单例httpclient与创建新的httpclient请求

Question

null

在第一种方法中，我在mobile Applicaiton发出的每个新请求中创建新的http客户机对象。

这是我的代码

  public HttpClient GetConnection()
        {

            HttpClient httpClient = new HttpClient();
            httpClient.BaseAddress = new Uri(baseAddress); 
            httpClient.Timeout = System.TimeSpan.FromMilliseconds(timeout);


            return httpClient;

        }

邮递请求代码

 public async Task<TResult> PostAsync<TRequest, TResult>(String url, TRequest requestData)
        {
            HttpClient client = GetConnection();
            String responseData = null;
            if (client != null)
            {

                String serializedObject = await Task.Run(() => JsonConvert.SerializeObject(requestData, _jsonSerializerSettings));
                var jsonContent = new StringContent(serializedObject, System.Text.Encoding.UTF8, "application/json");
                HttpResponseMessage response = await client.PostAsync(new Uri(url, UriKind.Relative), jsonContent);
                responseData = await HandleResponse(response);


                return await Task.Run(() => JsonConvert.DeserializeObject<TResult>(responseData, _jsonSerializerSettings));


            }
            else
            {

                throw new NullReferenceException("NullReferenceException @ PostAsync  httpclient is null WebRequest.cs");

            }

        }

new LoginService(new WebRequest()).UserLogin(userRequest);

_webRequest.PostAsync<UserRequest,bool>(Constants.USER_LOGIN, userRequest);

private static readonly Lazy<HttpService> lazy =
        new Lazy<HttpService>(() => new HttpService());

        public static HttpService Instance { get { return lazy.Value; } }



        private HttpClient getConnection()
        {

            client = new HttpClient();
            client.Timeout = System.TimeSpan.FromMilliseconds(timeout);

            //client.MaxResponseContentBufferSize = 500000;
            client.BaseAddress = new Uri(baseAddress);
            return client;
        }

public Task<HttpResponseMessage> sendData(String url,String jsonData)
        {

            var jsonContent = new StringContent(jsonData, System.Text.Encoding.UTF8, "application/json");

            return getConnection().PostAsync(new Uri(url, UriKind.Relative), jsonContent);
        }

HttpService.Instance.sendData(...)

Answer 1

更新：使用HttpClient的单个静态实例似乎不尊重DNS更改，因此解决方案是使用HttpClientFactory。请参阅这里的Microsoft文档。

要使用HttpClientFactory，必须使用Microsoft的依赖项注入。这是ASP.NET核心项目的默认值，但对于其他项目，必须引用Microsoft.Extensions.HTTP和Microsoft.Extensions.DependencyInject。

然后，在创建服务容器时，只需调用AddHttpClient():

var services = new ServiceCollection();
services.AddHttpClient()
var serviceProvider = services.BuildServiceProvider();

单例是使用HttpClient的正确方法。请看这篇文章的全部细节。

Microsoft文档状态：

HttpClient只需实例化一次，并在应用程序的整个生命周期中重用。为每一个请求实例化一个HttpClient类将耗尽在繁重负载下可用的套接字数量。这将导致SocketException错误。下面是一个正确使用HttpClient的示例。