Updated on 2023-01-17 GMT+08:00

Making an API Request

This section describes the structure of a REST API request, 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.

Request URI

A request URI is in the following format:


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

Table 1 Parameters in a URI




Protocol used to transmit requests. All APIs use HTTPS.


Domain name or IP address of the server bearing the REST service. The endpoint varies between services in different regions. It can be obtained from Regions and Endpoints.

For example, the endpoint of IAM in the CN-Hong Kong region is iam.ap-southeast-1.myhuaweicloud.com.


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 API used to obtain a user token is /v3/auth/tokens.


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. For example, ? limit=10 indicates that a maximum of 10 data records will be displayed.

For example, to obtain an IAM token in the CN-Hong Kong region, obtain the endpoint of IAM (iam.ap-southeast-1.myhuaweicloud.com) for this region and the resource-path (/v3/auth/tokens) in the URI of the API used to obtain a user token. Then, construct the URI as follows:

Figure 1 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 a server to return specified resources.
  • PUT: requests a server to update specified resources.
  • POST: requests a server to add resources or perform special operations.
  • DELETE: requests a server to delete specified resources, for example, objects.
  • HEAD: same as GET except that the server must return only the response header.
  • PATCH: requests a server to update a part of a specified resource. If the resource does not exist, a new resource can be created using the PATCH method.

For example, in the case of the API used to obtain a user token, the request method is POST. The request is as follows:

POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens

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.

Table 2 lists the common request header fields.

Table 2 Common request header fields




Example Value


Request server information, which is obtained from the URL of a service API. The value is in the format of Hostname:Port number. If no port is specified, the default port will be used. For HTTPS, port 443 is used by default.


This parameter is mandatory for AK/SK authentication.





Message body type or format. The default value application/json is recommended. Other values of this field will be provided for specific APIs if any.




Length of the request body. The unit is byte.




Project ID. Obtain the project ID by following the instructions in Obtaining a Project ID.


This field is mandatory for requests that use AK/SK authentication in the Dedicated Cloud (DeC) scenario or multi-project scenario.



User token.

The user token is a response to the API used to obtain a user token. This API is the only one that does not require authentication.

After the request is processed, the value of X-Subject-Token in the response header is the token value.


Mandatory for token-based authentication.

The following is part of an example token:


In addition to supporting token-based authentication, cloud service APIs also support authentication using the AK/SK. During AK/SK-based authentication, an SDK is used to sign the request, and the Authorization (signature information) and X-Sdk-Date (time when the request is sent) header fields are automatically added to the request.

For more information, see "AK/SK-based Authentication" in Authentication.

The API used to obtain a user token does not require authentication. Therefore, only the Content-Type field needs to be added to requests for calling the API. An example of such requests is as follows:

POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

Request Body (Optional)

The body of a request is often sent in a structured format as specified in the Content-type header field, such as JSON or XML. The request body transfers content except the request header.

A request body varies between APIs. Some APIs do not require the request body, such as the APIs requested using the GET and DELETE methods.

In the case of the API used to obtain a user token, the request parameters and parameter description can be obtained from the API request. The following provides an example request with a body included. Replace username, domainname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project name) with the actual values (for example, ap-southeast-1). The project name can be obtained from Regions and Endpoints.

The scope parameter specifies where a token takes effect. You can set scope to an account or a project under an account. In the following example, the token takes effect only for the resources in a specified project. For more information about this API, see Obtaining a User Token.

POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

    "auth": {
        "identity": {
            "methods": [
            "password": {
                "user": {
                    "name": "username",
                    "password": "********",
                    "domain": {
                        "name": "domainname"
        "scope": {
            "project": {
                "name": "xxxxxxxxxxxxxxxxxx"

If all data required by a request is available, you can send the request to call the API through curl, Postman, or coding. In the response to the API used to obtain a user token, x-subject-token is the desired user token. This token can then be used to authenticate the calling of other APIs.