/**
   * 根据图片的地址，返回图片的缓冲流
   * @param addr
   * @return
   */
  public static BufferedImage getInputStream(String addr){
    try {
      String imgPath = addr; 
      BufferedImage image = ImageIO.read(new FileInputStream(imgPath));
      return image;
    } catch (Exception e) {
      e.printStackTrace();
      System.out.println();
      System.out.println("获取图片异常:java.awt.image.BufferedImage");
      System.out.println("请检查图片路径是否正确，或者该地址是否为一个图片");
    }
    return null;
  }

/**
   * 根据图片的地址，来获取图片
   * @param addr
   * @param response
   */
  @ResponseBody
  @RequestMapping("/getImg")
  public void getImg(@Param("addr")String addr,HttpServletResponse response){
    BufferedImage img = new BufferedImage(300, 150, BufferedImage.TYPE_INT_RGB);
    img = ImgUtil.getInputStream(addr);
    if(img==null){
      throw new RuntimeException("打印图片异常：com.controller.Business_Ctrl.getImg(String, HttpServletResponse)");
    }
    if(img!=null){
      try {
        ImageIO.write(img, "JPEG", response.getOutputStream());
      } catch (IOException e) {
        e.printStackTrace();
        System.out.println("打印异常:com.controller.Business_Ctrl.getImg(String, HttpServletResponse)");
      }
    }
  }

ifModified Boolean Default: false 
Allow the request to be successful only if the response has changed since the last request. This is done by checking the Last-Modified header. Default value is false, ignoring the header. 
cache Boolean Default: true 
Added in jQuery 1.2, if set to false it will force the pages that you request to not be cached by the browser. 
$.ajax({
type: "GET",
url: "static/cache.js",
dataType: "text",
cache:false,
ifModified :true
});