Google App Engine中的Google云存储文件位置

Question

I have used below code to write something to my file google cloud storage.

FileService fileService = FileServiceFactory.getFileService();
    GSFileOptionsBuilder optionsBuilder = new GSFileOptionsBuilder()
       .setBucket(BUCKETNAME)
       .setKey(FILENAME)
       .setMimeType("text/html")
       .setAcl("public_read")
       .addUserMetadata("myfield1", "my field value");
    AppEngineFile writableFile =
         fileService.createNewGSFile(optionsBuilder.build());
    // Open a channel to write to it
     boolean lock = false;
     FileWriteChannel writeChannel =
         fileService.openWriteChannel(writableFile, lock);
     // Different standard Java ways of writing to the channel
     // are possible. Here we use a PrintWriter:
     PrintWriter out = new PrintWriter(Channels.newWriter(writeChannel, "UTF8"));
     out.println("The woods are lovely dark and deep.");
     out.println("But I have promises to keep.");
     // Close without finalizing and save the file path for writing later
     out.close();
     String path = writableFile.getFullPath();
     // Write more to the file in a separate request:
     writableFile = new AppEngineFile(path);
     // Lock the file because we intend to finalize it and
     // no one else should be able to edit it
     lock = true;
     writeChannel = fileService.openWriteChannel(writableFile, lock);
     // This time we write to the channel directly
     writeChannel.write(ByteBuffer.wrap
               ("And miles to go before I sleep.".getBytes()));

     // Now finalize
     writeChannel.closeFinally();
     resp.getWriter().println("Done writing...");

     // At this point, the file is visible in App Engine as:
     // "/gs/BUCKETNAME/FILENAME"
     // and to anybody on the Internet through Cloud Storage as:
     // (http://storage.googleapis.com/BUCKETNAME/FILENAME)
     // We can now read the file through the API:
     String filename = "/gs/" + BUCKETNAME + "/" + FILENAME;
     AppEngineFile readableFile = new AppEngineFile(filename);
     FileReadChannel readChannel =
         fileService.openReadChannel(readableFile, false);
     // Again, different standard Java ways of reading from the channel.
     BufferedReader reader =
             new BufferedReader(Channels.newReader(readChannel, "UTF8"));
     String line = reader.readLine();
     resp.getWriter().println("READ:" + line);

    // line = "The woods are lovely, dark, and deep."
     readChannel.close();

It seems it's writing and then reading, but when I check in the cloud storage area (using firefox), the file hasn't been edited. Any idea?

Answer 1

Is this in the production or development environment?

When you're using the dev server writes to Google Storage are simulate and are not written to a real bucket.

Answer 2

There could be two problems.

1. You could forget to add permissions to your bucket. Check https://developers.google.com/appengine/docs/java/googlestorage/overview#Prerequisites how to do it.

2. You are trying to update the file. After writeChannel.closeFinally() the file becomes read-only. You can not change/update/append to it.