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 describe how to call an API. The obtained token is used to authenticate the calling of other APIs.

Request URI

A request URI consists of the following:

{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 separately transmitted, rather than being conveyed in a request message separately.

**Table 1** URI parameter description
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 endpoint. The endpoint varies depending on services and regions. It can be obtained from the administrator. For example, the endpoint of IAM in the EU-Dublin region is iam.eu-west-101.myhuaweicloud.eu.
resource-path	Access path of an API for performing a specified operation. Obtain the path from the URI of the API. For example, the resource-path of the API for obtaining a user token is /v3/auth/tokens.
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". For example, ? limit=10 indicates that up to 10 data records will be displayed.

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 a server to return specified resources.
PUT	Requests a server to update specified resources.
POST	Requests a server to add a resource or perform a special operation.
DELETE	Requests a server to delete a specified resource (for example, an object).

For example, in the URI for obtaining a user token, the request method is POST. The request is as follows:

POST https://iam.eu-west-101.myhuaweicloud.eu/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, add Content-Type that defines a request body type to request for authentication information.

Table 3 lists common request header fields.

**Table 3** Common request headers
Parameter	Description	Mandatory	Example Value
Content-Type	MIME type of the request body. Use the default value application/json. For APIs used to upload objects or images, the value varies depending on the flow type.	Yes	application/json
Content-Length	Length of the request body. The unit is byte.	This field is optional for POST requests, but must be left blank for GET requests.	3495
X-Project-Id	Project ID. To obtain the project ID, see Obtaining a Project ID.	No	e9993fc787d94b6c886cbaa340f9c0f4
X-Auth-Token	User token. After a request is processed, the value of X-Subject-Token in the header is the token value.	Yes	The following is part of an example token: MIIPAgYJKoZIhvcNAQcCo...ggg1BBIINPXsidG9rZ

The API used to obtain a user token does not require authentication. Therefore, this API only requires adding the Content-Type field. The following is an example request:

POST https://iam.eu-west-101.myhuaweicloud.eu/v3/auth/tokens
Content-Type: application/json

(Optional) Request Body

This part is optional. The request body is often sent in a structured format (for example, JSON or XML) as specified in the Content-Type header field. If the request body contains full-width characters, these characters must be coded in UTF-8.

Request bodies vary depending on APIs. Some APIs do not require a request body, such as the APIs requested using the GET and DELETE methods.

For the API of obtaining a user token, request parameters and parameter description can be obtained from the API request. The following is an example request with a body included. Replace username, domianname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project name) with required values. You can obtain the values from the administrator.

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 details, see Obtaining a User Token.

POST https://iam.eu-west-101.myhuaweicloud.eu/v3/auth/tokens
Content-Type: application/json

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

If all data required for the API request is available, you can send a request to call an API through curl, Postman, or coding. For the API of obtaining a user token, x-subject-token in the response header is the required user token. Then, this token can be used to authenticate the calling of other APIs.

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