写在前面
关于IHttpModule的相关内容，在面试的时候也被问到过，当时也是隐隐约约的感觉这个接口有一个Init方法，可以在实现类中的Init方法注册一系列的事件，说句实话，具体哪些事件，忘了差不多了。今天周末在家，也确实没什么事，就算是对这块知识进行查漏补缺了。
IHttpModule工作方式
熟悉asp.net生命周期的朋友，应该知道HttpModule的执行是在HttpHandler之前被执行，执行HttpModule的一系列事件后然后执行HttpHandler，然后又执行HttpModule的一些事件。具体的可以参考下面的生命周期的图。
而HttpHandler才是处理http请求的地方，HttpModule是一个HTTP请求的“必经之路”，所以可以在这个HTTP请求传递到真正的请求处理中心（HttpHandler）之前附加一些需要的信息在这个HTTP请求信息之上，或者针对截获的这个HTTP请求信息作一些额外的工作，或者在某些情况下干脆终止满足一些条件的HTTP请求，从而可以起到一个Filter过滤器的作用。
一个HTTP请求在HttpModule容器的传递过程中，会在某一时刻（ResolveRequestCache事件）将这个HTTP请求传递给HttpHandler容器。在这个事件之后，HttpModule容器会建立一个HttpHandler的入口实例，但是此时并没有将HTTP请求控制权交出，而是继续触发AcquireRequestState事件以及PreRequestHandlerExcute事件。在PreRequestHandlerExcute事件之后，HttpModule窗口就会将控制权暂时交给HttpHandler容器，以便进行真正的HTTP请求处理工作。
而在HttpHandler容器内部会执行ProcessRequest方法来处理HTTP请求。在容器HttpHandler处理完毕整个HTTP请求之后，会将控制权交还给HttpModule，HttpModule则会继续对处理完毕的HTTP请求信息流进行层层的转交动作，直到返回到客户端为止。
一个实例
项目结构
MyHttpModule代码
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Web;
5
6 namespace MyHttpModule
7 {
8 /// <summary>
9 /// 自定义HttpModule
10 /// </summary>
11 public class MyHttpModule : IHttpModule
12 {
13 public void Dispose()
14 {
15 throw new NotImplementedException();
16 }
17
18 public void Init(HttpApplication context)
19 {
20 context.BeginRequest += context_BeginRequest;
21 context.EndRequest += context_EndRequest;
22 }
23
24 void context_EndRequest(object sender, EventArgs e)
25 {
26 HttpApplication app = sender as HttpApplication;
27 if (app != null)
28 {
29 HttpContext context = app.Context;
30 HttpResponse response = app.Response;
31 response.Write("自定义HttpModule中的EndRequest");
32
33 }
34 }
35
36 void context_BeginRequest(object sender, EventArgs e)
37 {
38 HttpApplication app = sender as HttpApplication;
39 if (app != null)
40 {
41 HttpContext context = app.Context;
42 HttpResponse response = app.Response;
43 response.Write("自定义HttpModule中的BeginRequest");
44
45 }
46 }
47 }
48 }
在web.config注册自定义的HttpModule
1 <?xml version="1.0" encoding="utf-8"?> 2 <!-- 3 For more information on how to configure your ASP.NET application, please visit 4 http://go.microsoft.com/fwlink/?LinkId=169433 5 --> 6 <configuration> 7 <system.web> 8 <compilation debug="true" targetFramework="4.5" /> 9 <httpRuntime targetFramework="4.5" /> 10 11 </system.web> 12 <system.webServer> 13 <modules> 14 <add name="MyHttpModule" type="MyHttpModule.MyHttpModule,MyHttpModule"/> 15 </modules> 16 </system.webServer> 17 </configuration>
浏览页面Default.aspx
那么在生命周期过程中的一系列的事件的执行顺序是怎样的呢？
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Web;
5
6 namespace MyHttpModule
7 {
8 /// <summary>
9 /// 自定义HttpModule
10 /// </summary>
11 public class MyHttpModule : IHttpModule
12 {
13 public void Dispose()
14 {
15 throw new NotImplementedException();
16 }
17
18 public void Init(HttpApplication context)
19 {
20 context.BeginRequest += context_BeginRequest;
21 context.EndRequest += context_EndRequest;
22 context.PostAcquireRequestState += context_PostAcquireRequestState;
23 context.PostAuthenticateRequest += context_PostAuthenticateRequest;
24 context.PostAuthorizeRequest += context_PostAuthorizeRequest;
25 context.PostLogRequest += context_PostLogRequest;
26 context.PostMapRequestHandler += context_PostMapRequestHandler;
27 context.PostRequestHandlerExecute += context_PostRequestHandlerExecute;
