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:

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

**Table 1** Request URI
Parameter	Description
URI-scheme	Protocol used to transmit requests. All APIs use HTTPS.
Endpoint	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 Endpoints. For example, the endpoint of IAM in region CN-Hong Kong is iam.ap-southeast-1.myhuaweicloud.com. For example, the endpoint of IAM in the eu-west-0 region is iam.eu-west-0.prod-cloud-ocb.orange-business.com.
resource-path	Access path of an API for performing a specified operation. Obtain the value 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-string	Query parameter, which is optional. Ensure that a question mark (?) is included before a 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:

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

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.

**Table 2** HTTP methods
Method	Description
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.

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 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 3 describes common request headers.

**Table 3** Common request headers
Name	Description	Mandatory	Example Value
Content-type	Request body type or format. Its default value is application/json.	Yes	application/json
Content-Length	Length of the request body. The unit is byte.	No	3495
X-Project-Id	Project ID. This parameter is used to obtain the token for the project.	No	e9993fc787d94b6c886cbaa340f9c0f4
X-Auth-Token	User token, which is a response to the API used to obtain a user token. This API is the only one that does not require authentication.	Yes	-
X-Language	Request language.	Yes	en_us
x-sdk-date	Time when the request is sent. The time is in YYYYMMDD'T'HHMMSS'Z' format. The value is the current Greenwich Mean Time (GMT) time of the system.	No	20190407T101459Z
Host	Information about the requested server. The value can be obtained from the URL of the service API in hostname[:port] format. If the port number is not specified, the default port is used. The default port number for https is 443.	No	code.test.com or code.test.com:443

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

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.

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.

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

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

The scope parameter specifies where a token takes effect. Its value can be project or domain. In the example, the value is project, indicating that the obtained token takes effect only for the resources in a specified project. If the value is domain, the obtained token takes effect for all resources of the specified account.

For more information about this parameter, see Obtaining a User Token.

If all data required for the API request is available, you can send the request to call an 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.

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