jsp做验证码的生成

jsp做验证码的生成 悬赏分：10 | 解决时间：2007-7-3 10:04 | 提问者：ncut224
请问哪位高手帮忙解决一下，怎样用jsp编写验证码的产生，最好是能把具体用到的函数也给注释或解释的详细一些，谢谢咯，最好能再补充一些学习jsp的心得和建议，谢谢了，小弟初学。
最佳答案 用Serverlet编写！以下是验证码的产生代码！你可以研究一下！


public class ValidateCodeServlet extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 4008416931787800531L;

/**
* Constructor of the object.
*/
public ValidateCodeServlet() {
super();
}

/**
* Destruction of the servlet.

*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
}

/**
* The doGet method of the servlet.

*
* This method is called when a form has its tag value method equals to get.
*
* @param request
* the request send by the client to the server
* @param response
* the response send by the server to the client
* @throws ServletException
* if an error occurred
* @throws IOException
* if an error occurred
*/
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);

// 在内存中创建图象
int width = 60, height = 20;
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);

// 获取绘画对象
Graphics g = image.getGraphics();
// 设定背景色
g.setColor(getRandColor(225, 250));
g.fillRect(0, 0, width, height);
//设定字体
g.setFont(new Font("Times New Roman", Font.BOLD, 20));

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
Random random = new Random();
g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}

// 取随机产生的认证码(4位数字)
String sRand = "";
for (int i = 0; i < 4; i++) {
String rand = String.valueOf(random.nextInt(10));
sRand += rand;
// 将认证码显示到图象中
g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(rand, 13 * i + 6, 16);
}

// 将认证码存入SESSION
HttpSession session = request.getSession();
session.setAttribute("valicode", sRand);

// 图象生效
g.dispose();

// 输出图象到页面
Image

IO.write(image, "JPEG", response.getOutputStream());

}

/**
* The doPost method of the servlet.

*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}

/**
* 给定范围获得随机颜色
* @param fc
* @param bc
* @return
*/
private 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);
}

}