spring mvc 通过字节流返回图像

/**
* 通过url请求返回图像的字节流
*/
@RequestMapping("icon/{cateogry}")
public void getIcon(@PathVariable("cateogry") String cateogry,
HttpServletRequest request,
HttpServletResponse response) throws IOException {

if(StringUtils.isEmpty(cateogry)) {
cateogry = "";
}

String fileName = request.getSession().getServletContext().getRealPath("/")
+ "resource\\icons\\auth\\"
+ cateogry.toUpperCase().trim() + ".png";

File file = new File(fileName);

//判断文件是否存在如果不存在就返回默认图标
if(!(file.exists() && file.canRead())) {
file = new File(request.getSession().getServletContext().getRealPath("/")
+ "resource/icons/auth/root.png");
}

FileInputStream inputStream = new FileInputStream(file);
byte[] data = new byte[(int)file.length()];
int length = inputStream.read(data);
inputStream.close();

response.setContentType("image/png");

OutputStream stream = response.getOutputStream();
stream.write(data);
stream.flush();
stream.close();
}