response-实现验证码

public static final int WIDTH =120;    public static final int HEIGHT= 25;    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)     */    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        setBackGround(g);        //2.设置边框        setBorder(g);        //3.画干扰线        drawRandomLine(g);        //4.写随机数        drawRandomNum((Graphics2D)g);        //5.写给浏览器        response.setContentType("image/jpeg");        //发头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 drawRandomNum(Graphics2D g) {        g.setColor(Color.RED);        g.setFont(new Font("宋体",Font.BOLD,20));        String base = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a";        //{\u4e00-\u9fa5}        int x=5;        for (int i = 0; i < 4; i++) {            int degree = new Random().nextInt()%30;            String ch =base.charAt(new Random().nextInt(base.length()))+"";            g.rotate(degree*Math.PI/180,x,20);//设置旋转角度            g.drawString(ch, x, 20);            g.rotate(-degree*Math.PI/180,x,20);            x+=30;        }    }    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 setBorder(Graphics g) {        g.setColor(Color.BLUE);        g.drawRect(1, 1, WIDTH-2,HEIGHT-2);    }    private void setBackGround(Graphics g) {        g.setColor(Color.WHITE);        g.fillRect(0, 0, WIDTH, HEIGHT);    }