28 context.PostResolveRequestCache += context_PostResolveRequestCache;
29 context.PostUpdateRequestCache += context_PostUpdateRequestCache;
30 context.PreRequestHandlerExecute += context_PreRequestHandlerExecute;
31 context.PreSendRequestContent += context_PreSendRequestContent;
32 context.PreSendRequestHeaders += context_PreSendRequestHeaders;
33 context.RequestCompleted += context_RequestCompleted;
34 context.ResolveRequestCache += context_ResolveRequestCache;
35 context.UpdateRequestCache += context_UpdateRequestCache;
36 context.ReleaseRequestState += context_ReleaseRequestState;
37 }
38
39 void context_UpdateRequestCache(object sender, EventArgs e)
40 {
41 HttpApplication app = sender as HttpApplication;
42 if (app != null)
43 {
44 HttpContext context = app.Context;
45 HttpResponse response = app.Response;
46 response.Write("自定义HttpModule中的UpdateRequestCache<br/>");
47 }
48 }
49
50 void context_ResolveRequestCache(object sender, EventArgs e)
51 {
52 HttpApplication app = sender as HttpApplication;
53 if (app != null)
54 {
55 HttpContext context = app.Context;
56 HttpResponse response = app.Response;
57 response.Write("自定义HttpModule中的ResolveRequestCache<br/>");
58 }
59 }
60
61 void context_RequestCompleted(object sender, EventArgs e)
62 {
63 HttpApplication app = sender as HttpApplication;
64 if (app != null)
65 {
66 HttpContext context = app.Context;
67 HttpResponse response = app.Response;
68 response.Write("自定义HttpModule中的RequestCompleted<br/>");
69 }
70 }
71
72 void context_PreSendRequestHeaders(object sender, EventArgs e)
73 {
74 HttpApplication app = sender as HttpApplication;
75 if (app != null)
76 {
77 HttpContext context = app.Context;
78 HttpResponse response = app.Response;
79 response.Write("自定义HttpModule中的PreSendRequestHeaders<br/>");
80 }
81 }
82
83 void context_PreSendRequestContent(object sender, EventArgs e)
84 {
85 HttpApplication app = sender as HttpApplication;
86 if (app != null)
87 {
88 HttpContext context = app.Context;
89 HttpResponse response = app.Response;
90 response.Write("自定义HttpModule中的PreSendRequestContent<br/>");
91 }
92 }
93
94 void context_PreRequestHandlerExecute(object sender, EventArgs e)
95 {
96 HttpApplication app = sender as HttpApplication;
97 if (app != null)
98 {
99 HttpContext context = app.Context;
100 HttpResponse response = app.Response;
101 response.Write("自定义HttpModule中的PreRequestHandlerExecute<br/>");
102 }
103 }
104
105 void context_PostUpdateRequestCache(object sender, EventArgs e)
106 {
107 HttpApplication app = sender as HttpApplication;
108 if (app != null)
109 {
110 HttpContext context = app.Context;
111 HttpResponse response = app.Response;
112 response.Write("自定义HttpModule中的PostUpdateRequestCache<br/>");
113 }
114 }
115
116 void context_PostResolveRequestCache(object sender, EventArgs e)
117 {
118 HttpApplication app = sender as HttpApplication;
119 if (app != null)
120 {
121 HttpContext context = app.Context;
122 HttpResponse response = app.Response;
123 response.Write("自定义HttpModule中的PostResolveRequestCache<br/>");
124 }
125 }
126
127 void context_PostRequestHandlerExecute(object sender, EventArgs e)
128 {
129 HttpApplication app = sender as HttpApplication;
130 if (app != null)
131 {
132 HttpContext context = app.Context;
133 HttpResponse response = app.Response;
134 response.Write("自定义HttpModule中的PostRequestHandlerExecut<br/>");
