can use one URI（ Uniform resource locator ） Pointing to it , Each resource corresponds to a specific URI. To get this resource , Visit its URI Can , therefore URI It becomes the address or unique identifier of each resource .

R The presentation layer representation：

" resources " It's an information entity , It can have many external forms . We put " resources " In the form of , It's called it " The presentation layer "（Representation）

URI Entities that represent resources only , Does not represent its form . Strictly speaking , Some of the last ".html" Suffixes are unnecessary , Because this suffix means format , Belong to " The presentation layer " Category , and URI It should only represent " resources " The location of . Its concrete manifestation , belong HTTP The requested header information uses Accept and Content-Type Field assignment , These two fields are right " The presentation layer " Description of .

State transformation State Transfer:

Internet communication protocol HTTP agreement , It's a stateless protocol . It means , All States are saved on the server side . therefore , If the client wants to operate on the server , By some means , Let it happen on the server side " State transformation "（State Transfer）. And this transformation is based on the presentation layer , So is " Represent layer state transformation ".

The means used by the client , Can only be HTTP agreement . say concretely , Namely HTTP In the agreement , Four verbs for operation ：GET、POST、PUT、DELETE. They correspond to four basic operations ：GET Used to obtain resources ,POST Used to create a new resource （ Can also be used to update resources ）,PUT Used to update resources ,DELETE Used to delete resources .

Summarize what is RESTful framework ：

（1） every last URI Represents a resource ;

（2） Between client and server , A layer of expression that conveys this resource ;

（3） Client through four HTTP Verb , Operate on the server-side resources , Realization " Represent layer state transformation ".