Net Core中 使用Middleware 实现反向代理

  • 2019 年 11 月 7 日
  • 筆記

有这样的一个需求，我们要拦截某些特定的请求，并将它们重新定向到另一台服务器中，然而客户端并不知情。

在NetCore中我们可以用中间件来实现，

首先创建项目：

　　我这里只有2.1 Version 的

　　

添加ProxyMiddleware

　　

 

ProxyMiddleware内容如下：

 　　代码不多有兴趣的朋友可以调试一下。这里还可以有很多的方向扩展。

 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();          }

运行结果：

　　大家可以注意浏览器网址，以及显示的内容就可以了，（样式没了）

　　

 

 

 代码解释：

　　所有的描述在代码中，这里我只是标出这点代码的重点

        创建静态HttpClient连接，减少连接池数量
　　　　 private static readonly HttpClient _httpClient = new HttpClient();
　　　　　　          private readonly RequestDelegate _nextRequestDelegate;
　　　　　新的目标服务器          private static readonly Uri _targetUri = new Uri("https://www.cnblogs.com/");          public ProxyMiddleware(RequestDelegate nextMiddleware)          {              _nextRequestDelegate = nextMiddleware;          }

        
　　　　　所有的工作将由 Invoke执行 
　　　　　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();              }
　　　　　　　这里有一个坑大家注意了，有兴趣的同学可以调查研究一下，要是介绍的话可以单独开一篇了              context.Response.Headers.Remove("Transfer-Encoding");          }

 

有不足之处 希望大家指出相互学习。

        

 

 

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