Net Core中 使用Middleware 實現反向代理
- 2019 年 11 月 7 日
- 筆記
有這樣的一個需求，我們要攔截某些特定的請求，並將它們重新定向到另一台服務器中，然而客戶端並不知情。
在NetCore中我們可以用中間件來實現，
首先創建項目：
我這裡只有2.1 Version 的
添加ProxyMiddleware
ProxyMiddleware內容如下：
代碼不多有興趣的朋友可以調試一下。這裡還可以有很多的方向擴展。
public class ProxyMiddleware { private static readonly HttpClient _httpClient = new HttpClient(); private readonly RequestDelegate _nextRequestDelegate; private static readonly Uri _targetUri = new Uri("https://www.cnblogs.com/"); public ProxyMiddleware(RequestDelegate nextMiddleware) { _nextRequestDelegate = nextMiddleware; } public async Task Invoke(HttpContext context) { bool validateUri = false; if (context.Request.Path.StartsWithSegments("/api/values", out var Path)) { validateUri = true; } if (validateUri == true) { var targetRequestMessage = CreateTargetMessage(context); using (var responseMessage = await _httpClient.SendAsync(targetRequestMessage)) { context.Response.StatusCode = (int)responseMessage.StatusCode; CloneResponseHeadersIntoContext(context, responseMessage); await responseMessage.Content.CopyToAsync(context.Response.Body); } return; } await _nextRequestDelegate(context); } private void CloneRequestContentAndHeaders(HttpContext context, HttpRequestMessage requestMessage) { foreach (var header in context.Request.Headers) { requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray()); } } private HttpRequestMessage CreateTargetMessage(HttpContext context) { var requestMessage = new HttpRequestMessage(); CloneRequestContentAndHeaders(context, requestMessage); requestMessage.RequestUri = _targetUri; requestMessage.Headers.Host = _targetUri.Host; requestMessage.Method = new HttpMethod(context.Request.Method); return requestMessage; } private void CloneResponseHeadersIntoContext(HttpContext context, HttpResponseMessage responseMessage) { foreach (var header in responseMessage.Headers) { context.Response.Headers[header.Key] = header.Value.ToArray(); } foreach (var header in responseMessage.Content.Headers) { context.Response.Headers[header.Key] = header.Value.ToArray(); } context.Response.Headers.Remove("Transfer-Encoding"); } }
添加管道
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } app.UseMiddleware<ProxyMiddleware>(); app.UseMvc(); }
運行結果：
大家可以注意瀏覽器網址，以及顯示的內容就可以了，（樣式沒了）
代碼解釋：
所有的描述在代碼中，這裡我只是標出這點代碼的重點
創建靜態HttpClient連接，減少連接池數量
private static readonly HttpClient _httpClient = new HttpClient();
private readonly RequestDelegate _nextRequestDelegate;
新的目標服務器 private static readonly Uri _targetUri = new Uri("https://www.cnblogs.com/"); public ProxyMiddleware(RequestDelegate nextMiddleware) { _nextRequestDelegate = nextMiddleware; }
所有的工作將由 Invoke執行
public async Task Invoke(HttpContext context) { bool validateUri = false; if (context.Request.Path.StartsWithSegments("/api/values", out var Path)) { validateUri = true; } if (validateUri == true) { var targetRequestMessage = CreateTargetMessage(context); using (var responseMessage = await _httpClient.SendAsync(targetRequestMessage)) { context.Response.StatusCode = (int)responseMessage.StatusCode; CloneResponseHeadersIntoContext(context, responseMessage); await responseMessage.Content.CopyToAsync(context.Response.Body); } return; } await _nextRequestDelegate(context); }
private void CloneResponseHeadersIntoContext(HttpContext context, HttpResponseMessage responseMessage) { foreach (var header in responseMessage.Headers) { context.Response.Headers[header.Key] = header.Value.ToArray(); } foreach (var header in responseMessage.Content.Headers) { context.Response.Headers[header.Key] = header.Value.ToArray(); }
這裡有一個坑大家注意了，有興趣的同學可以調查研究一下，要是介紹的話可以單獨開一篇了 context.Response.Headers.Remove("Transfer-Encoding"); }
有不足之處 希望大家指出相互學習。
