消息拦截器是一个类，接收 HTTP request并返回 HTTP response,Message handler 继承自抽象类 HttpMessageHandler
可以自定义 MessageHandler,消息拦截器的作用如:
读取或更改请求头 request headers
添加 response headers
在到达 controller 之前，进行参数验证
自定义 Message Handlers
自定义 MessageHandler 需要继承 System.Net.Http.DelegatingHander 并且重载SendAsync方法
Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken cancellationToken);
这个方法的一般的处理流程是
处理请求信息
调用 base.SendAsync 方法，吧请求发送给内部处理
内部处理完成之后，返回 response message(这个过程是异步的)
处理 response 之后，返回给调用者
public class MessageHandler1 : DelegatingHandler { protected async override Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken cancellationToken) { Debug.WriteLine("Process request"); // Call the inner handler. var response = await base.SendAsync(request, cancellationToken); Debug.WriteLine("Process response"); return response; } }
消息拦截器生效
在 WebApiConfig中注册相关
public static class WebApiConfig { public static void Register(HttpConfiguration config) { config.MessageHandlers.Add(new MessageHandler1()); config.MessageHandlers.Add(new MessageHandler2()); // Other code not shown... } }
https 请求拦截器
要求所有的请求都必须是https的请求，可以自定义一个https的拦截器，如果是https请求，就继续处理，否则就返回相关的提示信息
public class RequireHttpsHandler : DelegatingHandler { public RequireHttpsHandler(int httpsPort) { _httpsPort = httpsPort; } public RequireHttpsHandler() : this(443) { } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { //判断是否是 https 请求 if (request.RequestUri.Scheme == Uri.UriSchemeHttps) return base.SendAsync(request, cancellationToken); var response = CreateResponse(request); var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } private HttpResponseMessage CreateResponse(HttpRequestMessage request) { HttpResponseMessage response; var uri = new UriBuilder(request.RequestUri); uri.Scheme = Uri.UriSchemeHttps; uri.Port = _httpsPort; var body = string.Format("HTTPS is required<br/>The resource can be found at <a href=https://www.jb51.net/article/\"{0}\">{0}</a>.", uri.Uri.AbsoluteUri); if (request.Method.Equals(HttpMethod.Get) || request.Method.Equals(HttpMethod.Head)) { response = request.CreateResponse(HttpStatusCode.Found); response.Headers.Location = uri.Uri; if (request.Method.Equals(HttpMethod.Get)) response.Content = new StringContent(body, Encoding.UTF8, "text/html"); } else { response = request.CreateResponse(HttpStatusCode.NotFound); response.Content = new StringContent(body, Encoding.UTF8, "text/html"); } return response; } }
Enable CORS 拦截器
public class SimpleCorsHandler : DelegatingHandler { private const string origin = "Origin"; private const string accessControlRequestMethod = "Access-Control-Request-Method"; private const string accessControlRequestHeaders = "Access-Control-Request-Headers"; private const string accessControlAllowOrigin = "Access-Control-Allow-Origin"; private const string accessControlAllowMethods = "Access-Control-Allow-Methods"; private const string accessControlAllowHeaders = "Access-Control-Allow-Headers"; protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var isCorsRequest = request.Headers.Contains(origin); var isPreflightRequest = request.Method == HttpMethod.Options; if (isCorsRequest) { if (isPreflightRequest) { return Task.Factory.StartNew(() => { var response = new HttpResponseMessage(HttpStatusCode.OK); response.Headers.Add(accessControlAllowOrigin, request.Headers.GetValues(origin).First()); var currentAccessControlRequestMethod = request.Headers.GetValues(accessControlRequestMethod). FirstOrDefault(); if (currentAccessControlRequestMethod != null) { response.Headers.Add(accessControlAllowMethods, currentAccessControlRequestMethod); } var requestedHeaders = string.Join(", ", request.Headers.GetValues(accessControlRequestHeaders)); if (!string.IsNullOrEmpty(requestedHeaders)) { response.Headers.Add(accessControlAllowHeaders, requestedHeaders); } return response; }, cancellationToken); } else { return base.SendAsync(request, cancellationToken).ContinueWith(t => { var resp = t.Result; resp.Headers.Add( accessControlAllowOrigin, request.Headers.GetValues(origin).First()); return resp; }); } } else { return base.SendAsync(request, cancellationToken); } } }