动态验证码

package servlet;
/**
* @姚伟男
*/
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
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;

/**
* Servlet implementation class CodeImage
*/
public class CodeImage extends HttpServlet {
private static final long serialVersionUID = 1L;
      
    /**
     * @see HttpServlet#HttpServlet()
     */
private final int width=50;
private final int height=20;
private final int num=5;
private Random random=new Random();
private int red,blue,green;
private Graphics g;
private BufferedImage image=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
private String code;
private char[] ch={'0','1','2','3','4','5','6','7','8','9'};
    public CodeImage() {
        super();
      
    }

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
code="";  
g=image.getGraphics();
        red=random.nextInt(255);
        blue=random.nextInt(255);
        green=random.nextInt(255);
        Color c=new Color(red, green, blue);
        g.setColor(c);
        g.fillRect(0, 0, width, height);
        for(int i=0;i<num;i++){
        int index=random.nextInt(10);
        code+=ch[index]+"";
        }
        c=new Color(5, 45, 67);
        g.setColor(c);
        g.setFont(new Font("黑体", Font.BOLD,18));
        g.drawString(code, 0, 15);
        g.dispose();
        request.getSession().setAttribute("code", code);
        ImageIO.write(image, "JPEG", response.getOutputStream());
}

}