在asp.net程序中，我们可以通过配置url的path路径的方式，将某个path路径下的请求交给指定的IHttpHandler去处理，这便是对request请求进行编程。
一、新建一个framework类库
该类库中包含我们需要的IHttpHandler处理程序。
新建一个名为ApiHttpHandler的类，并继承IHttpHandler接口。如下代码：
namespace MyHttpHandler{ ???public class ApiHttpHandler : IHttpHandler ???{ ???????public bool IsReusable => true; ???????public void ProcessRequest(HttpContext context) ???????{ ???????????context.Response.Write("ApiHttpHandler"); ???????} ???}}二、新建一个空的项目
将IHttpHandler配置到web.config的handlers节点，如下所示：
<system.webServer> ???<handlers> ?????<!--使用单个IHttpHandler--> ?????<add name="apiHttpHandler" type="MyHttpHandler.ApiHttpHandler,MyHttpHandler" path="/api/*" verb="*"/> ????????</handlers> ?</system.webServer>
name:在配置文件中对当前handler自定义的名称；
type:组成格式 "handler类名,handler所在的程序集名称"；
path:当前handler需要处理的请求的path路径；
verb:请求的方式，如：Post,Get等。
新建一些html页面来测试，web项目程序结构如下：
Login.html就是默认的首页，在项目的属性中配置：
Login.html页面内容如下：
启动程序，查看结果：
三、使用IHttpHandlerFactory配置多个IHttpHandler
新建一个MultiHandler类，继承IHttpHandlerFactory。如下代码：
namespace MyHttpHandler{ ???//使用IHttpHandlerFactory来集中管理多个HttpHandler的处理 ???public class MultiHandler : IHttpHandlerFactory ???{ ???????//自定义的字典，key为路径,value为对应的IHttpHandler处理器 ???????protected IDictionary<string, IHttpHandler> handlers = new Dictionary<string, IHttpHandler> { ???????????{ "book",new BookHttpHandler()}, ???????????{ "student",new StudentHttpHandler()} ???????}; ???????//返回一个实现了IHttpHandler接口的实例； ???????public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated) ???????{ ???????????IHttpHandler rc = null; ???????????????//根据第一级路径名来区分 ???????????//如 /apis/book/* 需要BookHttpHandler来处理 ???????????var path = context.Request.Path?.Split(new string[] { "/"},StringSplitOptions.RemoveEmptyEntries)?.Skip(1)?.Take(1)?.FirstOrDefault()??""; ???????????if (handlers.Keys.Contains(path.ToLower())) ???????????????rc = handlers[path]; ???????????else rc = new DefaultHandler(); ???????????????????????return rc; ???????} ???????//使得Factory可以重复使用一个已经存在Handler实例。 ???????public void ReleaseHandler(IHttpHandler handler) ???????{ ??????????// throw new NotImplementedException(); ???????} ???} ???}web项目的web.config如下配置：
<system.webServer> ???<handlers> ?????<!--使用单个IHttpHandler--> ?????<add name="apiHttpHandler" type="MyHttpHandler.ApiHttpHandler,MyHttpHandler" path="/api/*" verb="*"/> ?????<add name="fileHttpHandler" type="MyHttpHandler.FileHttpHandler,MyHttpHandler" path="/file/*" verb="POST"/> ?????<!--使用IHttpHandlerFactory来集中管理多个HttpHandler的处理--> ?????<add name="multiHandlers" type="MyHttpHandler.MultiHandler,MyHttpHandler" path="/apis/*" verb="*"/> ???</handlers> ?</system.webServer>
Login.html的内容如下：
<!DOCTYPE html><html><head> ???<meta charset="utf-8" /> ???<title></title></head><body> ???<div id="app"> ???????apiResp:{{apiResp}} ???????<br /> ???????fileResp: {{fileResp}} ???????<br /> ???????bookResp: {{bookResp}} ???????<br /> ???????studentResp: {{studentResp}} ???????<br /> ???????defaultResp: {{defaultResp}} ???????<br /> ???????<button @click.self.prevent="turnToHome">转到home页面</button> ???</div> ???<script src="js/vue.js"></script> ???<script src="js/jquery-3.3.1.min.js"></script> ???<script> ???????var app = new Vue({ ???????????el: "#app", ???????????data: { ???????????????apiResp: "", ???????????????fileResp: "", ???????????????bookResp: "", ???????????????studentResp: "", ???????????????defaultResp:"" ???????????}, ???????????methods: { ???????????????turnToHome: function (event) { ???????????????????window.location.href = "html/Home.html"; ???????????????} ???????????}, ???????????created: function () { ???????????????//this.resp = "hello"; ???????????????var that = this; ???????????????$.ajax({ ???????????????????type: "post", ???????????????????url: "/api/hello", ???????????????????data: null, ???????????????????contentType: "text/plain", ???????????????????success: function (data) { ???????????????????????if (data) ???????????????????????????that.apiResp = data; ???????????????????????else that.apiResp = "no data"; ???????????????????}, ???????????????????error: function (err) { ???????????????????????that.apiResp = "error"; ???????????????????} ???????????????}); ???????????????$.ajax({ ???????????????????type: "post", ???????????????????url: "/file/hello", ???????????????????data: null, ???????????????????contentType: "text/plain", ???????????????????success: function (data) { ???????????????????????if (data) ???????????????????????????that.fileResp = data; ???????????????????????else that.fileResp = "no data"; ???????????????????}, ???????????????????error: function (err) { ???????????????????????that.fileResp = "error"; ???????????????????} ???????????????}); ???????????????$.ajax({ ???????????????????type: "post", ???????????????????url: "/apis/book/hello", ???????????????????data: null, ???????????????????contentType: "text/plain", ???????????????????success: function (data) { ???????????????????????if (data) ???????????????????????????that.bookResp = data; ???????????????????????else that.bookResp = "no data"; ???????????????????}, ???????????????????error: function (err) { ???????????????????????that.bookResp = "error"; ???????????????????} ???????????????}); ???????????????$.ajax({ ???????????????????type: "post", ???????????????????url: "/apis/student/hello", ???????????????????data: null, ???????????????????contentType: "text/plain", ???????????????????success: function (data) { ???????????????????????if (data) ???????????????????????????that.studentResp = data; ???????????????????????else that.studentResp = "no data"; ???????????????????}, ???????????????????error: function (err) { ???????????????????????that.studentResp = "error"; ???????????????????} ???????????????}); ???????????????$.ajax({ ???????????????????type: "post", ???????????????????url: "/apis/default/hello", ???????????????????data: null, ???????????????????contentType: "text/plain", ???????????????????success: function (data) { ???????????????????????if (data) ???????????????????????????that.defaultResp = data; ???????????????????????else that.defaultResp = "no data"; ???????????????????}, ???????????????????error: function (err) { ???????????????????????that.defaultResp = "error"; ???????????????????} ???????????????}); ???????????} ???????????????????}); ???</script></body></html>启动程序后的结果如下图所示：
我们可以使用IHttpHandler来实现图片的防盗链和其他的功能，用处多多！
参考文档：http://www.cnblogs.com/JimmyZhang/archive/2007/09/15/894124.html
asp.net IHttpHandler浅析
原文地址：https://www.cnblogs.com/williamwsj/p/10264520.html