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At present, as the standard connection between most mobile app and cloud service backend, REST API has been recognized by most developers and widely used. In recent years, with the gradual rise of the emerging API economic model, many manufacturers have opened their backstage business capabilities as REST API for a wider range of third-party developers to use.

However, managing REST API is not an easy task. Due to the lack of effective interface data schema constraints, the arrangement of resource endpoint when designing REST API and the ways to send http requests are varied, after the completion of REST API development, API developers still need to write API documents manually in most cases, so that users can connect according to the instructions in the document. And the document needs to be rewritten when the API changes, which is time-consuming and error-prone. For example, an REST API document must at least list the following basic information:

* name of API

* URL resource path where API is located

* http request method (GET, POST, PUT, etc.)

* how API submits data (query parameters, form submission, JSON submission, etc.)

* format of data returned by calling API

In the REST API information provided above, in most cases, the JSON data returned from API can only use "examples" to illustrate the structure of the data, but cannot accurately express the exact meaning and type definition of each field in this piece of JSON data. This is all due to the lack of schema definition of JSON data in REST API, and this way of "giving examples" is undoubtedly a very helpless and silly approach. When we connect with the interfaces of other vendors during development, it often occurs that the other party's documents are not clear, and we need to manually confirm the communication, or even check whether our understanding of a certain data parameter or the returned result is correct. This is a very time-consuming and labor-consuming task.

When the business changes and any of the previous information about REST API changes, such as adding a new field to the returned result, the developer has to rewrite the document by hand, and then resend the document to the API user for change. The above process will be very painful if repeated iterations. Although there are some API design and documentation tools, such as Swagger UI, which make it easier for developers to write documents in the Yaml language, they do not eliminate the complexity inherent in REST API.

This API management solution perfectly solves the above REST API document problem. CDIF is the world's first JSON-based SOA solution. REST API managed by CDIF can automatically generate their API documents, which greatly saves developers' time and energy in managing API documents. The framework design of CDIF can be represented by the following figure:

In the figure above, CDIF uniformly encapsulates REST API into various driver packages, each of which is a standard node.js npm package. Each driver package can contain any number of REST API access codes. In the implementation of the driver package, according to the specifications provided by CDIF, each REST API must provide a unified and general API model for the client. The API model is an JSON document that contains all the information about how to access the API. Compared to the above REST API document, this API model contains only the following information:

* name of API

* JSON schema definition of API input parameters and returned results

Other information about REST API is seen as the internal implementation of the API driver package and does not need to be exposed to external API users.

The API model based on CDIF definition specification has API descriptions with the same capabilities as XML-based WSDL. On this basis, the API management tool matched with CDIF can automatically parse the JSON document and automatically generate the document from which it manages the REST API. The following is a screenshot of a clear and easy-to-read SMS API document automatically generated in the API market using CDIF:

In the above API document, all the types, descriptions, constraints, API error messages of each field in the request and return data are automatically generated from the JSON schema file provided by the user in the API package, and the API and data are described 100% accurately. Developers only need to write the API model according to the specification definition provided by CDIF and upload a npm package containing only dozens of lines of API access code to the CDIF-based API management platform to have this capability. When the API parameter or the returned result needs to be updated, users only need to update the contents of the JSON schema file in the npm package, re-upload and automatically get the new API document.

When accessing the REST API managed by CDIF, the user only needs to access a fixed URL address provided by CDIF for the managed REST API, and the client only needs to support the http POST method to submit the API request data. All submitted data, in accordance with JSON schema constraints, is placed in the http request and the returned JSON body. This design is the classic implementation of WSDL + SOAP, which is very easy to use and has good compatibility. At the same time, with the help of the strong performance ability of JSON schema, CDIF can support API interface data of any complexity. At present, most popular development languages support the submission of API requests by means of post JSON data, so the API access interface provided by CDIF has been supported by the most extensive client development environment. In the future, we will add the automatic generation of client-side API access codes in various languages, so that API users only need to copy and paste the code to access it, further simplifying the process of convenient API development and use.

In addition, when the internal implementation of the API package needs to change, the user only needs to modify the code of the API package, re-upload and deploy the new version with one click. CDIF supports hot switching of API package code without even affecting the online invocation of older versions of API. This greatly facilitates and simplifies the API development experience of developers.

Moreover, after uploading the API package, developers can automatically have an API test page, which makes it easier for API developers and API users to debug the usability of API. For this feature, please refer to the next article: API Test Automation-the basic function of SOA based on CDIF.

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