Understanding the RESTful architecture

More and more people are beginning to realize that the website is software , and it is a new kind of software.

This "Internet Software" uses the client/server model, which is built on the distributed system and communicates with the Internet, which has the characteristics of high latency (hi latency) and high concurrency.

Website development, can adopt the model of software development completely. But traditionally, the software and the network are two different fields, seldom have the intersection, the software development is mainly for the single machine environment, the network mainly studies the communication between the system. The rise of the Internet has enabled these two areas to converge, and now we have to consider how to develop the software used in the Internet environment.

The restful architecture is one of the most popular Internet software architectures available. Its structure is clear, conforms to the standard, easy to understand, expands conveniently, therefore is getting more and more website adoption.

However, what is a restful architecture is not an easy question to be clear about. Below, I'll talk about the restful architecture I understand.

First, origin

The word rest is from Roy Thomas Fielding in his 2000 doctoral dissertation.

Fielding is a very important person who is the main designer of the HTTP protocol (version 1.0 and 1.1), one of the authors of the Apache server Software, and the first president of the Apache Foundation. As a result, the publication of his paper has attracted much attention and has had a profound impact on the development of the Internet.

He introduces the purpose of writing this paper:

This paper studies the intersection of two frontier----software and network----of computer science. For a long time, software research focuses on the classification of software design, the evolution of design methods, rarely objectively evaluate the impact of different design choices on system behavior. On the contrary, network research focuses on the details of communication behavior between systems, how to improve the performance of specific communication mechanisms, and often ignores the fact that changing the interactive style of the application is more important than changing the interactive protocol and the overall performance. The purpose of my writing is to understand and evaluate the architecture design of network-based application software in accordance with the principle of architecture, and get a powerful, good performance and suitable communication architecture. "

(This dissertation explores a junction on the frontiers of the both the disciplines in computer Science:software and NETW Orking. Software have long been concerned with the categorization of software designs and the development of design method Ologies, but had rarely been able to objectively evaluate the impact of various design choices on system behavior. Networking, in contrast, was focused on the details of generic communication behavior between systems and Improvin G The performance of particular communication techniques, often ignoring the fact that changing the interaction style of a N application can has more impact on performance than the communication protocols used for that interaction. My work was motivated by the desire to understand and evaluate the architectural design of network-based application Softwa Re through principled use of architectural constraints, thereby obtaining the functional, performance, and social Properti Es desired of an architecture. )

Second, the name

Fielding his architectural principles of Internet software, named rest, the abbreviation of representational state transfer. My translation of this phrase is "presentation layer State transformation".

If a schema conforms to the rest principle, it is called a restful architecture.

The best way to understand the restful architecture is to understand what the phrase representational state transfer means, and what each word represents. If you understand the name, it's easy to see what kind of design rest is.

III. Resource (resources)

The name of rest, "presentation Layer State Transformation", omits the subject. The "presentation layer" actually refers to the "presentation layer" of resources.

The so-called "resources", is an entity on the network, or is a specific information on the network. It can be a piece of text, a picture, a song, a service, in short, a specific entity. You can point to it with a URI (Uniform Resource Locator), and each resource corresponds to a specific URI. To get this resource, access its URI so that the URI becomes the address of each resource or a unique identifier.

The so-called "surfing the Internet" is to interact with a series of "resources" on the Internet and invoke its URI.

Iv. Presentation layer (representation)

A "resource" is an information entity that can have a variety of external representations. we take the form of "resources" specifically, called its "presentation Layer" (representation).

For example, text can be expressed in TXT format, can also be used in HTML format, XML format, JSON format, and even binary format can be used, images can be in JPG format, can also be used in PNG format.

The URI represents only the entity of the resource and does not represent its form. Strictly speaking, some URLs last ". html" suffix is unnecessary, because this suffix name represents the format, which belongs to the "presentation layer" category, and the URI should only represent the location of the "resource". Its specific representation should be specified in the header information of the HTTP request with the Accept and Content-type fields, which is the description of the "presentation layer".

V. State transformation (Transfer)

Accessing a Web site represents an interactive process between the client and the server. In this process, data and state changes are bound to be involved.

The Internet Communication Protocol HTTP protocol is a stateless protocol. This means that all States are saved on the server side. Therefore, if the client wants to operate the server, there must be some way to make the server side "state Transfer". And this transformation is based on the expression layer, so is the "Expression Layer state transformation."

The method that the client uses, can only be the HTTP protocol. Specifically, there are four verbs in the HTTP protocol that represent the mode of operation: GET, POST, PUT, DELETE. They correspond to four basic operations:get is used to get a resource, post is used to create a new resource (and can also be used to update resources), put is used to update resources, and delete is used to delete resources.

Vi. Summary of

Combining the above explanations, we summarize what a restful architecture is:

(1) Each URI represents a resource;

(2) A representation layer (representation) between the client and the server that transmits this resource;

(3) The client through four HTTP verbs, the server-side resources to operate, to achieve "performance layer State transformation."

Seven, misunderstanding

The restful architecture has some typical design pitfalls.

one of the most common design errors is that the URI contains verbs. because "resource" represents an entity, it should be a noun, the URI should not have verbs, the verb should be placed in the HTTP protocol.

For example, a URI is/POSTS/SHOW/1, where show is a verb, the URI is wrong, the correct wording should be/posts/1, and then the show is represented by a GET method.

If certain actions are not represented by an HTTP verb, you should make the action a resource. such as online remittance, from account 1 to account 2 remittance 500 yuan, the wrong URI is:

Post/accounts/1/transfer/500/to/2

The correct way of writing is to change the verb transfer to a noun transaction, the resource cannot be a verb, but it can be a service:

Post/transaction http/1.1
host:127.0.0.1
　　
from=1&to=2&amount=500.00

Another design mistake is to include the version number in the URI :

Http://www.example.com/app/1.0/foo

Http://www.example.com/app/1.1/foo

Http://www.example.com/app/2.0/foo

Because different versions can be understood as different representations of the same resource, the same URI should be used. The version number can be distinguished in the Accept field of the HTTP request header information (see Versioning REST Services):

Accept:vnd.example-com.foo+json; version=1.0

Accept:vnd.example-com.foo+json; version=1.1

Accept:vnd.example-com.foo+json; version=2.0

http://kb.cnblogs.com/page/114905/

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