带用验证码功能的用户登录 -学习笔记
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- )验证码使用一个CheckCodeSerlvet产生，通过<img src=""/>发送请求，将验证码绑定到HttpSession中
- )产生的验证码一定要在输出到浏览器之前绑定到HttpSession中
- )设置验证码禁止缓存要在输出到浏览器之前
- )所有响应头的设置放置在最先
java代码
LoginServlet
import java.io.IOException;
import java.io.PrintWriter;
import java.util.zip.Checksum;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 收集客户端填入的验证码
String checkCodeClient = request.getParameter("checkCodeClient");
// 取得服务端填入的验证码
String checkCodeServer = (String) request.getSession().getAttribute(
"checkCodeServer");
// 设置字体
response.setContentType("text/html;charset=UTF-8");
//判断的。通过客户端与服务端
if (checkCodeClient != null && checkCodeClient.trim().length() > 0
&& checkCodeServer != null
&& checkCodeServer.equals(checkCodeClient)) {
response.getWriter().write("验证码正确");
} else {
response.getWriter().write("验证码出错");
}
}
}CheckCodeServlet
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class CheckCodeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//缓存
response.setHeader("expires","-1");
response.setHeader("cache-control","no-cache"); //没有缓成
response.setHeader("pragma","no-cache");
String token = Token.getNum();
//将验证码绑定到域对象
HttpSession session = request.getSession();
session.setAttribute("checkCodeServer",token);
//在内存生存一个图片
BufferedImage image = new BufferedImage(50,25,BufferedImage.TYPE_INT_RGB);
//获取画笔
Graphics g = image.getGraphics();
//设置大小
g.drawString(token,15,15);
//增加干扰线
for(int i=0;i<10;i++)
{
Random r = new Random();
int x1 = r.nextInt(50);
int y1 = r.nextInt(25);
g.drawLine(x1, y1, x1+4,y1+4);
}
//写到浏览器
ImageIO.write(image,"JPG",response.getOutputStream());
}
}
//用于产生随机数
class Token{
public static String getNum(){
Random r = new Random();
int num = r.nextInt(10000);
return num + "";
}
}html代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login.html</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
<form action="/day04/LoginServlet" method="post">
<table border="1" align="center">
<caption>用户登陆验证码</caption>
<tr>
<th>用户名</th>
<td><input type="text" name="username"/></td>
</tr>
<tr>
<th>密码</th>
<td><input type="password" name="password"/></td>
</tr>
<tr>
<th>验证码</th>
<td>
<input type="text" name="checkCodeClient"/>
</td>
<td>
<img src="/day04/CheckCodeServlet"/>
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="提交"/>
</td>
</tr>
</table>
</form>
</body>
</html>
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