OSS在上传文件完成时支持提供回调（Callback）给应用服务器。您只需要在发送给OSS的请求中携带相应的Callback参数，即可实现回调。本文介绍如何使用上传回调。

说明 由于加入了回调请求和响应的过程，相比简单上传，使用回调通知机制一般会导致客户端花费更多的等待时间。 
PutObjectRequest put = new PutObjectRequest(testBucket, testObject, uploadFilePath);

put.setCallbackParam(new HashMap<String, String>() {
    {
        put("callbackUrl", "192.168.10.106/callback");
        put("callbackHost", "yourCallbackHost");
        put("callbackBodyType", "application/json");
        put("callbackBody", "{\"mimeType\":${mimeType},\"size\":${size}}");
    }
});

OSSAsyncTask task = oss.asyncPutObject(put, new OSSCompletedCallback<PutObjectRequest, PutObjectResult>() {
    @Override
    public void onSuccess(PutObjectRequest request, PutObjectResult result) {
        Log.d("PutObject", "UploadSuccess");

        // 只有设置了servercallback，该值才有数据。
        String serverCallbackReturnJson = result.getServerCallbackReturnBody();

        Log.d("servercallback", serverCallbackReturnJson);
    }

    @Override
    public void onFailure(PutObjectRequest request, ClientException clientExcepion, ServiceException serviceException) {
        // 异常处理。
    }
});

如果需要支持自定义参数，请参考如下示例设置：

put.setCallbackParam(new HashMap<String, String>() {
    {
        put("callbackUrl", "http://192.168.192.125/leibin/notify.php");
        put("callbackHost", "yourCallbackHost");
        put("callbackBodyType", "application/json");
        put("callbackBody", "{\"object\":${object},\"size\":${size},\"my_var1\":${x:var1},\"my_var2\":${x:var2}}");
    }
});

put.setCallbackVars(new HashMap<String, String>() {
    {
        put("x:var1", "value1");
        put("x:var2", "value2");
    }
});

关于Callback的更多信息，请参见API参考中的Callback。