class Base64Coder {

    public static byte[] decryptBASE64(String str){  
		if(str==null || str.length()==0){
			return null;
		}
	    byte[] bt = null;  
	    sun.misc.BASE64Decoder decoder = new sun.misc.BASE64Decoder();  
	    try {
			bt = decoder.decodeBuffer(str);
		} catch (IOException e) {
			throw new RuntimeException("decrypt base64 error.", e);
		}  
        return bt;  
    }

}