動態產生密碼圖片

DynamicImage.java

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Iterator;

import javax.imageio.ImageIO;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageOutputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DynamicImage extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        BufferedImage bi = new BufferedImage(50,30,BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = bi.createGraphics();
        g2d.setColor(Color.white);
        g2d.fillRect(0, 0, 50, 30);
        g2d.setColor(Color.black);
        g2d.drawRect(5, 5, 40, 20);
  
        StringBuilder sbl = new StringBuilder();
        while(sbl.length() < 4){
                sbl.append(Integer.toString((int)(Math.random() * 9)));
        }
  
        g2d.setFont(new Font("Default",Font.BOLD,13));
        g2d.drawString(sbl.toString(), 10, 20);
  
        for(int i = 0; i < 20; i++){
                int x = (int)(Math.random() * 40) + 5;
                int y = (int)(Math.random() * 20) + 5;
   
                g2d.fillOval(x, y, 1, 1);
        }
  
        response.setContentType("image/jpeg");
        ServletOutputStream sos = response.getOutputStream();
  
        Iterator ite = ImageIO.getImageWritersByFormatName("jpeg");
        ImageWriter iw = (ImageWriter)ite.next();
  
        ImageOutputStream ios = ImageIO.createImageOutputStream(sos);
        iw.setOutput(ios);
        iw.write(bi);
        ios.flush();
        sos.close();
    }
}