IHttpModule和IHttpHandler 应用笔记
ASP.NET 提供了 IHttpHandler 和 IHttpModule 接口,它可使您使用与在 IIS 中所用的 Internet 服务器 API (ISAPI) 编程接口同样强大的 API,而且具有更简单的编程模型。HTTP 处理程序对象与 IIS ISAPI 扩展的功能相似,而 HTTP 模块对象与 IIS ISAPI 筛选器的功能相似。
ASP.NET 将 HTTP 请求映射到 HTTP 处理程序上。每个 HTTP 处理程序都会启用应用程序内单个的 HTTP URL 处理或 URL 扩展组处理。HTTP 处理程序具有和 ISAPI 扩展相同的功能,同时具有更简单的编程模型。
HTTP 模块是处理事件的程序集。ASP.NET 包括应用程序可使用的一组 HTTP 模块。例如,ASP.NET 提供的 SessionStateModule 向应用程序提供会话状态服务。也可以创建自定义的 HTTP 模块以响应 ASP.NET 事件或用户事件。
关于HttpModule的注册、应用方法请参看我的另一篇博文:
关于IHttpHandler的应用,我们先从它的注册方法讲起。
当你建立了一个实现了Ihttphandler接口的类后,可以在网站的web.config文件中注册这个httphandler
示例如下:
<httpHandlers>
<remove verb="*" path="*.asmx"/>
<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add verb="*" path="*.ho" type="WebApplication2.HelloHandler,WebApplication2"/>
</httpHandlers>
<remove verb="*" path="*.asmx"/>
<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add verb="*" path="*.ho" type="WebApplication2.HelloHandler,WebApplication2"/>
</httpHandlers>
其中最后一行 <add verb="*" path="*.ho" type="WebApplication2.HelloHandler,WebApplication2"/>
便是我们手工加入的内容,WebApplication2.HelloHandler是实现了IhttpHandler接口的一个类,Path属性表示的是映射的文件格式。
这样注册好之后,如果从网站请求任何带后缀名.ho的文件时,就会转到WebApplication2.HelloHandler类进行处理。
而WebApplication2.HelloHandler的内容可以是在网页上打印一行文本(如下面代码),也可以是下载一个文件,反正在httphandler里面你可以控制response对象的输出。
下面代码示例打印一行文字的WebApplication2.HelloHandler源码:
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
namespace WebApplication2
{
public class HelloHandler:IHttpHandler
{
#region IHttpHandler
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/html";
context.Response.Write("<html>");
context.Response.Write("<body>");
context.Response.Write("<b>Response by HelloHandler!</B>");
context.Response.Write("</body>");
context.Response.Write("</html>");
}
public bool IsReusable
{
get
{ return true; }
}
#endregion
}
}
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
namespace WebApplication2
{
public class HelloHandler:IHttpHandler
{
#region IHttpHandler
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/html";
context.Response.Write("<html>");
context.Response.Write("<body>");
context.Response.Write("<b>Response by HelloHandler!</B>");
context.Response.Write("</body>");
context.Response.Write("</html>");
}
public bool IsReusable
{
get
{ return true; }
}
#endregion
}
}
以下内容为转载的IhttpHandler示例:利用IhttpHandler实现文件下载
1. 首先新建一个用于下载文件的page页,如download.aspx,里面什么东西也没有。
2. 添加一个DownloadHandler类,它继承于IHttpHandler接口,可以用来自定义HTTP 处理程序同步处理HTTP的请求。
using System.Web;
using System;
using System.IO;
public class DownloadHandler : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
HttpResponse Response = context.Response;
HttpRequest Request = context.Request;
System.IO.Stream iStream = null;
byte[] buffer = new Byte[10240];
int length;
long dataToRead;
try
{
string filename = FileHelper.Decrypt(Request["fn"]); //通过解密得到文件名
string filepath = HttpContext.Current.Server.MapPath("~/") + "files/" + filename; //待下载的文件路径
iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
System.IO.FileAccess.Read, System.IO.FileShare.Read);
Response.Clear();
dataToRead = iStream.Length;
long p = 0;
if (Request.Headers["Range"] != null)
{
Response.StatusCode = 206;
p = long.Parse(Request.Headers["Range"].Replace("bytes=", "").Replace("-", ""));
}
if (p != 0)
{
Response.AddHeader("Content-Range", "bytes " + p.ToString() + "-" + ((long) (dataToRead - 1)).ToString() + "/" + dataToRead.ToString());
}
Response.AddHeader("Content-Length", ((long) (dataToRead - p)).ToString());
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode(System.Text.Encoding.GetEncoding(65001).GetBytes(Path.GetFileName(filename))));
iStream.Position = p;
dataToRead = dataToRead - p;
while (dataToRead > 0)
{
if (Response.IsClientConnected)
{
length = iStream.Read(buffer, 0, 10240);
