servlet输出随机验证码-蒲公英云

servlet输出随机验证码

傷城~ 2022-08-12 01:05 242阅读 0赞

public static final int WIDTH = 120;
    public static final int HEIGHT = 25;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        //1、设置背景色
        setBackGroud(g);
        //2.设置边框    
        setBorder(g);
        //3.画干扰线
        drawRandomLine(g);
        //4.写随机数
        drawRandomNum((Graphics2D)g);
        //5.图形写给浏览器 
        response.setContentType("image/jpeg");
        //发图控制浏览器不要缓存
        response.setDateHeader("expries", -1);
        response.setHeader("cache-control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        ImageIO.write(image, "jpg", response.getOutputStream());
    }
    private void setBackGroud(Graphics g) {
        g.setColor(Color.WHITE);
        //填充矩形
        g.fillRect(0, 0, WIDTH, HEIGHT);
    }
    private void setBorder(Graphics g) {
        g.setColor(Color.BLUE);
        g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
    }
    private void drawRandomLine(Graphics g) {
        g.setColor(Color.GREEN);
        for(int i=0; i<5; i++){
            int x1 = new Random().nextInt(WIDTH);
            int y1 = new Random().nextInt(HEIGHT);
            int x2 = new Random().nextInt(WIDTH);
            int y2 = new Random().nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);
        }
    }
    private void drawRandomNum(Graphics2D g) {
        g.setColor(Color.RED);
        g.setFont(new Font("宋体",Font.BOLD,20));
        //中文字所在区间  [\u4e00-\u9fa5]
        String base = "ABCDEFGHIJK";
        int x = 10;
        for(int i=0; i<4; i++){
            //设置旋转角度
            int degree = new Random().nextInt()%30;//生成正负30内数
            String ch = base.charAt(new Random().nextInt(base.length()))+"";
            g.rotate(degree*Math.PI/180, x, 20);
            g.drawString(ch, x, 20);
            g.rotate(-degree*Math.PI/180, x, 20);//旋转回去
            x+=30;
        }
    }