Updated on 2023-06-26 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

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

A request URI consists of four parts: {URI-scheme} :// {Endpoint} / {resource-path}? {query-string}

The following table describes the parameters.

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 Regions and Endpoints.

For example, the endpoint of IAM in the AP-Singapore region is iam.ap-southeast-3.myhuaweicloud.com.

resource-path

The resource path, that is, the API access path, is obtained from the URI of a specific API. For example, the resource-path of the API used to obtain a user token is /v3/auth/tokens.

query-string

(Optional) Query a parameter. The query parameter is prefixed with a question mark (?), in the format of Parameter name=Parameter value. For example, limit=10 indicates that a maximum of 10 data records will be queried.

Example: To obtain the token of IAM in the AP-Singapore region, use the endpoint (iam.ap-southeast-3.myhuaweicloud.com), find resource-path (/v3/auth/tokens) in the URI of Obtaining a User Token, and combine it as follows:

https://iam.ap-southeast-3.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

HTTP defines the following request methods that can be used to send a request to the server. The details are as follows:

Request 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.

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-3.myhuaweicloud.com/v3/auth/tokens

Request Header

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

Common request header fields:

Name

Description

Mandatory

Remarks

Content-Type

Request body type or format

Yes

The default value is application/json. Other values of this field will be provided for specific APIs if any.

X-Auth-Token

User token

Optional

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.

X-Project-ID

Subproject ID

Optional

Used in multi-project scenarios.

X-Domain-ID

Specifies an account ID.

-

-

In addition to supporting token-based authentication, public cloud APIs also support authentication using 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 Authentication.

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

POST https://iam.ap-southeast-3.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

Request Body

A request body is generally sent in structured format. It corresponds to Content-Type in the request header and transfers content except the request header.

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

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 example request has a body included. Replace username, domainname, ********, and xxxxxxxxxx with the actual values. username indicates the username, domainname indicates the name of the account to which the user belongs, ******** indicates the login password, and xxxxxxxxxx indicates the project name, such as ap-southeast-3. You can obtain the value from Regions and Endpoints.

The scope parameter specifies where a token takes effect. 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.cn-north-1.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

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

If all data required for the API 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.