Response.OutputStream.Write(buffer, 0, length);
Response.Flush();
buffer = new Byte[10240];
dataToRead = dataToRead - length;
}
else
{
dataToRead = -1;
}
}
}
catch (Exception ex)
{
Response.Write("Error : " + ex.Message);
}
finally
{
if (iStream != null)
{
iStream.Close();
}
Response.End();
}
}
public bool IsReusable
{
get { return true; }
}
}
using System;
using System.IO;
public class DownloadHandler : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
HttpResponse Response = context.Response;
HttpRequest Request = context.Request;
System.IO.Stream iStream = null;
byte[] buffer = new Byte[10240];
int length;
long dataToRead;
try
{
string filename = FileHelper.Decrypt(Request["fn"]); //通过解密得到文件名
string filepath = HttpContext.Current.Server.MapPath("~/") + "files/" + filename; //待下载的文件路径
iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
System.IO.FileAccess.Read, System.IO.FileShare.Read);
Response.Clear();
dataToRead = iStream.Length;
long p = 0;
if (Request.Headers["Range"] != null)
{
Response.StatusCode = 206;
p = long.Parse(Request.Headers["Range"].Replace("bytes=", "").Replace("-", ""));
}
if (p != 0)
{
Response.AddHeader("Content-Range", "bytes " + p.ToString() + "-" + ((long) (dataToRead - 1)).ToString() + "/" + dataToRead.ToString());
}
Response.AddHeader("Content-Length", ((long) (dataToRead - p)).ToString());
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode(System.Text.Encoding.GetEncoding(65001).GetBytes(Path.GetFileName(filename))));
iStream.Position = p;
dataToRead = dataToRead - p;
while (dataToRead > 0)
{
if (Response.IsClientConnected)
{
length = iStream.Read(buffer, 0, 10240);
Response.OutputStream.Write(buffer, 0, length);
Response.Flush();
buffer = new Byte[10240];
dataToRead = dataToRead - length;
}
else
{
dataToRead = -1;
}
}
}
catch (Exception ex)
{
Response.Write("Error : " + ex.Message);
}
finally
{
if (iStream != null)
{
iStream.Close();
}
Response.End();
}
}
public bool IsReusable
{
get { return true; }
}
}
3. 这里涉及到一个文件名加解密的问题,是为了防止文件具体名称暴露在状态栏中,所以添加一个FileHelper类,代码如下:
public class FileHelper
{
public static string Encrypt(string filename)
{
byte[] buffer = HttpContext.Current.Request.ContentEncoding.GetBytes(filename);
return HttpUtility.UrlEncode(Convert.ToBase64String(buffer));
}
public static string Decrypt(string encryptfilename)
{
byte[] buffer = Convert.FromBase64String(encryptfilename);
return HttpContext.Current.Request.ContentEncoding.GetString(buffer);
}
}
{
public static string Encrypt(string filename)
{
byte[] buffer = HttpContext.Current.Request.ContentEncoding.GetBytes(filename);
return HttpUtility.UrlEncode(Convert.ToBase64String(buffer));
}
public static string Decrypt(string encryptfilename)
{
byte[] buffer = Convert.FromBase64String(encryptfilename);
return HttpContext.Current.Request.ContentEncoding.GetString(buffer);
}
}
利用Base64码对文件名进行加解密处理。
4. 在Web.config上,添加httpHandlers结点,如下:
<system.web>
<httpHandlers>
<add verb="*" path="download.aspx" type="DownloadHandler" />
</httpHandlers>
</system.web>
<httpHandlers>
<add verb="*" path="download.aspx" type="DownloadHandler" />
</httpHandlers>
</system.web>
5. 现在新建一个aspx页面,对文件进行下载:
Default.aspx代码如下:
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>文件下载</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:HyperLink ID="link" runat="server" Text="文件下载"></asp:HyperLink>
</div>
</form>
</body>
</html>
Default.aspx.cs代码如下:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string url = FileHelper.Encrypt("DesignPattern.chm");
link.NavigateUrl = "~/download.aspx?fn=" + url;
}
}
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string url = FileHelper.Encrypt("DesignPattern.chm");
link.NavigateUrl = "~/download.aspx?fn=" + url;
}
}
这样就实现了文件下载时,不管是什么格式的文件,都能够弹出打开/保存窗口。
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