public DownloadFileResult downloadFile(DownloadFileRequest downloadFileRequest) throws Throwable {
assertParameterNotNull(downloadFileRequest, "downloadFileRequest");
String bucketName = downloadFileRequest.getBucketName();
String key = downloadFileRequest.getKey();
assertParameterNotNull(bucketName, "bucketName");
assertParameterNotNull(key, "key");
ensureBucketNameValid(bucketName);
ensureObjectKeyValid(key);
// 没有指定本地文件，使用key作为本地文件名称
if (downloadFileRequest.getDownloadFile() == null) {
downloadFileRequest.setDownloadFile(downloadFileRequest.getKey());
}
// 开启断点续传，没有指定checkpoint文件，使用默认值
if (downloadFileRequest.isEnableCheckpoint()) {
if (downloadFileRequest.getCheckpointFile() == null
|| downloadFileRequest.getCheckpointFile().isEmpty()) {
downloadFileRequest.setCheckpointFile(downloadFileRequest.getDownloadFile() + ".dcp");
}
}
return downloadFileWithCheckpoint(downloadFileRequest);
}
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;
}