webapi推送消息html5,.Net WebApi消息拦截器之MessageHandler的示例

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 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 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 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();

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
The resource can be found at {0}.", 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 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);

}

}

}

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