Net Core中 使用Middleware 实现反向代理

有这样的一个需求，咱们要拦截某些特定的请求，并将它们从新定向到另外一台服务器中，然而客户端并不知情。

在NetCore中咱们能够用中间件来实现，

首先建立项目：

　　我这里只有2.1 Version 的

　　

添加ProxyMiddleware

　　

 

ProxyMiddleware内容以下：

 　　代码很少有兴趣的朋友能够调试一下。这里还能够有不少的方向扩展。

 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：

　　你们能够注意浏览器网址，以及显示的内容就能够了，（样式没了）

　　

 

 

 代码解释：

　　全部的描述在代码中，这里我只是标出这点代码的重点

        建立静态HttpClient链接，减小链接池数量
　　　　 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;
        }

        
　　　　　全部的工做将由 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();
            }
　　　　　　　这里有一个坑你们注意了，有兴趣的同窗能够调查研究一下，要是介绍的话能够单独开一篇了
            context.Response.Headers.Remove("Transfer-Encoding");
        }

 

有不足之处 但愿你们指出相互学习。