Updated on 2022-10-13 GMT+08:00

Making an API Request

This section describes how a REST API is formed and uses the IAM API for obtaining a user token as an example to describe how to call an API. A token authenticates 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 the request header, most programming languages and frameworks require the request URI to be transmitted separately.

Table 1 URI 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 CN North-Beijing1 region is iam.cn-north-1.myhuaweicloud.com.

resource-path

The access path of an API for performing a specified operation. Obtain the path 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

(Optional) Query parameter. Not all APIs have a query parameter. 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 a maximum of 10 data records will be displayed.

For example, to obtain an IAM token in the CN North-Beijing1 region, obtain the endpoint of IAM (iam.cn-north-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:

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https://iam.cn-north-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

HTTP defines the following request modes that can be used to send a request to the server:
Table 2 HTTP-defined request 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, the PATCH method may create one.

For example, in the case of the API used to obtain a user token, the request method is POST. The request is as follows:

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POST https://iam.cn-north-1.myhuaweicloud.com/v3/auth/tokens

Request Headers

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 lists common request header fields.
Table 3 Common request headers

Name

Description

Mandatory

Example

Host

Server domain name and port number of the resource being requested. 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 443.

No

This parameter is mandatory for AK/SK-based authentication.

code.test.com

or

code.test.com:443

Content-Type

MIME type of the response 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.

No

3495

X-Project-Id

Specifies a project ID. Obtain the project ID by following the instructions in Obtaining a Project ID.

No

This field is mandatory for requests that use AK/SK-based authentication in the DeC scenario or multi-project scenario.

e9993fc787d94b6c886cbaa340f9c0f4

X-Auth-Token

Specifies the user token.

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.

After the request is processed, the value of X-Subject-Token in the header is the token value.

No

This field is mandatory for token-based authentication.

The following is part of an example token:

MIIPAgYJKoZIhvcNAQcCo...ggg1BBIINPXsidG9rZ

In addition to supporting token-based authentication, cloud service APIs also support authentication using the 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-based Authentication" in Authentication.

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:

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

(Optional) Request Body

This part is optional. The body of a request is often sent in a structured format (for example, JSON or XML) as specified in the Content-Type header field. The request body transfers content except the request header. The request body can contain Chinese characters in the UTF-8 encoding format.

The request body varies depending on APIs. Some APIs do not require the request body, for example, 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. Replace username, domainname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project ID) with the actual values. To learn how to obtain a project ID, see Obtaining a Project ID.

The scope parameter specifies where a token will take 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 more information about this API, see Obtaining a User Token.

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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": {
                "id": "xxxxxxxxxxxxxxxxxx"
            }
        }
    }
}

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. You can use this token to authenticate the calling of other APIs.