Question

我正在使用HttpClient的单例实例进行调用。我想知道有没有办法测试HttpClient是否有效？在应用程序的生命周期中，这个HttpClient实例是否会变坏，因为需要创建一个新实例。我的代码如下

public class HttpClientWrapper : IHttpClientWrapper
{
    private Uri _baseAddress;
    private int _connectionTimeout;
    private HttpClient _httpClientInstance;
    private HttpClient HttpClientInstance
    {
        get
        {
            if (_httpClientInstance == null)
                _httpClientInstance = CreateHttpClient();
            return _httpClientInstance;
        }
    }
    public HttpClientWrapper(Uri baseAddress, int connectionTimeout)
    {
        _baseAddress = baseAddress;
        _connectionTimeout = connectionTimeout;
    }
    public Task<HttpResponseMessage> PostAsJsonAsync<T>(string requestUri, T      value)
    {
       //Test the instance before using it. What should be the test??
       return HttpClientInstance.PostAsJsonAsync<T>(requestUri, value);
    }

    private HttpClient CreateHttpClient()
    {
        HttpClientHandler handler = new HttpClientHandler()
        {
            UseDefaultCredentials = true
        };
        HttpClient client = new HttpClient(handler);
        client.Timeout = TimeSpan.FromMilliseconds(_connectionTimeout);
        client.BaseAddress = _baseAddress;
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new  MediaTypeWithQualityHeaderValue("application/json"));
        return client;
    }
}

Answer 1

HttpClient旨在重用。它与WCF和ChannelFactory的旧时代不同，其中频道可能处于故障状态并且必须重新创建。

HttpClient 旨在实例化一次并在应用程序的整个生命周期中重复使用。特别是在服务器应用程序中，为每个请求创建一个新的HttpClient实例将耗尽重负载下可用的套接字数量。这将导致SocketException错误。

参考：https://www.asp.net/web-api/overview/advanced/calling-a-web-api-from-a-net-client

Singleton HttpClient处理

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