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为什么要定义接口而不直接使用静态类，因为接口可以注入缓存对象，这样就能从缓存中读取指定的请求头

using System;using System.Collections.Generic;using System.Net.Http;using System.Text;using System.Threading.Tasks;using Volo.Abp.Application.Services;namespace Test.Common{    /// 
    /// HTTP请求接口    /// 
    public interface IHttpClientUtils: IApplicationService    {        /// 
        /// 发送HTTP请求，注意Get请求第4个参数才是缓存key，因此第3个参数请设置为null        /// 
        /// HttpMethod.Get、HttpMethod.Post、HttpMethod.Put、HttpMethod.Delete        /// 完整地址        /// 请求体对象        /// 鉴权请求头缓存key        /// 请求头        ///         Task SendAsync(HttpMethod method, string url, object model = null, string cacheKey = "", Dictionary headers = null);        /// 
        /// 发送HTTP表单请求        /// 
        /// HttpMethod.Post、HttpMethod.Put        /// 完整地址        /// 请求体对象        /// 鉴权请求头缓存key        /// 请求头        ///         Task SendFormAsync(HttpMethod method, string url, object model, string cacheKey = "", Dictionary headers = null);    }}

1、支持https

2、支持从缓存读取鉴权请求头

3、支持对象携带文件上传

using Microsoft.Extensions.Logging;using Newtonsoft.Json;using RestSharp;using System;using System.Collections.Generic;using System.IO;using System.Linq;using System.Net;using System.Net.Http;using System.Net.Http.Headers;using System.Net.Security;using System.Security.Cryptography.X509Certificates;using System.Text;using System.Threading.Tasks;using Volo.Abp.Application.Services;using Volo.Abp.Caching;using Volo.Abp.Json;namespace Test.Common{    /// 
    /// HTTP请求实现    /// 
    public class HttpClientUtils: ApplicationService, IHttpClientUtils    {        private readonly ILogger _logger;        private readonly IDistributedCache> _cache;        public HttpClientUtils(            ILogger logger,            IDistributedCache> cache)         {            _cache = cache;            _logger = logger;        }        /// 
        /// 发送HTTP请求        /// 
        /// HttpMethod.Get、HttpMethod.Post、HttpMethod.Put、HttpMethod.Delete        /// 完整地址        /// 请求体对象        /// 鉴权请求头缓存key        /// 请求头        ///         public async Task SendAsync(HttpMethod method, string url, object model = null, string cacheKey = "", Dictionary headers = null)        {            _logger.LogInformation($"SendAsync {method.Method} url = {url}， cacheKey = {cacheKey}， data = {JsonConvert.SerializeObject(model)}");            try            {                using (var client = new HttpClient())                {                    if (!url.StartsWith("http", StringComparison.OrdinalIgnoreCase))                    {                         url = $"http://{url}";                    }                    using (var request = new HttpRequestMessage(method, url))                        {                        if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))                        {                            SetHttps();                        }                        var sc = new StreamContent(new MemoryStream());                        if (model != null)                        {                            var jsonStr = JsonConvert.SerializeObject(model);                            var bytes = Encoding.UTF8.GetBytes(jsonStr);                            sc = new StreamContent(new MemoryStream(bytes));                        }                        HeaderHandler(request, sc.Headers, "application/json", headers, cacheKey);                        request.Content = sc;                        var rsp = await client.SendAsync(request);                        return ResponseHandler(rsp);                    }                }            }            catch (Exception e)            {                _logger.LogError($"SendAsync {method.Method} 请求：{url}, 错误消息：{e.Message}, 请求参数：{JsonConvert.SerializeObject(model)}");                throw new Exception($"请求HTTP服务{new Uri(url).AbsolutePath}异常：{e.Message}");            }        }                /// 
        /// 发送HTTP表单请求        /// 
