@Controller
public class ValidateCodeController {
  private static final long serialVersionUID = 1L;
  private static int WIDTH = 70;        // 驗(yàn)證碼圖片的寬度
  private static int HEIGHT = 35;      // 驗(yàn)證碼圖片的高度
  @RequestMapping("/validateCode")
  public void validateCode(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    HttpSession session = request.getSession();
    response.setContentType("image/jpeg");
    ServletOutputStream sos = response.getOutputStream();
    // 設(shè)置瀏覽器不要緩存該圖片
    response.setHeader("Pragma", "No-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setDateHeader("Expires", 0);
    // 創(chuàng)建圖片緩存區(qū)
    BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    Graphics g = image.getGraphics();          // 獲取畫筆
    char [] rands = generateCheckCode();      // 產(chǎn)生隨機(jī)的驗(yàn)證碼
    // 產(chǎn)生圖像
    drawBackground(g);
    drawRands(g, rands);
    // 結(jié)束繪畫過程，完成圖像
    g.dispose();
    // 將圖像輸出到客戶端
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ImageIO.write(image, "JPEG", bos);
    byte [] buf = bos.toByteArray();
    response.setContentLength(buf.length);
    sos.write(buf);
    bos.close();
    sos.close();
    // 將當(dāng)前驗(yàn)證碼存入 Session 中
    session.setAttribute("valicode", new String(rands));
    //System.out.println("1:"+request.getSession().getId());
    System.out.println(session.getAttribute("valicode"));
  }
  private void drawRands(Graphics g, char[] rands) {
    g.setColor(new Color(41, 41, 41));
    g.setFont(new Font(null, Font.ITALIC|Font.BOLD, 18));
    g.drawString("" + rands[0], 2, 17);
    g.drawString(" " + rands[1], 16, 20);
    g.drawString(" " + rands[2], 31, 13);
    g.drawString(" " + rands[3], 46, 18);
    //System.out.println(rands);
  }
  private void drawBackground(Graphics g) {
    g.setColor(new Color(255, 255, 255));
    g.fillRect(0, 0, WIDTH, HEIGHT);
    // 隨機(jī)產(chǎn)生 120 個(gè)干擾點(diǎn)
    for(int i = 0; i < 120; i++) {
      int x = (int) (Math.random() * WIDTH);
      int y = (int) (Math.random() * HEIGHT);
      int red = (int) (Math.random() * 255);
      int green = (int) (Math.random() * 255);
      int blue = (int) (Math.random() * 255);
      g.setColor(new Color(red, green, blue));
      g.drawOval(x, y, 1, 0);
    }
  }
  // 生成四個(gè)字符的驗(yàn)證碼
  private char[] generateCheckCode() {
    String chars = "0123456789abcdefghijklmnopqrstuvwxyz";
    char [] rands = new char[4];
    for(int i = 0; i <4; i++) {
      int rand = (int) (Math.random() * 36);
      rands[i] = chars.charAt(rand);
    }
    return rands;
  }
}