在一次ASP.NET请求处理过程中，HttpHandler和HttpModule一样都可以截获的这个请求并做一些额外的工作。
他们的区别在于：
（1）对于HTTP请求而言，HttpModule是HTTP请求的“必经之路”，HttpModule可以有多个，每次HTTP请求都将逐一通过每个HttpModule。无论客户端请求什么类型文件，都会调用HttpModule。
（2）HttpHandler是请求的处理中心，按照你的请求生成响应的内容。可自定义什么情况下调用HttpHandler。
（3）ASP.Net处理请求时，使用（管道）方式，由各个HttpModule对请求进行处理，然后到达 HttpHandler，HttpHandler处理完之后，再交给HttpModule处理，最后将HTML发送到客户端浏览器中。HttpModule中的事件有的在HttpHandler之前，有的在之后。
一、HttpHandler实现验证码
0094.PNG
在项目中创建一般处理程序文件“ValidateImageHandle.ashx”。
<%@ WebHandler Language="C#" Class="ValidateImageHandle" %>
using System;
using System.Web;
using System.Drawing;
/*
HttpHandler中默认是不能使用Session的。
解决方法：
1、读取Session时：实现System.Web.SessionState.IReadOnlySessionState接口，无任何方法（只是一个标记作用）
2、保存Session时：实现System.Web.SessionState.IRequiresSessionState接口
*/
public class ValidateImageHandle : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{
public void ProcessRequest (HttpContext context) {
//context.Response.ContentType = "text/plain";
//context.Response.Write("Hello World");
string strCode = CreateRnd();
context.Session["validate"] = strCode;
byte[] bytes = CreateImage(strCode);
context.Response.ContentType = "image/gif";
context.Response.BinaryWrite(bytes);
}
public bool IsReusable {
get {
return false;
}
}
#region 生成随机验证码
public string CreateRnd()
{
Random Rnd = new Random();
string RndChars = "";
char code;
for (int i = 1; i <= 4; i++)
{
if (Rnd.Next() % 2 == 0) //偶数生成数字
{
code = (char)('0' + Rnd.Next(0, 10));
}
else //奇数生成字母
{
code = (char)('A' + Rnd.Next(0, 10));
}
RndChars = RndChars + code.ToString();
}
return RndChars;
}
#endregion
#region 将验证码生成图片
public byte[] CreateImage(string RndChars)
{
Random Rnd = new Random();
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(RndChars.Length * 15, 26);
Graphics g = Graphics.FromImage(bitmap);
g.Clear(Color.Gray); //清空图片，设置背景为灰色
//画图片噪线
for (int i = 1; i <= Rnd.Next(10, 30); i++)
{
int x1 = Rnd.Next(1, bitmap.Width);
int x2 = Rnd.Next(1, bitmap.Width);
int y1 = Rnd.Next(1, bitmap.Height);
int y2 = Rnd.Next(1, bitmap.Height);
g.DrawLine(new Pen(Color.Green), x1, y1, x2, y2);
}
//画验证码字符串
Font font = new Font("微软雅黑", 12, (FontStyle.Bold | FontStyle.Italic));
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new RectangleF(0, 0, bitmap.Width, bitmap.Height), Color.Red, Color.Blue, 1.2f, true);
g.DrawString(RndChars, font, brush, 2, 2);
//画图片噪点
for (int i = 0; i <= Rnd.Next(50, 100); i++)
{
int x = Rnd.Next(1, bitmap.Width);
int y = Rnd.Next(1, bitmap.Height);
bitmap.SetPixel(x, y, Color.Red);
}
//画图片边框线
g.DrawRectangle(new Pen(Color.Black), 0, 0, bitmap.Width - 1, bitmap.Height - 1);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
return ms.ToArray();
}
#endregion
}
用户登录使用验证码：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>httpHandler实现验证码</title>
<script src="js/jquery.js" type="text/javascript"></script>
<style type="text/css">
#container{ text-align:center;}
.righttd
{
width: 460px;
}
.lefted
{
width: 196px;
}
.mytitle{ font-size:18px; font-weight:bold;}
</style>
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">
//alert(new Date());
$(function () {
$("#Refresh").click(function () {
