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Making an API Request

This section describes the structure of a REST API, and uses the IAM API for obtaining a user token as an example to demonstrate how to call an API. The obtained token can then be used to authenticate the calling of other APIs.

A request consists of the request URL, request method, request header, and request body, which will be elaborated in this section. A request example is as follows:

Figure 1 Example request

Request URI

A request URI is in the following format:

{URI-scheme} :// {Endpoint} / {resource-path} ? {query-string}

Although a request URI is included in the request header, most programming languages or frameworks require the request URI to be transmitted separately.

  • URI-scheme: Protocol used to transmit requests. All APIs use HTTPS.
  • Endpoint: Domain name or IP address of the server bearing the REST service endpoint. Obtain the value from Regions and Endpoints. For example, the endpoint of IAM in region CN North-Beijing1 is iam.cn-north-1.myhuaweicloud.com.
  • resource-path: Access path of an API for performing a specified operation. Obtain the path from the URI of an API. For example, the resource-path of the text classification API used to obtain a user token is /v1/{project_id} /nlu/classification. {project_id} indicates the project ID. For details about how to obtain the project ID, see Obtaining a Project ID.
  • query-string: Query parameter, which is optional. Ensure that a question mark (?) is included before each query parameter that is in the format of "Parameter name=Parameter value". This parameter is not used.

For example, to call the text classification API in the CN North-Beijing4 region, obtain the endpoint of NLP (nlp-ext.cn-north-4.myhuaweicloud.com)) for this region and the resource-path (/v1/{project_id}/nlu/classification) in the URI of the text classification API. Then, construct the URI as follows:

https://nlp-ext.cn-north-4.myhuaweicloud.com/v1/{project_id}/nlu/classification
Figure 2 Example URI

To simplify the URI display in this document, each API is provided only with a resource-path and a request method. The URI-scheme of all APIs is HTTPS, and the endpoints of all APIs in the same region are identical.

Request Methods

The HTTP protocol defines the following request methods that can be used to send a request to the server:

  • GET: requests the server to return specified resources.
  • PUT: requests the server to update specified resources.
  • POST: requests the server to add resources or perform special operations.
  • DELETE: requests the server to delete specified resources, for example, an object.
  • HEAD: same as GET except that the server must return only the response header.
  • PATCH: requests the server to update partial content of a specified resource. If the resource does not exist, a new resource will be created.

In the URI of the text classification API, the request method is POST. The request is as follows:

POST https://nlp-ext.cn-north-4.myhuaweicloud.com/v1/{project_id}/nlu/classification

Request Header

You can also add additional header fields to a request, such as the fields required by a specified URI or HTTP method. For example, to request for the authentication information, add Content-Type, which specifies the request body type.

Common request header fields are as follows:

  • Content-Type: specifies the request body type or format. This field is mandatory and its default value is application/json. Other values of this field will be provided for specific APIs if any.
  • X-Auth-Token: specifies a user token only for token-based API authentication. NLP uses token-based authentication. For details about the user token, see section Authentication.

The following provides an example request with a request header included.

POST https://nlp-ext.cn-north-4.myhuaweicloud.com/v1/{project_id}/nlu/classification
 
Content-Type: application/json
x-auth-token: MIIaBgYJKoZIhvcNAQcC...

Request Body

The body of a request is often sent in a structured format as specified in the Content-Type header field. The request body transfers content except the request header. The request body varies between APIs. Some APIs do not require the request body, such as the APIs requested using the GET and DELETE methods.

For the text classification API, obtain the request parameters and parameter description in the API request. The following provides an example request with a body included.

POST https://nlp-ext.cn-north-4.myhuaweicloud.com/v1/{project_id}/nlu/classification
 
Content-Type: application/json
x-auth-token: MIIaBgYJKoZIhvcNAQcC...
{    
     "content":"XXX Anti-Dandruff Shampoo, free delivery within the country",
     "domain":1
}

If all data required for the API request is available, you can send the request to call the API through curl, Postman, or coding. For the text classification API, obtain the request parameters and parameter description in the API request.

Parent topic: Calling APIs