asp.net frameworke处理程序的作用

1 向客户端发送响应的工作都由处理程序完成

2 任何实现System.web.ihttpHandler接口的类都可以作为传入的http请求的目标

3 如果需要重复使用自定义处理程序对象，需要创建自定义处理程序工厂。

4 如何创建自定义处理程序

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Handlers
{
    public class CustomHandler : IHttpHandler
    {
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        public void ProcessRequest(HttpContext context)
        {
            string time = DateTime.Now.ToShortTimeString();
            if (context.Request.CurrentExecutionFilePathExtension==".json")
            {
                context.Response.ContentType = "application/json";
                context.Response.Write(string.Format("{{\"time\":\"{0}\"}}", time));
            }
            else
            {
                context.Response.ContentType = "text/html";
                context.Response.Write(string.Format("<span>{0}</span>", time));
            }
        }
    }
}

在web.config文件中注册自定义的处理程序

<system.webServer>
<handlers>
<add name="customJson" path="*.json" verb="GET" type="Handlers.CustomHandler"/>
<add name="customText" path="Time.text" verb="*" type="Handlers.CustomHandler"/>
</handlers>
</system.webServer>

5 如何创建自定义的处理程序工厂

自定义处理程序工厂是实现IHttpHandlerFactory接口的类，他负责生成用于响应的IHttpHandler对象

首先创建实现IHttpHandlerFactory接口的实例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Handlers
{
    public class InstanceControlFactory : IHttpHandlerFactory
    {
        private int factoryCounter = ;
        public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
        {
            return new InstanceControlHandler(factoryCounter++);
        }

        public void ReleaseHandler(IHttpHandler handler)
        {
            throw new NotImplementedException();
        }
    }

    public class InstanceControlHandler : IHttpHandler
    {
        private int v;

        public InstanceControlHandler(int v)
        {
            this.v = v;
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            context.Response.Write(string.Format("the counter value is {0}",v));
        }
    }
}

其次在web.config文件中注册实现IHttpHandlerFactory接口的类

  <system.webServer>
    <handlers>
      <add name="customJson" path="*.json" verb="GET" type="Handlers.CustomHandler"/>
      <add name="customText" path="Time.text" verb="*" type="Handlers.CustomHandler"/>
      <add name="InstanceControl" path="*.instance" verb="*" type="Handlers.InstanceControlFactory"/>
    </handlers>
  </system.webServer>

6 如何重复的使用处理程序，将同一个处理程序对象应用于多个不同的请求