Writing GZIP file with nio

问题

This is my code:

WritableByteChannel channel = null;
GZIPOutputStream out = null;
try {
     channel = Channels.newChannel(new FileOutputStream("C:\\temp\\111.zip"));

     out = new GZIPOutputStream(Channels.newOutputStream(channel));
    for (long i = 0; i < 10000000000; i++) {    
       out.write(("string" + i + "\n").getBytes());
     } 

   } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            if (channel != null) {
                channel.close();
            }
        } catch (Exception e) {
        }
        try {
            if (out != null) {
                out.close();
            }
        } catch (Exception e) {
        }
    }    }

I get zip but it's contents is damaged.

回答1:

Why are you saving it as zip if you're using a gzip stream? Use .gz as the extension.

Edit
Assuming that it's not the .zip extension at fault here (it's still bad though):

You should probably consider calling out.finish() before closing it.
I'm pretty sure you don't need all the channel stuff. You can simply pass the FileOutputStream to GZIPOutputStream

回答2:

I would do:

GZIPOutputStream gzipOS = new GZIPOutputStream(new FileOutputStream("C:\\temp\\111.gz"));
WritableByteChannel out = Channels.newChannel(gzipOS);

And simply use out.write() to write using NIO. Don't forget to close resources later.

回答3:

When you call out.close() it will close the underlying stream/channel as well.

If you close the underlying channel first any buffered data or footer cannot be written.

The GZIP format contains a CRC32 which must be at the end, cannot be written until you clsoe the stream and I expect this is missing so the file contents cannot be validated. The simplest solution is to not close the underlying channel yourself.

BTW: As a rule it is usually best to close resources in the reverse order they were created. ;)

来源：https://stackoverflow.com/questions/9394098/writing-gzip-file-with-nio

标签

java

gzip

nio