        /// HttpMethod.Post、HttpMethod.Put        /// 完整地址        /// 请求体对象        /// 鉴权请求头缓存key        /// 请求头        ///         public async Task SendFormAsync(HttpMethod method, string url, object model, string cacheKey = "", Dictionary headers = null)        {            _logger.LogInformation($"SendFormAsync {method.Method} url = {url}， cacheKey = {cacheKey}， data = {JsonConvert.SerializeObject(model)}");            try            {                var client = new RestClient();                var request = new RestRequest(url, Method.POST);                if (method == HttpMethod.Put)                {                    request.Method = Method.PUT;                }                                SetHeader(request, cacheKey, headers);                request.AlwaysMultipartFormData = true;                var props = model.GetType().GetProperties();                foreach (var item in props)                {                    var k = item.Name;                    var v = item.GetValue(model);                    if (v == null)                    {                        _logger.LogInformation($"SendFormAsync {method.Method} url = {url} {k} value is null");                        continue;                    }                    if (v.GetType().Name == "Dictionary`2") // 文件只支持字典类型                    {                        if (v is Dictionary)                         {                            var files = v as Dictionary;                            foreach (var obj in files) // 多个文件只能一个个添加，不能集合到List中                            {                                string ext = Path.GetExtension(obj.Key);                                ext = ext.RemovePreFix(".");                                _logger.LogInformation($"SendFormAsync file key = {k}, name = {obj.Key}, ext = {ext}, size = {obj.Value.Length}");                                request.AddFileBytes(k, obj.Value, obj.Key, $"image/{ext}");                            }                        }                    }                    else                    {                        request.AddParameter(k, v);                    }                }                var response = await client.ExecuteAsync(request);                if (response.StatusCode != HttpStatusCode.OK && response.StatusCode != HttpStatusCode.Created)                {                    _logger.LogError($"SendFormAsync {method.Method} {url} 响应失败: {response.Content}");                    throw new Exception($"服务器响应失败：status = {response.StatusCode}");                }                _logger.LogInformation($"SendFormAsync {method.Method} {url} Response: {response.Content}");                return JsonConvert.DeserializeObject(response.Content, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });            }            catch (Exception e)            {                _logger.LogError($"SendFormAsync {method.Method} 请求：{url}, 错误消息：{e.Message}, 请求参数：{JsonConvert.SerializeObject(model)}");                throw new Exception($"请求HTTP服务{new Uri(url).AbsolutePath}异常：{e.Message}");            }        }        /// 
        /// 设置请求头        /// 
        ///         ///         private void SetHeader(RestRequest request, string cacheKey, Dictionary headers)        {            // 鉴权请求头            var cacheHeaders = _cache.Get(cacheKey);            if (cacheHeaders != null)            {                foreach (var dic in cacheHeaders)                {                    _logger.LogInformation($"SetHeader cache header: {dic.Key} = {dic.Value}");                    if (dic.Key.Equals("authorization", StringComparison.OrdinalIgnoreCase))                    {                        request.AddHeader("Authorization", dic.Value);                    }                    else                    {                        request.AddHeader(dic.Key, dic.Value);                    }                }            }            // 默认请求头            if (headers != null && headers.Count > 0)            {                foreach (var dic in headers)                {                    request.AddHeader(dic.Key, dic.Value);                }            }        }        /// 
        /// 处理请求头        /// 
        /// new HttpRequestMessage        /// new MultipartFormDataContent        /// multipart/form-data        /// Dictionary        /// authorization        private void HeaderHandler(HttpRequestMessage request, HttpContentHeaders contentHeader, string contentType, Dictionary headers, string cacheKey)        {            // 添加默认请求头            if (headers != null && headers.ContainsKey("Content-Type"))            {                contentType = headers["Content-Type"];            }            if (string.IsNullOrEmpty(contentType))             {                contentType = "application/json"; // 默认application/json            }            _logger.LogInformation($"HeaderHandler {request.Method.Method} {request.RequestUri.AbsolutePath} default contentType header: {contentType}");            if (contentType.IndexOf("multipart/form-data") != -1)            {                contentHeader.Remove("Content-Type"); // MediaTypeHeaderValue不支持解析boundary，所以先删除再Add                contentHeader.TryAddWithoutValidation("Content-Type", contentType);            }            else            {                contentHeader.ContentType = new MediaTypeHeaderValue(contentType);             }            // 添加鉴权请求头            var cacheHeaders = _cache.Get(cacheKey);            if (cacheHeaders != null)            {                foreach (var dic in cacheHeaders)                {                    _logger.LogInformation($"HeaderHandler {request.Method.Method} {request.RequestUri.AbsolutePath} cache header: {dic.Key} = {dic.Value}");                    if (dic.Key.Equals("authorization", StringComparison.OrdinalIgnoreCase))                    {                        request.Headers.Authorization = new AuthenticationHeaderValue(dic.Value);                        // request.SetBearerToken(dic.Value); // 这个方法里加了前缀Bearer，针对接口不同                    }                    else                    {                        contentHeader.Add(dic.Key, dic.Value); // cookie、token ...                    }                }            }            // 添加参数请求头            if (headers != null && headers.Count > 0)            {                foreach (var dic in headers)                {                    if (contentHeader.ContentType.MediaType == dic.Value)                    {                        continue;                    }                    contentHeader.Add(dic.Key, dic.Value);                }            }        }        /// 
        /// 处理HTTP响应        /// 
        ///         ///         ///         ///         private T ResponseHandler(HttpResponseMessage rsp)        {            if (rsp.StatusCode != HttpStatusCode.OK && rsp.StatusCode != HttpStatusCode.Created)            {                _logger.LogError($"ResponseHandler {rsp.RequestMessage.Method.Method} {rsp.RequestMessage.RequestUri.AbsoluteUri} 响应失败: {rsp.Content.ReadAsStringAsync().Result}");                throw new Exception($"服务器响应失败：status = {rsp.StatusCode}");            }            if (rsp is T)            {               return (T)(object)rsp;  // 返回HttpResponseMessage，用于获取响应头            }            else            {                var json = rsp.Content.ReadAsStringAsync().Result;                _logger.LogInformation($"ResponseHandler {rsp.RequestMessage.Method.Method} {rsp.RequestMessage.RequestUri.AbsoluteUri} 响应：{json}");                return JsonConvert.DeserializeObject(json, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });                // return rsp.Content.ReadFromJsonAsync().Result; // 会检查int null类型报错            }        }        /// 
        /// 设置HTTPS        /// 
        private void SetHttps()        {            // set remote certificate Validation auto pass            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(RemoteCertificateValidate);            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls13 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;            // FIX：修复不同.Net版对一些SecurityProtocolType枚举支持情况不一致导致编译失败等问题，这里统一使用数值            //ServicePointManager.SecurityProtocol = (SecurityProtocolType)48 | (SecurityProtocolType)3072 | (SecurityProtocolType)768 | (SecurityProtocolType)192;        }        /// 
        /// 远程证书验证        /// 
        ///         ///         ///         ///         /// 验证是否通过，始终通过        private bool RemoteCertificateValidate(object sender, X509Certificate cert, X509Chain chain, SslPolicyErrors error)        {            return true;        }    }}

1、无法添加请求头content-type

var s = new HttpRequestMessage()s.Headers.Add("Content-Type", "")报错：Misused header name, "Content-Type". Make sure request headers are used with HttpRequestMessage,

var b = new HttpContentHeader()b.Add("Content-Type", "")报错：Cannot add value because header "Content-Type" does not support multiple values.

var b = new HttpContentHeader()b.ContentType = new MediaTypeHeaderValue("multipart/form-data; boundary=----8db27a5c21ea4f8");报错：The format of value "multipart/form-data; boundary=----8db27a5c21ea4f8" is invalid报错："multipart/form-data; ----8db27a507065123"is invalid报错："multipart/form-data; boundary=--8db27ca4cfafb57"is invalid

1、解决方案：

请看方法：HeaderHandler

关键词：