java實現簡易驗證碼

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    int width=100;
    int height=50;
    BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
    Graphics g=image.getGraphics();

    //填充背景色
    g.setColor(Color.pink);
    g.fillRect(0,0,width,height);

    //畫邊框
    g.setColor(Color.BLUE);
    g.drawRect(0,0,width-1 ,height-1);

    String str="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    Random random=new Random();
    for (int i = 1; i <=4; i++) {
        int i1 = random.nextInt(str.length());
        char c = str.charAt(i1);
        g.drawString(c+"",20*i,height/2);
    }

    g.setColor(Color.CYAN);
    for (int i = 1; i <=5; i++) {
        int x1 = random.nextInt(width);
        int x2 = random.nextInt(width);

        int y1 = random.nextInt(height);
        int y2 = random.nextInt(height);
       g.drawLine(x1,y1,x2,y2);
    }
    ImageIO.write(image,"jpg",response.getOutputStream());

}