图片处理签名出错，按照文档做的，帮忙看看是不是哪里弄错？

以下为错误提示：


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<Error>

<Code>SignatureDoesNotMatch</Code>
<Message>The request signature we calculated does not match the signature you provided. Check your key and signing method.</Message>
<RequestId>54544E4165CC6367EB0DD555</RequestId>
<HostId>image.soso88.org</HostId>
</Error>


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以下为代码片段：

/**      * 实现阿里云签名实现以及相关URL请求必要的URL参数，参数使用在URL的?号后面部分。
     * 此处实现的URL是基于网络抓取频道下的URL链接      * @param key        访问的资源文件名
     * @param param        访问的资源图片处理参数（OSS协议对图片的处理）      * @param time        访问的URL有效时间，过期后访问URL无效
     * @return            返回最终的URL参数（OSS协议）      * @throws UnsupportedEncodingException
     */     public static String getDownLoadUrlStr(String key,String param, int time) throws UnsupportedEncodingException{
        StringBuffer urlBuf = new StringBuffer();         int realtime = DateUtilExt.parseNowToInt()+time;
        urlBuf.append("OSSAccessKeyId=").append(URLEncoder.encode(ACCESS_ID, "utf-8"));         urlBuf.append("&");
        urlBuf.append("Expires=").append(realtime);         urlBuf.append("&");
        String canonicalizedResource = "/" + downloadBucketName + "/" + key + "@" + param;         urlBuf.append("Signature=").append(URLEncoder.encode(getSignature(canonicalizedResource, realtime), "utf-8"));
        return urlBuf.toString();     }


public static final String GET_METHOD = "GET";    private static String getSignature(String canonicalizedResource, int time){
        StringBuffer buf = new StringBuffer();        buf.append(GET_METHOD);
        buf.append("\n");        buf.append("\n");
        buf.append("\n");        buf.append(time);
        buf.append("\n");        buf.append(canonicalizedResource);
        return Codec.encodeBASE64(buf.toString());    }