验证码

ImgUtil:

package org.xxx.util;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
public class AuthImg extends HttpServlet {
private static final long serialVersionUID = 1L;
//设置字体
private Font mFont = new Font("Arial Black", Font.PLAIN, 16);
public void init() throws ServletException {
  super.init();
}
  /**
     * 生成随机颜色
     * @param fc 产生颜色值下限(lower limit)
     * @param bc 产生颜色值上限(upper limit)
     * @return 生成的随机颜色对象
     */
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);
}

public void service(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  response.setHeader("Pragma", "no-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);
  response.setContentType("image/jpeg");
 
  int width = 100, height = 18;
  //生成画布
  BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
  //获取图形上下文 （生成画笔）
  Graphics g = image.getGraphics();
  Random random = new Random();
  //设置背景色（）
  g.setColor(getRandColor(200, 250));
  //填充矩形区域 ，作为背景
  g.fillRect(1, 1, width - 1, height - 1);
   //设置边框颜色
  g.setColor(new Color(102, 102, 102));
  g.drawRect(0, 0, width - 1, height - 1);
  g.setFont(mFont);
  //设置随机干扰线条颜色
  g.setColor(getRandColor(160, 200));
  //产生155条干扰线条
  for (int i = 0; i < 155; i++) {
   int x = random.nextInt(width - 1);
   int y = random.nextInt(height - 1);
   int xl = random.nextInt(6) + 1;
   int yl = random.nextInt(12) + 1;
   g.drawLine(x, y, x + xl, y + yl);
  }
  for (int i = 0; i < 70; i++) {
   int x = random.nextInt(width - 1);
   int y = random.nextInt(height - 1);
   int xl = random.nextInt(12) + 1;
   int yl = random.nextInt(6) + 1;
   g.drawLine(x, y, x - xl, y - yl);
  }

  String sRand = "";
  for (int i = 0; i < 6; i++) {
   String tmp = getRandomChar();
   sRand += tmp;
   g.setColor(new Color(20 + random.nextInt(110), 20 + random
     .nextInt(110), 20 + random.nextInt(110)));
   g.drawString(tmp, 15 * i + 10, 15);
  }

  HttpSession session = request.getSession(true);
  session.setAttribute("rand", sRand);
  g.dispose();
  ImageIO.write(image, "JPEG", response.getOutputStream());
}

private String getRandomChar() {
  //int rand = (int) Math.round(Math.random() * 2);
  long itmp = 0;
  /*char ctmp = '\u0000';
  switch (rand) {
  case 1:
   itmp = Math.round(Math.random() * 25 + 65);
   ctmp = (char) itmp;
   return String.valueOf(ctmp);
  case 2:
   itmp = Math.round(Math.random() * 25 + 97);
   ctmp = (char) itmp;
   return String.valueOf(ctmp);
  default:*/
   itmp = Math.round(Math.random() * 9);
   return String.valueOf(itmp);
  //}
}
}

页面:

显示验证码 <img src="authImg" name="auimg" id="auimg"></img>

刷新验证码
function refresh(){
$("#auimg").attr("src","authImg?now="+new Date());
}

后台:

后台取得验证码
String varCode = (String) session.get("rand");
if(inputString==varCode).....


web.xml配置:
<servlet>
  <servlet-name>authimg</servlet-name>
  <servlet-class>org.xxx.util.AuthImg</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>authimg</servlet-name>
  <url-pattern>/authImg</url-pattern>
</servlet-mapping>