InputStream转为byte数组

InputStream is = request.getSession().getServletContext().getResourceAsStream("/WEB-INF/swdjzbg.png");
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        int len = 1024;
        byte tmp [] = new byte[len];
        int i ;
        while((i=is.read(tmp, 0, len))>0){
            baos.write(tmp, 0, i);
        }
        byte imgs[] = baos.toByteArray();