135 }
136 }
137
138 void context_PostMapRequestHandler(object sender, EventArgs e)
139 {
140 HttpApplication app = sender as HttpApplication;
141 if (app != null)
142 {
143 HttpContext context = app.Context;
144 HttpResponse response = app.Response;
145 response.Write("自定义HttpModule中的PostMapRequestHandler<br/>");
146 }
147 }
148
149 void context_PostLogRequest(object sender, EventArgs e)
150 {
151 HttpApplication app = sender as HttpApplication;
152 if (app != null)
153 {
154 HttpContext context = app.Context;
155 HttpResponse response = app.Response;
156 response.Write("自定义HttpModule中的PostLogRequest<br/>");
157 }
158 }
159
160 void context_PostAuthorizeRequest(object sender, EventArgs e)
161 {
162 HttpApplication app = sender as HttpApplication;
163 if (app != null)
164 {
165 HttpContext context = app.Context;
166 HttpResponse response = app.Response;
167 response.Write("自定义HttpModule中的PostAuthorizeRequest<br/>");
168 }
169 }
170
171 void context_PostAuthenticateRequest(object sender, EventArgs e)
172 {
173 HttpApplication app = sender as HttpApplication;
174 if (app != null)
175 {
176 HttpContext context = app.Context;
177 HttpResponse response = app.Response;
178 response.Write("自定义HttpModule中的PostAuthenticateRequest<br/>");
179 }
180 }
181
182 void context_PostAcquireRequestState(object sender, EventArgs e)
183 {
184 HttpApplication app = sender as HttpApplication;
185 if (app != null)
186 {
187 HttpContext context = app.Context;
188 HttpResponse response = app.Response;
189 response.Write("自定义HttpModule中的PostAcquireRequestState<br/>");
190 }
191 }
192
193 void context_ReleaseRequestState(object sender, EventArgs e)
194 {
195 HttpApplication app = sender as HttpApplication;
196 if (app != null)
197 {
198 HttpContext context = app.Context;
199 HttpResponse response = app.Response;
200 response.Write("自定义HttpModule中的ReleaseRequestState<br/>");
201 }
202 }
203
204 void context_EndRequest(object sender, EventArgs e)
205 {
206 HttpApplication app = sender as HttpApplication;
207 if (app != null)
208 {
209 HttpContext context = app.Context;
210 HttpResponse response = app.Response;
211 response.Write("自定义HttpModule中的EndRequest<br/>");
212 }
213 }
214
215 void context_BeginRequest(object sender, EventArgs e)
216 {
217 HttpApplication app = sender as HttpApplication;
218 if (app != null)
219 {
220 HttpContext context = app.Context;
221 HttpResponse response = app.Response;
222 response.Write("自定义HttpModule中的BeginRequest<br/>");
223
224 }
225 }
226 }
227 }
浏览结果
使用HttpModule终止此次Http请求
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 using System.Web;
7 namespace MyHttpModule
8 {
9 public class EndModule : IHttpModule
10 {
11 public void Dispose()
12 {
13 throw new NotImplementedException();
14 }
15
16 public void Init(HttpApplication context)
17 {
18 context.BeginRequest += context_BeginRequest;
19 }
20
21 void context_BeginRequest(object sender, EventArgs e)
22 {
23 HttpApplication application = (HttpApplication)sender;
24
25 application.CompleteRequest();
26
27 application.Context.Response.Write("请求被终止。");
28
29 }
30 }
31 }
结果
总结
这里介绍了在asp.net生命周期中一个最重要的接口IHttpModule，可以这样来形容该接口，事件接口，因为在实现类中的Init方法中，可以注册生命周期中的各种事件，并可以在事件中定义各种逻辑。
参考文章
一点一点学ASP.NET之基础概念——HttpModule 文野
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时间： 2025-01-30 16:46:06