如何在appengine java应用程序中创建包含Google云存储对象的zip存档？ [英] How to create a zip archive containing google cloud storage objects within appengine java app?

问题描述

假设我有50个对象（每个15Mb）存储在Google云端存储中。现在我需要创建一个包含所有这些文件的zip文件，并将结果文件存储回GCS。
我该如何从appengine的java应用程序中做到这一点？

解决方案

我写了下面的方法似乎是工作正常。

  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。）; 
继续; 
} 
 // 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（）; 
} 
} 
}最后{
 zip.flush（）; 
 zip.close（）; 
 outputChannel.close（）; 
} 
} 
  

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?

解决方案

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();
    }
}

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