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
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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
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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
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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
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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="{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
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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); } } } |
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。
原文链接:https://www.jianshu.com/p/a38487f9b692