在 AWS CDK 项目中使用 Python 编写代码来实现子域名的 CORS 策略。

首先，需要导入 AWS CDK 中的相关库和模块：

from aws_cdk import (
    aws_apigateway as apigateway,
    aws_lambda as lambda_,
    aws_iam as iam,
    core,
)

接着，创建自定义域名对象：

domain_name = apigateway.DomainName(
    self, "DomainName",
    domain_name=domain_name,
    certificate=certificate,
    security_policy=apigateway.SecurityPolicy.TLS_1_2
)

定义 API Gateway 的 rest API：

api = apigateway.RestApi(
    self, "APIGateway",
    rest_api_name="subdomain-cors-api",
    domain_name=domain_name,
    default_cors_preflight_options={
        "allow_origins": apigateway.Cors.ALL_ORIGINS, 
        "allow_methods": apigateway.Cors.ALL_METHODS, 
        "allow_headers": ["Content-Type", "X-Amz-Date", "Authorization", "X-Api-Key"]
    }
)

创建 Lambda 函数并添加到 API Gateway 中：

handler = lambda_.Function(
    self, "Handler",
    code=lambda_.Code.asset("lambda"),
    handler="handler.handle_request",
    runtime=lambda_.Runtime.PYTHON_3_8,
)

integration = apigateway.LambdaIntegration(
    handler=handler,
    proxy=True,
)

api.root.add_method(
    "ANY", 
    integration, 
    method_responses=[{
        "statusCode": "200",
        "responseParameters": {
            "method.response.header.Access-Control-Allow-Headers": True,
            "method.response.header.Access-Control-Allow-Methods": True,
            "method.response.header.Access-Control-Allow-Origin": True,
        }
    }], 
    integration_responses=[{
        "statusCode": "200",
        "responseParameters": {
            "method.response.header.Access-Control-Allow-Headers": "'Content-Type,X-Amz-Date,Authorization,X-Api-Key'",
            "method.response.header.Access-Control-Allow-Methods": "'