上一篇了解到 请求到达服务器后是怎么被IIS处理的，本篇来看一下在ISAPI内部是怎么处理请求的；
首先ISAPI 有三个重量级入口：
一， ISAPIRuntimeRequest.ProcessRequest() 最外层入口
- 根据句柄ecb创建HttpWorkerRequest 对象封装原始请求报文 wr ；
public int ProcessRequest(IntPtr ecb, int iWRType)
{
......
ISAPIWorkerRequest wr = null;
try
{
bool useOOP = iWRType == 1;
wr = ISAPIWorkerRequest.CreateWorkerRequest(ecb, useOOP);
wr.Initialize();
string appPathTranslated = wr.GetAppPathTranslated();
string appDomainAppPathInternal = HttpRuntime.AppDomainAppPathInternal;
if ((appDomainAppPathInternal == null) || StringUtil.EqualsIgnoreCase(appPathTranslated, appDomainAppPathInternal))
{
HttpRuntime.ProcessRequestNoDemand(wr);
return 0;
}
......
1.1. 根据IIS版本来创建请求报文 ISAPIWorkerRequest
internal static ISAPIWorkerRequest CreateWorkerRequest(IntPtr ecb, bool useOOP)
{
......
if (num >= 7)
{
EtwTrace.TraceEnableCheck(EtwTraceConfigType.IIS7_ISAPI, ecb);
}
else
{
EtwTrace.TraceEnableCheck(EtwTraceConfigType.DOWNLEVEL, IntPtr.Zero);
}
if (EtwTrace.IsTraceEnabled(5, 1))
{
EtwTrace.Trace(EtwTraceType.ETW_TYPE_APPDOMAIN_ENTER, ecb, Thread.GetDomain().FriendlyName, null, true);
}
if (num >= 7)
{
return new ISAPIWorkerRequestInProcForIIS7(ecb);
}
if (num == 6)
{
return new ISAPIWorkerRequestInProcForIIS6(ecb);
}
return new ISAPIWorkerRequestInProc(ecb);
}
二， HttpRuntime.ProcessRequestInternal()
1.根据HttpRuntime.ProcessRequestNoDemand(wr);方法内部创建HttpContext，HttpApplication对象；
internal static void ProcessRequestNoDemand(HttpWorkerRequest wr)
{
RequestQueue queue = _theRuntime(HttpRuntime实例)._requestQueue(请求队列);
wr.UpdateInitialCounters();
if (queue != null)
{
wr = queue.GetRequestToExecute(wr);
}
if (wr != null)
{
CalculateWaitTimeAndUpdatePerfCounter(wr);
wr.ResetStartTime();
ProcessRequestNow(wr);
}
}
2.我们接着进入ProcessRequestNow(wr) 方法，方法根据请求报文开始创建HttpContext对象；
private void ProcessRequestInternal(HttpWorkerRequest wr)
{
......
HttpContext context;
try
{
context = new HttpContext(wr, false);
2.1. 这是实例HttpContext的方法，我们看到内部实例了常用对象 HttpRequest和HttpResponse
internal HttpContext(HttpWorkerRequest wr, bool initResponseWriter)
{
this._timeoutStartTimeUtcTicks = -1L;
this._timeoutTicks = -1L;
this._threadAbortOnTimeout = true;
this.ThreadContextId = new object();
this._wr = wr;
this.Init(new HttpRequest(wr, this), new HttpResponse(wr, this));
if (initResponseWriter)
{
this._response.InitResponseWriter();
}
PerfCounters.IncrementCounter(AppPerfCounter.REQUESTS_EXECUTING);
}
- 我们接下来看 HttpApplicationFactory.GetApplicationInstance(context) 方法内部通过维护一个应用程序池，当不存在时 实例化了HttpApplication(通过反射 Global.asax 文件)；我们在这里发现原来IHttpHandler 是HttpApplication 的基类；
private void ProcessRequestInternal(HttpWorkerRequest wr)
......
context.Response.InitResponseWriter();
IHttpHandler applicationInstance = HttpApplicationFactory.GetApplicationInstance(context);
......
}
}
三. HttpApplication.Init() 管道事件
以上说了那么多废话，因为我们什么也改不了，只是对请求流程有个大致的了解；
下面我们就可以 跟微软达达互动了 (*￣︶￣)
1.我们还是从 HttpApplication创建过程来看，我们注意到有一个InitInternal初始实例方法，在此方法中有两个 InitModules(),BuildSteps()方法；
private HttpApplication GetNormalApplicationInstance(HttpContext context)
{
HttpApplication state = null;
......
if (state == null)
{
state = (HttpApplication) HttpRuntime.CreateNonPublicInstance(this._theApplicationType);
using (new ApplicationImpersonationContext())
{
state.InitInternal(context, this._state, this._eventHandlerMethods);
}
}
......
