实现的原理比较直接，定义一个MessageHandler记录WebAPI的请求记录，然后将这些请求日志推送到客户端，客户端就是一个查看日志的页面，实时将请求日志展示在页面中。
这个例子的目的是演示如何在PersistentConnection类外部给Clients推送消息
实现过程
一、服务端
服务端同时具备SignalR和WebAPI的功能，通过定义一个记录日志的MessageHandler实现对WebAPI请求的拦截，并生成请求记录，然后推送到客户端
step 1
创建一个具备WebAPI功能的站点，为了简化起见，设置Authentication为No Authentication
step 2
创建一个DelegatingHandler，用于记录WebAPI日志，代码如下
下面代码没有涉及到SignalR的功能，日志展示是通过ILoggingDisplay接口传入
public class LoggingHandler : DelegatingHandler
{
private static readonly string _loggingInfoKey = "loggingInfo"; private ILoggingDisplay _loggingDisplay; public LoggingHandler(ILoggingDisplay loggingDisplay)
{
_loggingDisplay = loggingDisplay;
} public LoggingHandler(HttpMessageHandler innerHandler, ILoggingDisplay loggingDisplay)
: base(innerHandler)
{
_loggingDisplay = loggingDisplay;
} protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
LogRequestLoggingInfo(request);
return base.SendAsync(request, cancellationToken).ContinueWith(task =>
{
var response = task.Result;
LogResponseLoggingInfo(response);
return response;
});
} private void LogRequestLoggingInfo(HttpRequestMessage request)
{
var info = new ApiLoggingInfo();
info.HttpMethod = request.Method.Method;
info.UriAccessed = request.RequestUri.AbsoluteUri;
info.IpAddress = HttpContext.Current != null ? HttpContext.Current.Request.UserHostAddress : "0.0.0.0";
info.StartTime = DateTime.Now;
ExtractMessageHeadersIntoLoggingInfo(info, request.Headers.ToList());
request.Properties.Add(_loggingInfoKey, info);
} private void LogResponseLoggingInfo(HttpResponseMessage response)
{
object loggingInfoObject = null;
if (!response.RequestMessage.Properties.TryGetValue(_loggingInfoKey, out loggingInfoObject))
{
return;
}
var info = loggingInfoObject as ApiLoggingInfo;
if (info == null)
{
return;
}
info.HttpMethod = response.RequestMessage.Method.ToString();
info.ResponseStatusCode = response.StatusCode;
info.ResponseStatusMessage = response.ReasonPhrase;
info.UriAccessed = response.RequestMessage.RequestUri.AbsoluteUri;
info.IpAddress = HttpContext.Current != null ? HttpContext.Current.Request.UserHostAddress : "0.0.0.0";
info.EndTime = DateTime.Now;
info.TotalTime = (info.EndTime - info.StartTime).TotalMilliseconds;
_loggingDisplay.Display(info);
} private void ExtractMessageHeadersIntoLoggingInfo(ApiLoggingInfo info, List<KeyValuePair<string, IEnumerable<string>>> headers)
{
headers.ForEach(h =>
{
var headerValues = new StringBuilder(); if (h.Value != null)
{
foreach (var hv in h.Value)
{
if (headerValues.Length > )
{
headerValues.Append(", ");
}
headerValues.Append(hv);
}
}
info.Headers.Add(string.Format("{0}: {1}", h.Key, headerValues.ToString()));
});
}
}
LoggingHandler
step 3
引入SignalR相关packages
Install-Package Microsoft.AspNet.SignalR
新建一个PersistentConnection，代码为空即可（因为不涉及到客户端调用，推送也是在类的外部执行）
public class RequestMonitor : PersistentConnection
{
}
添加一个Startup类
public void Configuration(IAppBuilder app)
{
app.MapSignalR<RequestMonitor>("/monitor");
}
step 4
创建一个类实现ILoggingDisplay接口，用SignalR推送的方式实现这个接口
代码比较关键的部分就是通过GlobalHost.ConnectionManager获取当前应用程序的connectionContext,得到这个context就可以类似在PersistentConnection内部给clients推送消息
public class SignalRLoggingDisplay : ILoggingDisplay
{
/// <summary>
/// PersistentConnection上下文
/// </summary>
private static IPersistentConnectionContext connectionContext = GlobalHost.ConnectionManager.GetConnectionContext<RequestMonitor>(); public void Display(ApiLoggingInfo loggingInfo)
{
var message = new StringBuilder();
message.AppendFormat("StartTime:{0},Method:{1},Url:{2},ReponseStatus:{3},TotalTime:{4}"
, loggingInfo.StartTime, loggingInfo.HttpMethod, loggingInfo.UriAccessed, loggingInfo.ResponseStatusCode, loggingInfo.TotalTime);
message.AppendLine();
message.AppendFormat("Headers:{0},Body:{1}", string.Join(",", loggingInfo.Headers), loggingInfo.BodyContent);
connectionContext.Connection.Broadcast(message.ToString());
}
SignalRLoggingDisplay
step 5
在WebApiConfig的Register方法中添加自定义的handler
public static void Register(HttpConfiguration config)
{
config.MapHttpAttributeRoutes(); config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
); config.MessageHandlers.Add(new LoggingHandler(new SignalRLoggingDisplay()));
}
RegisterHandler
到此完成服务端的功能实现
二、客户端
客户端只需要一个监控页面，html页面足矣，其主要功能是提供开始监控、停止监控功能，其他都是接收服务端的推送并展示功能代码。
<!DOCTYPE html>
<html>
<head>
<title>Web API页面实时请求监控</title>
<meta charset="utf-8" />
</head>
<body>
<h1>Web API Request Logs</h1>
<div>
<input type="button" value="start" id="btnStart"/>
<input type="button" value="stop" id="btnStop"/>
<input type="button" value="clear" id="btnClear"/>
</div>
<ul id="requests"></ul>
<script src="/Scripts/jquery-1.10.2.min.js"></script>
<script src="/Scripts/jquery.signalR-2.2.0.min.js"></script>
<script>
$(function () {
var requests = $("#requests");
var startButton = $("#btnStart");
var stopButton = $("#btnStop");
var connection = null; enable(stopButton, false);
enable(startButton, true); startButton.click(function () {
startConnection();
enable(stopButton, true);
enable(startButton, false);
}); $("#btnClear").click(function () {
$("#requests").children().remove();
}); stopButton.click(function () {
stopConnection();
enable(stopButton, false);
enable(startButton, true);
}); function startConnection() {
stopConnection();
connection = $.connection("/monitor");
connection.start()
.fail(function () {
console.log("connect failed");
});
connection.received(function (data) {
data = data.replace(/\r\n/g, "<br/>")
data = data.replace(/\n/g, "<br/>");
requests.append("<li>" + data + "</li>");
});
} function stopConnection() {
if (connection != null){
connection.stop();
}
} function enable(button, enabled) {
if (enabled) {
button.removeAttr("disabled");
}
else {
button.attr("disabled", "disabled");
}
}
});
</script>
</body>
</html>
Monitor
示例代码下载