Help reading transaction logs

[Andy Stewart]

Can anybody help with how to read a transaction log written by derby in 
a jar?

I think the log consists of serialised Loggable objects and am trying to 
use the derby class files to read it back in. However when I point it at 
a transaction log (which is about 1mb big) I am not able to read any 
objects back.

The program I have got looks like:

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;

import org.apache.derby.iapi.services.io.FormatIdInputStream;

public class LogReader {

   private String logFileName;

   /**
    * @param args
    */
   public static void main( String[] args ) throws Exception {
       LogReader logReader = new LogReader( "C:\\Documents and 
Settings\\andy.stewart\\workspace_trunk\\DerbyInAJar\\derbyDB\\log\\log1.dat" 
);
       logReader.readLogFile();
   }

   public LogReader( String logFileName ) {
       this.logFileName = logFileName;
   }

   public void readLogFile() throws Exception {
       File file = new File( this.logFileName );
       System.out.println( "File exists: " + file.exists() );
       InputStream fileInputStream = new FileInputStream( file );
       FormatIdInputStream formatIdInputStream = new 
FormatIdInputStream(fileInputStream);
       Object object = formatIdInputStream.readObject();
      
       System.out.println(object);
   }
}

The output is as follows:
   File exists: true
   null

Could anybody shed any light on what I should be doing to read these 
logs files in?

Thanks,
Andy