问题
Let's say I have 50 objects (15Mb each) stored in Google Cloud Storage. Now I need to create a zip archive containing all of them and store the resultant file back at GCS. How can I do that from within an appengine java app?
回答1:
I wrote the method below which seems to be working fine.
public static void zipFiles(final GcsFilename targetZipFile,
final GcsFilename... filesToZip) throws IOException {
Preconditions.checkArgument(targetZipFile != null);
Preconditions.checkArgument(filesToZip != null);
Preconditions.checkArgument(filesToZip.length > 0);
final int fetchSize = 4 * 1024 * 1024;
final int readSize = 2 * 1024 * 1024;
GcsOutputChannel outputChannel = null;
ZipOutputStream zip = null;
try {
GcsFileOptions options = new GcsFileOptions.Builder().mimeType(MediaType.ZIP.toString()).build();
outputChannel = GCS_SERVICE.createOrReplace(targetZipFile, options);
zip = new ZipOutputStream(Channels.newOutputStream(outputChannel));
GcsInputChannel readChannel = null;
for (GcsFilename file : filesToZip) {
try {
final GcsFileMetadata meta = GCS_SERVICE.getMetadata(file);
if (meta == null) {
LOGGER.warning(file.toString() + " NOT FOUND. Skipping.");
continue;
}
//int fileSize = (int) meta.getLength();
// LOGGER.fine("adding " + file.toString());
ZipEntry entry = new ZipEntry(file.getObjectName());
zip.putNextEntry(entry);
readChannel = GCS_SERVICE.openPrefetchingReadChannel(file, 0, fetchSize);
final ByteBuffer buffer = ByteBuffer.allocate(readSize);
int bytesRead = 0;
while (bytesRead >= 0) {
bytesRead = readChannel.read(buffer);
buffer.flip();
zip.write(buffer.array(), buffer.position(), buffer.limit());
buffer.rewind();
buffer.limit(buffer.capacity());
}
} finally {
zip.closeEntry();
readChannel.close();
}
}
} finally {
zip.flush();
zip.close();
outputChannel.close();
}
}
来源：https://stackoverflow.com/questions/17871412/how-to-create-a-zip-archive-containing-google-cloud-storage-objects-within-appen