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Some libraries and applications rely on a RandomAccessFile instance to process its IO tasks, and thus are usually limited to access data from a local file.
If an application needs to access data from another source (from an SFTP file, an HTTP file, CIFS-accessible file, a file inside a zip, tar, gzip or bzip2 archive, etc), it has to use another algorithm - the process isn’t transparent.

Such application could be benefited by an adapter class providing a “RandomAccessFile” view of arbitrary data sources, allowing it to transparently access data from different sources.

Example: a database server using a RandomAccessFile instance to access its data from a local file would automatically be able to access it from a gzip-compressed file.

RACRandomAccessFile is such an adapter class; by leveraging Commons-VFS and the file systems it provides, it allows you to use any RandomAccessContent instance as if it were a RandomAccessFile instance.

And it’s easy to use. See the usage example below:

public class TestRandomAccessFileClass {

public static void main(String[] args) {

try {
// This example reads data from a file using HTTP,
// but any <a onclick="javascript:urchinTracker ('/outgoing/jakarta.apache.org/commons/vfs/filesystems.html');"  href="http://jakarta.apache.org/commons/vfs/filesystems.html">VFS-supported file system</a> could have been used.

RandomAccessFile raf = getRandomAccessFile(”http://my.server.com/path/to/file.dat”);</code>

// Do something with raf
raf.seek(128);
byte[] buf = new byte[5];
raf.read(buf);
raf.close();

} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}

}

}

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import java.io.IOException;
import java.io.RandomAccessFile;

import org.apache.commons.vfs.FileObject;
import org.apache.commons.vfs.FileSystemManager;
import org.apache.commons.vfs.RACRandomAccessFile;
import org.apache.commons.vfs.RandomAccessContent;
import org.apache.commons.vfs.VFS;
import org.apache.commons.vfs.util.RandomAccessMode;

public class VFSKit {

public static RandomAccessFile getRandomAccessFile(String name)
throws IOException {

FileSystemManager mgr = VFS.getManager();
FileObject file = mgr.resolveFile(name);
RandomAccessContent rac = file.getContent().<a onclick="javascript:urchinTracker ('/outgoing/jakarta.apache.org/commons/vfs/apidocs/org/apache/commons/vfs/FileContent.html#getRandomAccessContent%28org.apache.commons.vfs.util.RandomAccessMode%29');"  href="http://jakarta.apache.org/commons/vfs/apidocs/org/apache/commons/vfs/FileContent.html#getRandomAccessContent%28org.apache.commons.vfs.util.RandomAccessMode%29">getRandomAccessContent</a>(
RandomAccessMode.READ);

RandomAccessFile raf = new RACRandomAccessFile(rac);</code>

return raf;

}

}