C# 关于HttpClient的使用

当我们在C#中调用RestApi通常有三种方式

HttpWebRequest	是一种相对底层的处理 Http request/response 的方式	已过时
WebClient	提供了对 HttpWebRequest 的高层封装，来简化使用者的调用	已过时
HttpClient	是一种新的处理 Http request/response 工具包，具有更高的性能	推荐使用

为什么推荐使用HttpClient

WebRequest

.NET Framework 中第一个用来处理 Http 请求的类，非常灵活。可以用来存取 headers, cookies, protocols 和 timeouts 等等。但灵活的同时也导致使用难度加大，各个开发都有自己的写法。

HttpWebRequest http =  (HttpWebRequest)WebRequest.Create("http://localhost:8081/api/default");
WebResponse response = http.GetResponse();
Stream memoryStream = response.GetResponseStream();
StreamReader streamReader = new StreamReader(memoryStream);
string data = streamReader.ReadToEnd();

WebClient

基于HttpWebRequest的封装,提供了使用便利性,但舍弃了部分性能。在只做简单api调用时优势很大。不太适用bgy各系统之间调用的千奇百怪鉴权。

using (var webClient = new WebClient()) { 
    var data = webClient.DownloadString("http://localhost:8081/api/default"); 
}

HttpClient

HttpClient 作为后来之物，它吸取了 HttpWebRequest 的灵活性及 WebClient 的便捷性，所以说 🐟 和 🐻 可兼得。

//单例注入HttpClient client
HttpResponseMessage response = await client.GetAsync(uri);
if (response.IsSuccessStatusCode)
{
    var data = await response.Content.ReadAsStringAsync();
}

---

基于bgy接口调用行情的HttpClient封装

url	请求地址	鉴于get请求,参数都直接拼接在url后面
data	json字符串	多数都是json交互,少量会有Form
headers	请求头	多数对接都是请求头附加token用于网关鉴权，使用字典类型声明方便快捷
contentType	请求类型	默认json，可选Form
tryCount	重试次数	目前是即时重试，后续可拓展EventBus做延迟重试功能
writeLog	是否写日志	建议接口调用都保留日志，避免甩锅🤷‍

Get请求

private async Task<string> GetHandle(string url, Dictionary<string, string> headers = null, int tryCount = 0, bool writeLog = true)
{
	HttpRequestMessage message = new HttpRequestMessage(System.Net.Http.HttpMethod.Get, url);
	if (headers?.ContainsKey("Authorization") == true)
	{
		headers.TryGetValue("Authorization", out string val);
		headers.Remove("Authorization");
		message.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", val);
	}
	if (message.Content != null)
		message.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(JsonDataType);
	headers?.ForEach(item =>
	{
		message.Headers.Add(item.Key, item.Value);
	});
	if (writeLog)
	{
		var apiLog = new SystemApiLog
		{
			RequestUrl = message.RequestUri.AbsoluteUri
		};
		DateTime dtSpan = DateTime.Now;
		apiLog.Method = "HttpGet";
		apiLog.ResponseIp = localIp;
		apiLog.ApiPath = GetApiPath();
		try
		{
			var result = await SendAsync(message);
			var html = await result.Content.ReadAsStringAsync();
			apiLog.ResponseData = html;
			apiLog.ElapsedTime = (DateTime.Now - dtSpan).TotalSeconds;
			BusHelper.ApiLog(apiLog);
			return html;
		}
		catch (Exception ex)
		{
			apiLog.ResponseData = ex.ToString();
			apiLog.ElapsedTime = (DateTime.Now - dtSpan).TotalSeconds;
			BusHelper.ApiLog(apiLog); //写日志换成自己的表！
			if (tryCount > 0)
				return await GetHandle(url, headers, --tryCount);
			return null;
		}
	}
	else
	{
		var result = await SendAsync(message);
		var html = await result.Content.ReadAsStringAsync();
		return html;
	}
}

Post请求

private async Task<string> PostHandle(string url, string data, Dictionary<string, string> headers = null, ContentType contentType = ContentType.Json, int tryCount = 0, bool writeLog = true)
{
	HttpRequestMessage message = new HttpRequestMessage(System.Net.Http.HttpMethod.Post, url)
	{
		Content = new StringContent(data, Encoding.UTF8)
	};
	if (headers?.ContainsKey("Authorization") == true)
	{
		headers.TryGetValue("Authorization", out string val);
		headers.Remove("Authorization");
		message.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", val);
	}
	message.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(contentType == ContentType.Form ? FromDataType : JsonDataType);
	headers?.ForEach(item =>
	{
		message.Headers.Add(item.Key, item.Value);
	});
	//请求日志
	if (writeLog)
	{
		var apiLog = new SystemApiLog
		{
			RequestUrl = message.RequestUri.AbsoluteUri
		};
		DateTime dtSpan = DateTime.Now;
		apiLog.Method = "HttpPost";
		apiLog.ResponseIp = localIp;
		apiLog.RequestData = data;
		apiLog.ApiPath = GetApiPath();
		try
		{
			var result = await SendAsync(message);
			var html = await result.Content.ReadAsStringAsync();
			apiLog.ResponseData = html;
			apiLog.ElapsedTime = (DateTime.Now - dtSpan).TotalSeconds;
			BusHelper.ApiLog(apiLog);//写日志换成自己的表！
			return html;
		}
		//异常重试及异常日志
		catch (Exception ex)
		{
			apiLog.ResponseData = ex.ToString();
			apiLog.ElapsedTime = (DateTime.Now - dtSpan).TotalSeconds;
			BusHelper.ApiLog(apiLog);
			if (tryCount > 0)
				return await PostHandle(url, data, headers, contentType, --tryCount);
			return null;
		}
	}
	else
	{
		var result = await SendAsync(message);
		var html = await result.Content.ReadAsStringAsync();
		return html;
	}
}

依赖的常量or方法

private const string FromDataType = "application/x-www-form-urlencoded";
private const string JsonDataType = "application/json";
private static readonly string localIp = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces()
                .Select(p => p.GetIPProperties())
                .SelectMany(p => p.UnicastAddresses) 
                .FirstOrDefault(p => p.Address.AddressFamily == AddressFamily.InterNetwork && !IPAddress.IsLoopback(p.Address))?.Address.ToString();

/// <summary>
/// 反射请求方法获取apipath
/// </summary>
private string GetApiPath()
{
	try
	{
		var st = new StackTrace(true);
		//index:0为本身的方法；1为调用方法；2为其上上层，依次类推
		MethodBase mb = st.GetFrame(4).GetMethod();
		mb = NewMethod(st, mb, 4);
		return $"{mb.Name}";
	}
	catch (Exception)
	{
		//catch 避免因反射层数不够导致的异常 影响接口请求
		return null;
	}
	static MethodBase NewMethod(StackTrace st, MethodBase mb, int index)
	{
		if (mb.DeclaringType.Name == nameof(HttpApi) || mb.DeclaringType.Name == "AsyncMethodBuilderCore")
		{
			mb = st.GetFrame(index + 1).GetMethod();
			return NewMethod(st, mb, index + 1);
		}
		return mb;
	}
}