private DownloadFileResult downloadFileWithCheckpoint(DownloadFileRequest downloadFileRequest)
throws Throwable {
DownloadFileResult downloadFileResult = new DownloadFileResult();
DownloadCheckPoint downloadCheckPoint = new DownloadCheckPoint();
// 开启断点续传，从checkpoint文件读取上次分片下载的结果
if (downloadFileRequest.isEnableCheckpoint()) {
// 从checkpoint文件读取上次下载结果，checkpoint文件不存在/文件被篡改/被破坏时，从新下载
try {
downloadCheckPoint.load(downloadFileRequest.getCheckpointFile());
} catch (Exception e) {
remove(downloadFileRequest.getCheckpointFile());
}
// 上传的文件修改了，从新下载
if (!downloadCheckPoint.isValid(objectOperation)) {
prepare(downloadCheckPoint, downloadFileRequest);
remove(downloadFileRequest.getCheckpointFile());
}
} else {
// 没有开启断点下载功能，从新下载
prepare(downloadCheckPoint, downloadFileRequest);
}
// 并发下载分片
DownloadResult downloadResult = download(downloadCheckPoint, downloadFileRequest);
for (PartResult partResult : downloadResult.getPartResults()) {
if (partResult.isFailed()) {
throw partResult.getException();
}
}
// 开启了断点下载，成功上传后删除checkpoint文件
if (downloadFileRequest.isEnableCheckpoint()) {
remove(downloadFileRequest.getCheckpointFile());
}
downloadFileResult.setObjectMetadata(downloadResult.getObjectMetadata());
return downloadFileResult;
}
private void prepare(
DownloadCheckPoint downloadCheckPoint, DownloadFileRequest downloadFileRequest)
throws IOException {
downloadCheckPoint.magic = DownloadCheckPoint.DOWNLOAD_MAGIC;
downloadCheckPoint.downloadFile = downloadFileRequest.getDownloadFile();
downloadCheckPoint.bucketName = downloadFileRequest.getBucketName();
downloadCheckPoint.objectKey = downloadFileRequest.getKey();
downloadCheckPoint.objectStat =
ObjectStat.getFileStat(
objectOperation, downloadCheckPoint.bucketName, downloadCheckPoint.objectKey);
downloadCheckPoint.downloadParts =
splitFile(downloadCheckPoint.objectStat.size, downloadFileRequest.getPartSize());
createFixedFile(downloadFileRequest.getDownloadFile(), downloadCheckPoint.objectStat.size);
}
