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 is in the following format:

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

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

Table 1 URI parameter description
Parameter	Description
URI-scheme	Protocol used to transmit requests. All APIs use HTTPS.
Endpoint	Specifies the domain name or IP address of the server bearing the REST service endpoint. Obtain the value from Regions and Endpoints.
resource-path	API access path for performing a specified operation. Obtain the value 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. Not all APIs have a query parameter. 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 pieces of data is to be viewed.

Request Methods

HTTP-based request methods, which are also called operations or actions, specify the type of operations that you are requesting.

Table 2 HTTP methods
Method	Description
GET	Requests a server to return the 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, an object.

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

POST https://{{endpoint}}/v3/auth/tokens

Request Header

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

Table 3 lists common request header fields.

Table 3 Common request header fields
Name	Description	Mandatory	Example
Content-Type	Specifies the MIME type of the request body. You are advised to use the default value application/json. For APIs used to upload objects or images, the value can vary depending on the flow type.	Yes	application/json
Content-Length	Specifies the length of the request body. The unit is byte.	This parameter is optional for POST requests, but must be left blank for GET requests.	3495
X-Project-Id	Specifies the project ID. Obtain the project ID by following the instructions in Obtaining a Project ID.	No	e9993fc787d94b6c886cbaa340f9c0f4
X-Auth-Token	Specifies the user token. After the 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 request with the added Content-Type header is as follows:

POST https://{{endpoint}}/v3/auth/tokens
Content-Type: application/json

(Optional) Request Body

This part is optional. A request body is generally sent in a structured format (for example, JSON or XML), corresponding to Content-Type in the request header, and is used to transfer content other than the request header. If the request body contains full-width characters, these characters must be coded in UTF-8.

The request body varies according to the APIs. Certain APIs do not require the request body, such as the GET and DELETE APIs.

For the API used to obtain a user token, the request parameters and parameter description can be obtained in the API request. The following provides an example request with a body included. Replace username, domianname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project ID) with the actual values. Obtain the value from the Regions and Endpoints.

Note

scope specifies where a token takes effect. In the following example, the token takes effect only on the resources specified by the project ID. You can set the scope to an account or a project under an account. For details, see Obtaining a User Token.

POST https://{{endpoint}}/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 by a request is available, you can send the request to call an API through curl, Postman, or coding. For the API used to obtain a user token, x-subject-token in the response header is the desired user token. Then, you can use the token to authenticate the calling of other APIs.

Parent topic: Calling APIs

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