一、HttpModule：经过多个HttpModule,层层处理
HttpHandler:请求的终点，最终的处理
1.首先创建一个网站，然后添加两个ASP.NET页面，并创建一个HttpModule类
namespace WebApplication1
{
public class HttpModelu : IHttpHandler
{
public bool IsReusable
{
get
{
return true;
}
}
public void ProcessRequest(HttpContext context)
{
Uri lastUrl = context.Request.UrlReferrer;
Uri currenUrl = context.Request.Url;
if (lastUrl.Host != currenUrl.Host || lastUrl.Port != currenUrl.Port)
{
string errorImagePath = context.Request.PhysicalApplicationPath + "Error/04.jpg";
context.Response.WriteFile(errorImagePath);
}
else
{
context.Response.WriteFile(context.Request.PhysicalPath);
}
}
}
}
2.配置信息，实现了HttpModule类，还需要在web.confing中配置，在<configuration>节点下添加如下代码：
<system.webServer>
<handlers>
<add verb="*" path="Images/*" type="WebApplication1.HttpModelu" name="plink"/>
</handlers>
</system.webServer>
3.创建站点
1）创建被盗站点。首先创建包含了jpg图片资源的网站，然后添加一个aspx页面，插入本网站提供的三张图片，代码如下：
<div>
<asp:Image ID="Image1" runat="server" ImageUrl="~/Images/01.jpg" />
<asp:Image ID="Image2" runat="server" ImageUrl="~/Images/02.jpg" />
<asp:Image ID="Image3" runat="server" ImageUrl="~/Images/03.jpg" />
</div>
2)创建盗链站点。创建第二个网点，添加aspx页面，引用第一个网站提供的三张图片，代码如下：
<div>
<asp:Image ID="Image1" runat="server" ImageUrl="http://localhost:61014/Images/01.jpg" />
<asp:Image ID="Image2" runat="server" ImageUrl="http://localhost:61014/Images/02.jpg"/>
<asp:Image ID="Image3" runat="server" ImageUrl="http://localhost:61014/Images/03.jpg"/>
</div>
二、图片水印
1.创建第一个网站，准备其图片资源
在网站中添加TestHandel类，继承IHttpHandler接口，编写加水印的功能，代码如下：
namespace WebApplication3
{
public class TestHandel : IHttpHandler
{
private const string WATERMARK_URL = "~/Images/01.jpg";
private const string DEFAULTIME_URL = "~/Error/04.jpg";
public bool IsReusable
{
get
{
return false;
}
}
public void ProcessRequest(HttpContext context)
{
string filePath = context.Request.PhysicalPath;
System.Drawing.Image Cover;
if (File.Exists(filePath))
{
Cover = Image.FromFile(filePath);
Image watermark = Image.FromFile(context.Server.MapPath(WATERMARK_URL));
Graphics G = Graphics.FromImage(Cover);
G.DrawImage(watermark, new Rectangle(Cover.Width - watermark.Width,
Cover.Height - watermark.Height, watermark.Width, watermark.Height), 0,
0, watermark.Width, watermark.Height, GraphicsUnit.Pixel);
G.Dispose();
watermark.Dispose();
}
else
{
Cover = Image.FromFile(context.Request.MapPath(DEFAULTIME_URL));
}
context.Response.ContentType = "Images/jpeg";
Cover.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
Cover.Dispose();
context.Response.End();
}
}
}
2.在Web.coning中配置实现当请求图片资源时由TestHandel类处理，配置如下：
<system.webServer>
<handlers>
<add verb="*" path="Images/*.jpg" type="WebApplication3.TestHandel" name="handerl1"/>
</handlers>
</system.webServer>
3.添加Web页面，展示图片，部分代码如下：
<div>
<asp:Image ID="Image1" runat="server" ImageUrl="~/Images/02.jpg" />
<asp:Image ID="Image2" runat="server" ImageUrl="~/Images/03.jpg" />
</div>
三、验证码
1.创建一个网站，并在网站中添加VerificationCode 类，继承IHttpHandler与IRequiresSessionState接口，代码如下：
namespace WebApplication3
{
public class VerificationCode : IHttpHandler,IRequiresSessionState
{
private Random RandomSeed = new Random();
public bool IsReusable => false;
public void ProcessRequest(HttpContext context)
{
string strWord = "3456789QWERTYUPAS2DFGHKXCVBNM";
string NumStr = null;
for (int i = 0; i < 5; i++)
{
NumStr += strWord[RandomSeed.Next(0, strWord.Length)];
}
context.Session["vcode"] = NumStr.ToLower();
CreateImages(context, NumStr);
}
private void CreateImages(HttpContext context, string numStr)
{
int iwidth = (int)(numStr.Length * 13);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 22);
Graphics g = Graphics.FromImage(image);
g.Clear(Color.White);
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
string[] font = { "宋体", "微软雅黑" };
Random rand = new Random();
for (int i = 0; i < 50; i++)
{
int x = rand.Next(image.Width);
int y = rand.Next(image.Height);
g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
}
for (int i = 0; i < numStr.Length; i++)
{
int cindex = rand.Next(7);
int findex = rand.Next(5);
Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
int ii = 4;
if ((i + 1) % 2 == 0)
{
ii = 2;
}
g.DrawString(numStr.Substring(i, 1), f, b, 2 + (i * 12), ii);
}
g.DrawRectangle(new Pen(ColorTranslator.FromHtml("#CCCCCC"), 0), 0, 0, image.Width - 1, image.Height - 1);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
context.Response.ClearContent();
context.Response.ContentType = "image/gif";
context.Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}
}
}
2、添加一个Web窗体，登录使用验证码实现登录验证功能
页面代码如下：
<body>
<form id="form1" runat="server">
<div>
<table style="width:100%;" border="1" cellspacing="0" cellpadding="0">
<tr>
<td>账号：</td>
<td><asp:TextBox ID="TextBox1" runat="server"></asp:TextBox></td>
</tr>
<tr>
<td>密码：</td>
<td><asp:TextBox ID="TextBox2" runat="server"></asp:TextBox></td>
</tr>
<tr>
<td>验证码：</td>
<td><asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
<asp:Image ID="Image1" runat="server" ImageUrl="VerificationCode.cs" />
<asp:LinkButton ID="LinkButton1" runat="server">刷新</asp:LinkButton>
</td>
</tr>
</table>
<asp:Button ID="Button1" runat="server" Text="提交" style="margin-left:50%;margin-top:2%" OnClick="Button1_Click" />
</div>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
</form>
</body>
后台部分代码（点击Button事件）
protected void Button1_Click(object sender, EventArgs e)
{
string account = this.TextBox1.Text;
string password = this.TextBox2.Text;
string code = this.TextBox3.Text;
if (Session["vcode"].ToString() == code.ToLower())
{
if(account=="admin" && password == "123456")
{
Response.Redirect("WebForm1.aspx");
}
else
{
Label1.Text = "账号或者密码不正确！";
}
}
else
{
Label1.Text = "验证码不正确";
}
}
