如何使用Azure Function以POST方式调用外部API并传递请求体参数

基于原有HttpWebRequest的修改版本 #

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.Net;
using System.IO;
using System.Text.Json;

namespace FunctionRestApi
{
    // 定义外部API请求参数封装类
    public class ExternalApiRequest
    {
        public string sub_user_id { get; set; }
        public string start_date { get; set; }
        public string end_date { get; set; }
    }

    public static class Function1
    {
        [FunctionName("Function1")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            // 可选：如果参数需要从调用当前Function的请求中获取，打开下方注释读取
            // string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            // var inputParam = JsonSerializer.Deserialize<ExternalApiRequest>(requestBody);

            // 构造调用外部API的请求参数
            var apiParam = new ExternalApiRequest
            {
                sub_user_id = "实际的用户ID",
                start_date = "2024-01-01",
                end_date = "2024-01-31"
                // 如果用上面读取的传入参数，这里就赋值为inputParam对应的属性即可
            };

            var httpWebRequest = (HttpWebRequest)WebRequest.Create("URL_with_client_id_authorization_token");
            httpWebRequest.ContentType = "application/json";
            // 请求方法改为POST
            httpWebRequest.Method = "POST";

            // 序列化参数并写入POST请求体
            var jsonParam = JsonSerializer.Serialize(apiParam);
            using (var requestStream = httpWebRequest.GetRequestStream())
            using (var streamWriter = new StreamWriter(requestStream))
            {
                await streamWriter.WriteAsync(jsonParam);
                await streamWriter.FlushAsync();
            }

            string result = string.Empty;
            var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
            using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
            {
                result = await streamReader.ReadToEndAsync();
                log.LogInformation(result);
            }

            // 修复返回值，返回外部API的实际响应内容
            return new OkObjectResult(result);
        }
    }
}

核心修改说明 #

• 新增ExternalApiRequest类封装需要传递的三个业务参数，方便JSON序列化操作，参数类型可根据实际业务要求调整为DateTime、int等对应类型
• 将外部API请求方法从GET调整为POST
• 新增请求体写入逻辑，把序列化后的JSON参数写入POST请求的请求流中
• 调整方法为异步实现，避免同步IO阻塞导致的性能问题，更适配Azure Function的运行环境
• 修复原有返回值错误，改为返回外部API的实际响应内容
• 提供了从当前Function触发请求中读取参数的可选实现，如果你需要调用方把参数传给Function再透传给外部API，直接打开对应注释即可使用

更推荐的实现方式（HttpClient版本） #

HttpWebRequest已经被官方标记为过时，更推荐使用HttpClient配合IHttpClientFactory使用，避免端口耗尽问题，核心调用逻辑示例如下：

// 注入HttpClient，Program.cs中添加builder.Services.AddHttpClient();
public static class Function1
{
    [FunctionName("Function1")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
        ILogger log,
        IHttpClientFactory httpClientFactory)
    {
        var client = httpClientFactory.CreateClient();
        client.DefaultRequestHeaders.Add("Authorization", "你的认证Token");
        
        var apiParam = new ExternalApiRequest
        {
            sub_user_id = "实际的用户ID",
            start_date = "2024-01-01",
            end_date = "2024-01-31"
        };

        var response = await client.PostAsJsonAsync("外部API地址", apiParam);
        response.EnsureSuccessStatusCode();
        var result = await response.Content.ReadAsStringAsync();
        log.LogInformation(result);

        return new OkObjectResult(result);
    }
}

内容的提问来源于stack exchange，提问作者new_bie_new