验证码技术（severlet）
severlet代码
web.xml 配置
//目前遇到一个问题是，加上strutst2 的filter之后就不行，明天解决。
解决方法：
package com.kewei.ssh;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ValidationCodeServlet extends HttpServlet {
// Process the HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 设置页面不缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
// 设置图片的长宽
int width = 62, height = 22;
// ////// 创建内存图像
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 获取图形上下文
Graphics g = image.createGraphics();
// 设定图像背景色(因为是做背景，所以偏淡)
g.setColor(getRandColor(180, 250));
g.fillRect(0, 0, width, height);
// 设置字体
g.setFont(new Font("Times New Roman", Font.PLAIN, 17));
// /////设置默认生成4个验证码
int length = 4;
java.util.Random rand = new Random(); // 设置随机种子
/*
* if (request.getParameter("length") != null) { try { length =
* Integer.parseInt(request.getParameter("length")); }catch
* (NumberFormatException e) {} }
*/
// 设置备选验证码:包括"a-z"和数字"0-9"
String base = "abcdefghijklmnopqrstuvwxyz0123456789";
int size = base.length();
StringBuffer str = new StringBuffer();
for (int i = 0; i < length; i++) {
int start = rand.nextInt(size);
String tmpStr = base.substring(start, start + 1);
str.append(tmpStr);
// 生成随机颜色(因为是做前景，所以偏深)
g.setColor(getRandColor(10, 150));
// 将此字画到图片上
// g.drawString(str.toString(), 4, 17);
g.drawString(tmpStr, 13 * i + 6 + rand.nextInt(5), 14 + rand
.nextInt(6));
}
// 将认证码存入session
request.getSession().setAttribute("valiCode", str.toString());
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
// 给定范围获得一个随机颜色
Color getRandColor(int fc, int bc) {
Random random = new Random();
if (fc > 255)
fc = 255;
if (bc > 255)
bc = 255;
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
}
web.xml 配置
<servlet>
<servlet-name>VolidateCode</servlet-name>
<servlet-class>com.kewei.ssh.ValidationCodeServlet</servlet-class>
<load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>VolidateCode</servlet-name>
<url-pattern>/VolidateCode</url-pattern>
</servlet-mapping>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="utf-8"%> <title>验证码</title> <html> 验证码： <img width="62" height="22" src="VolidateCode" /> </html>
//目前遇到一个问题是，加上strutst2 的filter之后就不行，明天解决。
解决方法：
<filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>*.action</url-pattern> </filter-mapping> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>*.jsp</url-pattern> </filter-mapping>