$("#imgValidate").prop("src", "ValidateImageHandle.ashx?date=" + new Date());
})
})
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<h1>httpHandler实现验证码-先复习之前案例中验证码的实现</h1>
<table>
<tr>
<td align="center" height="30" class="mytitle" colspan="2">用户登录</td>
</tr>
<tr>
<td align="right" class="lefted" height="30">用户名:</td>
<td align="left" class="righttd" height="30">
<asp:TextBox ID="txtAccount" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td align="right" class="lefted" height="30">密码:</td>
<td align="left" class="righttd" height="30">
<asp:TextBox ID="txtPwd" runat="server" TextMode="Password"></asp:TextBox>
</td>
</tr>
<tr>
<td align="right" class="lefted" height="30">验证码:</td>
<td align="left" class="righttd" height="30">
<asp:TextBox ID="txtValidate" runat="server" Width="72px"></asp:TextBox>
<asp:Image ID="imgValidate" runat="server" ImageUrl="~/ValidateImageHandle.ashx" />
<a href="javascript:void(0);" id="Refresh">刷新</a>
</td>
</tr>
<tr>
<td align="right" class="lefted" height="30"></td>
<td align="left" class="righttd" height="30">
<asp:Button ID="btLogin" runat="server" Text="登 录" onclick="btLogin_Click" />
</td>
</tr>
<tr>
<td align="right" class="lefted" height="30"></td>
<td align="left" class="righttd" height="30">
<asp:Label ID="lblErrInfo" runat="server" ForeColor="Red"></asp:Label>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
public partial class Demo01 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
#region 登录
protected void btLogin_Click(object sender, EventArgs e)
{
if (Session["validate"] == null)
{
this.lblErrInfo.Text = "验证码过期";
this.imgValidate.ImageUrl = "~/ValidateImageHandle.ashx"; //加载验证码
return;
}
if (this.txtValidate.Text.Equals(Session["validate"].ToString()) == false)
{
this.lblErrInfo.Text = "验证码错误!";
}
else
{
this.lblErrInfo.Text = "验证码正确";
}
}
#endregion
}
二、HttpHandler实现图片水印
HttpHandler实现图片水印在此文中有两种方式来实现：
（1）创建ashx文件进行二次绘图，C#程序中调用ashx文件实现水印添加。
（2）创建CS类文件进行二次绘图，通过配置文件配置路径规则给指定路径下的文件实现水印添加。
方案一
在项目中创建一般处理程序文件“ImgHandler.ashx”。
<%@ WebHandler Language="C#" Class="ImgHandler" %>
using System;
using System.Web;
using System.Drawing;
public class ImgHandler : IHttpHandler {
public void ProcessRequest (HttpContext context) {
//context.Response.ContentType = "text/plain";
//context.Response.Write("Hello World");
string vpath = context.Request.QueryString["ImageUrl"]; //虚拟路径
string ppath = context.Server.MapPath(vpath); //根据虚拟路径获得物理路径
Image img = Image.FromFile(ppath); //根据绝对路径获取图片
Graphics gh = Graphics.FromImage(img); //绘画对象
Image imgWaterMark = Image.FromFile(context.Server.MapPath("~/img/watermark.png"));
float w = img.Width;
float h = img.Height;
float x = 6;
float y = 6;
gh.DrawImage(imgWaterMark, x, y, w, h); //进行二次绘图
context.Response.ContentType = "image/jpeg";
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
public bool IsReusable {
get {
return false;
}
}
}
页面中实现图片水印：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>httpHandle给图片添加水印</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Panel ID="pnlImages" runat="server">
<asp:Image ID="Image2" runat="server" Width="200" Height="240" ImageUrl="~/img/book/5566e4b4Nb156fe14.jpg" />
