DotNet WebApi消息拦截器之MessageHandler
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
image
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=\"{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);
}
}
}
