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.

  • 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. Different services have different endpoints in different regions. Obtain the value from Regions and Endpoints.For example, the endpoint of IAM in region CN North-Beijing1 is iam.cn-north-1.myhuaweicloud.com.
  • 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.

For example, to obtain the IAM token in region CN North-Beijing1, obtain the endpoint (iam.cn-north-1.myhuaweicloud.com) of this region and the resource-path (/v3/auth/tokens) in the URI of the API, which is used for obtaining a user token. Then, assemble these fields as follows:

https://iam.cn-north-1.myhuaweicloud.com/v3/auth/tokens
Figure 1 Example URI

To simplify the URI display, each API is provided with only a resource-path and a request method. This is because the URI-scheme value of all APIs is HTTPS, and the endpoints in a region are the same. Therefore, the two parts are omitted.

Request Methods

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

  • GET: Requests the server to return specified resources.
  • PUT: Requests the server to update specified resources.
  • POST: Requests the server to add a resource or perform special operations.
  • DELETE: Requests a server to delete specified resources, for example, an object.
  • HEAD: Requests a server resource header.
  • PATCH: Requests the server to update the partial content of a specified resource. If the resource is unavailable, the PATCH method is used to create a resource.

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

POST https://iam.cn-north-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 an HTTP method. For example, add Content-Type that defines a request body type to request for the authentication information.

Common request headers are as follows:

Table 1 Common request headers

Parameter

Mandatory

Description

Example

Content-Type

Yes

Specifies the request body type or format. This field is mandatory and its default value is application/json. For other values, the description will be provided for specific APIs.

application/json

X-Auth-Token

This parameter is mandatory only for authentication using tokens.

Specifies the user token. It is a response to the API for obtaining a user token (only this API does not require authentication).

-

X-Project-ID

No

Specifies a sub-project ID. It is mandatory in multi-project scenarios to obtain tokens for different projects.

e9993fc787d94b6c886cbaa340f9c0f4

Authorization

This header field is mandatory if AK/SK authentication is in use.

Specifies the signature authentication information. The value can be obtained from the request signing result.

-

X-Sdk-Date

This header field is mandatory if AK/SK authentication is in use.

Specifies the time when the request is sent. The time is in YYYYMMDD'T'HHMMSS'Z' format.

The value is the current Greenwich Mean Time (GMT) of the system.

20150907T101459Z

Host

This header field is mandatory if AK/SK authentication is in use.

Specifies the information about the requested server. The value can be obtained from the URL of the service API. The value is hostname[:port]. If the port number is not specified, the default port is used. The default port number for https is port 443.

code.test.com

or

code.test.com:443

Content-Length

This field is mandatory for POST and PUT requests, but must be left blank for GET requests.

Indicates the length of the request body. The unit is byte.

3495

X-Language

No

Specifies the request language, which value can be:

  • zh-cn: Chinese
  • en-us: English

en-us

In addition to supporting authentication using tokens, the public cloud APIs support authentication using AK/SK, which uses SDKs to sign a request. During the signature, the Authorization (signature authentication) and X-Sdk-Date (time when a request is sent) headers are automatically added in the request.

The API for obtaining 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://iam.cn-north-1.myhuaweicloud.com/v3/auth/tokens  Content-Type: application/json

Request Body

A request body is generally sent in a structured format. It corresponds to Content-Type in the request header and transfers data except for the request header. If the request body contains Chinese 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 of obtaining a user token, obtain the request parameters and parameter description in the API request. The following provides an example request with a body included. Replace username, domainname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project ID) with the actual values. Obtain a project ID from Regions and Endpoints, for example, cn-north-1.

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 scope to an account or a project under an account. For details, see Obtaining a User Token.

POSThttps: //iam.cn-north-1.myhuaweicloud.com/v3/auth/tokensContent-Type: application/json{
    "auth": {
        "identity": {
            "methods": [
                "password"
            ],
            "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 an API through curl, Postman, or coding. For the API of obtaining 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.