<asp:Image ID="Image3" runat="server" Width="200" Height="240" ImageUrl="~/img/book/5573e4b4Nb1561288.jpg" />
<asp:Image ID="Image5" runat="server" Width="200" Height="240" ImageUrl="~/img/book/55b8a409N20918431.jpg" />
<asp:Image ID="Image6" runat="server" Width="200" Height="240" ImageUrl="~/img/book/9787020096466.jpg" />
<asp:Image ID="Image7" runat="server" Width="200" Height="240" ImageUrl="~/img/book/9787020096473.jpg" />
</asp:Panel>
</div>
</form>
</body>
</html>
public partial class Demo02 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
foreach (Control obj in pnlImages.Controls)
{
Image img = obj as Image;
if (img != null)
{
string imgurl = img.ImageUrl;
img.ImageUrl = "~/ImgHandler.ashx?ImageUrl=" + Server.UrlEncode(imgurl);
}
}
}
}
方案二
在App_Code文件夹创建“MyImgHandler.cs”文件。
public class MyImgHandler:IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
//context.Response.ContentType = "text/plain";
//context.Response.Write("Hello World");
string vpath = context.Request.Path; //获取配置文件中配置的路径
string ppath = context.Server.MapPath(vpath); //根据虚拟路径获得物理路径
Image img = Image.FromFile(ppath); //根据绝对路径获取图片
Graphics gh = Graphics.FromImage(img); //绘画对象
Image imgWaterMark = Image.FromFile(context.Server.MapPath("~/img/watermark.png"));
float w = img.Width;
float h = img.Height;
float x = 6;
float y = 6;
gh.DrawImage(imgWaterMark, x, y, w, h); //进行二次绘图
//context.Response.ContentType = "image/jpeg";
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
public bool IsReusable
{
get
{
return false;
}
}
}
根目录web.config配置文件：
<?xml version="1.0"?>
<!--
有关如何配置 ASP.NET 应用程序的详细信息，请访问
http://go.microsoft.com/fwlink/?LinkId=169433
-->
<configuration>
<system.web>
<compilation debug="true" targetFramework="4.0"/>
<!--IIS6配置-->
<httpHandlers>
<add type="MyImgHandler" path="img/book/*.*" verb="*"/>
</httpHandlers>
</system.web>
<!--IIS7配置-->
<!--<system.webServer>
<handlers>
<add name="MyImgHandler" path="img/book/*.*" type="MyImgHandler" verb="*"/>
</handlers>
</system.webServer>-->
</configuration>
页面测试水印效果：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>httpHandle给图片添加水印-将Handle写在类文件中用配置文件来调用</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Panel ID="pnlImages" runat="server">
<asp:Image ID="Image2" runat="server" Width="200" Height="240" ImageUrl="~/img/book/5566e4b4Nb156fe14.jpg" />
<asp:Image ID="Image3" runat="server" Width="200" Height="240" ImageUrl="~/img/book/5573e4b4Nb1561288.jpg" />
<asp:Image ID="Image5" runat="server" Width="200" Height="240" ImageUrl="~/img/book/55b8a409N20918431.jpg" />
<asp:Image ID="Image6" runat="server" Width="200" Height="240" ImageUrl="~/img/book/9787020096466.jpg" />
<asp:Image ID="Image7" runat="server" Width="200" Height="240" ImageUrl="~/img/book/9787020096473.jpg" />
</asp:Panel>
</div>
<div>
<asp:Image ID="Image1" runat="server" Width="200" Height="240" ImageUrl="~/img/nba/lunnade.jpg" />
<asp:Image ID="Image4" runat="server" Width="200" Height="240" ImageUrl="~/img/nba/maidi.jpg" />
<asp:Image ID="Image8" runat="server" Width="200" Height="240" ImageUrl="~/img/nba/nashi.jpg" />
</div>
</form>
</body>
</html>
