Java生成与JSP验证的验证码实现

1、GetYZMImage.java

public class GetYZMImage extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.getSession().removeAttribute("yzm");
BufferedImage img = new BufferedImage(64, 25,
BufferedImage.TYPE_4BYTE_ABGR);
Graphics g = img.getGraphics();
Random r = new Random();
Color c = new Color(255, 255, 255);
g.setColor(c);
g.fillRect(0, 0, 64, 25);
StringBuffer sb = new StringBuffer();
char[] ch = "ACDEFGHJKLMNPQRSTUVWXYZ2345679".toCharArray();
int index, len = ch.length;
for (int i = 0; i < 4; i++) {
index = r.nextInt(len);
g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255)));
g.setFont(new Font("Arial", Font.BOLD | Font.ITALIC, 16 + r
.nextInt(14)));// 输出的字体和大小
g.drawString("" + ch[index], (i * 15) + 3, 18);// 写什么数字，在图片的什么位置画
sb.append(ch[index]);
}
//System.err.println(MP_MD5.md5(sb.toString()));
request.getSession().setAttribute("yzm", MD5.md5(sb.toString().toLowerCase()));

// String yzm= (String)request.getSession().getAttribute("yzm");
// System.err.println(yzm);