2.在 InitModules方法中，通过读取Web.Config配置文件关于HttpModule信息，并加入集合；最后通过方法InitModulesCommon()遍历执行每个模块的初始化方法 Init();
private void InitModules()
{
HttpModuleCollection modules = RuntimeConfig.GetAppConfig().HttpModules.CreateModules();
HttpModuleCollection other = this.CreateDynamicModules();
modules.AppendCollection(other);
this._moduleCollection = modules;
this.InitModulesCommon();
}
3.在BuildSteps()方法中注册了管道事件，F12发现此方法是抽象方法，全局搜索找到； 方法结束时有一个CopyTo 方法，这个是把所有事件按顺序储存；
internal override void BuildSteps(WaitCallback stepCallback)
{
ArrayList steps = new ArrayList();
HttpApplication app = base._application;
bool flag = false;
UrlMappingsSection urlMappings = RuntimeConfig.GetConfig().UrlMappings;
flag = urlMappings.IsEnabled && (urlMappings.UrlMappings.Count > 0);
steps.Add(new HttpApplication.ValidateRequestExecutionStep(app));
steps.Add(new HttpApplication.ValidatePathExecutionStep(app));
if (flag)
{
steps.Add(new HttpApplication.UrlMappingsExecutionStep(app));
}
// 管道事件
app.CreateEventExecutionSteps(HttpApplication.EventBeginRequest, steps);
app.CreateEventExecutionSteps(HttpApplication.EventAuthenticateRequest, steps);
app.CreateEventExecutionSteps(HttpApplication.EventDefaultAuthentication, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostAuthenticateRequest, steps);
app.CreateEventExecutionSteps(HttpApplication.EventAuthorizeRequest, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostAuthorizeRequest, steps);
app.CreateEventExecutionSteps(HttpApplication.EventResolveRequestCache, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostResolveRequestCache, steps);
steps.Add(new HttpApplication.MapHandlerExecutionStep(app));
app.CreateEventExecutionSteps(HttpApplication.EventPostMapRequestHandler, steps);
app.CreateEventExecutionSteps(HttpApplication.EventAcquireRequestState, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostAcquireRequestState, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPreRequestHandlerExecute, steps);
steps.Add(app.CreateImplicitAsyncPreloadExecutionStep());
steps.Add(new HttpApplication.CallHandlerExecutionStep(app));
app.CreateEventExecutionSteps(HttpApplication.EventPostRequestHandlerExecute, steps);
app.CreateEventExecutionSteps(HttpApplication.EventReleaseRequestState, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostReleaseRequestState, steps);
steps.Add(new HttpApplication.CallFilterExecutionStep(app));
app.CreateEventExecutionSteps(HttpApplication.EventUpdateRequestCache, steps);
app.CreateEventExecutionSteps(HttpApplication.EventPostUpdateRequestCache, steps);
this._endRequestStepIndex = steps.Count;
app.CreateEventExecutionSteps(HttpApplication.EventEndRequest, steps);
steps.Add(new HttpApplication.NoopExecutionStep());
this._execSteps = new HttpApplication.IExecutionStep[steps.Count];
steps.CopyTo(this._execSteps);
this._resumeStepsWaitCallback = stepCallback;
}
4.我们依然回到ProcessRequestInternal方法中,执行BeginProcessRequest方法触发每个事件执行；
if (applicationInstance is IHttpAsyncHandler)
{
IHttpAsyncHandler handler2 = (IHttpAsyncHandler) applicationInstance;
context.AsyncAppHandler = handler2;
handler2.BeginProcessRequest(context, this._handlerCompletionCallback, context);
}
四，模块和事件 ——管道
管道事件[http://www.cnblogs.com/edisonchou/p/4201855.html]
image.png
模块 IHttpmodule ,事件 IHttpHandler. 两种同属于请求处理注入逻辑，不同点在于 模块 针对于全部请求 逻辑注入，事件针对于指定文件 逻辑注入；
1.通过在<modules>节点下 配置模块，通过在 <handlers>节点下 配置事件,我们从它们配置项也可以看出来区别；
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<!--<modules runAllManagedModulesForAllRequests="true" />-->
<modules>
<add name="CustomeModule" type="MVC3.CustomeModule, MVC3" />
</modules>
<handlers>
<add name="CustomeHandler" verb="*" path="*.txt" type="MVC3.CustomeHandler, MVC3"/>
</handlers>
</system.webServer>
- 实现相应的接口； 注意实现IHttpModule接口时Dispose方法的实现和IHttpHandler接口属性IsReusable 改为return true；
public class CustomeModule : IHttpModule
{
public void Dispose()
{
throw new NotImplementedException();
}
public void Init(HttpApplication context)
{
//context.Context.Response.Write("Module");
context.BeginRequest += context_BeginRequest;
context.PreRequestHandlerExecute += context_PreRequestHandlerExecute;
context.PostRequestHandlerExecute += context_PostRequestHandlerExecute;
}
void context_PostRequestHandlerExecute(object sender, EventArgs e)
{
((HttpApplication)sender).Context.Response.Write("PostRequestHandlerExecute <br> ");
}
void context_PreRequestHandlerExecute(object sender, EventArgs e)
{
((HttpApplication)sender).Context.Response.Write("PreRequestHandlerExecute <br> ");
}
void context_BeginRequest(object sender, EventArgs e)
{
((HttpApplication)sender).Context.Response.Write("BeginRequest <br> ");
}
}
public class CustomeHandler : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.Write("CustomeHandler <br>");
}
public bool IsReusable
{
get { return true; }
}
}
3.我们看页面执行结果，和管道事件的执行顺序是一致的
jpg
- 总结 常用思路：
httphandler 可以运用在图片盗链上等等；httpmodule 可以用在权限等等；
参考文档 有直接使用博友的图，在此对以下博友表示感谢：
博客园[http://www.cnblogs.com/edisonchou/p/4195259.html]
博客园[http://www.cnblogs.com/edisonchou/p/4201855.html]
博客园[http://www.cnblogs.com/OceanHeaven/p/6514230.html]
博客园[https://www.cnblogs.com/Rayblog/p/6394315.html]
博客园[https://www.cnblogs.com/fish-li/archive/2013/01/04/2844908.html]
biancheng[http://www.bianceng.cn/Programming/net/201210/34557_3.htm]
MSDN iis与asp.net流程[https://msdn.microsoft.com/zh-cn/library/bb470252(v=vs.100).aspx]
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