Directory sync

This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. It does not describe an actual complete program. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; I have too many other projects of my own.

I do contract work for a living, which could include writing a program such as this. However, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project any way you please.

This is a simple project. It requires almost no user interface. The code can be cannibalised from various code posted on this website. It works like this:

The source and target directories might be on the same machine or on two different machine connected on a LAN. Your program makes sure the target directory is identical to the source directory doing as necessary:

copying files
creating subdirectories
changing capitalisation to match the source.
changing file attributes to match the source.
changing file data to match the source.
deleting files in the target directory tree not in the source directory tree.
deleting directories in the target directory that no longer exist in the source tree.

To copy files use FileTransfer. To traverse directory trees, use Batik. You will need to write a little JNI to detect and set the Windows file attributes (or other platform) Use FileTimes as a base. You might be able to get around that problem by using zip files for transport which might automatically transfer the attribute bits.

There are many other directory sync programs, but they are too complicated and suffer from featuritis.

Extensions:

A version of this program that does not delete any files in the target directory tree. You might call it Propagate.
When the source and target are on different machines, compress the changes and send them as a single big zip. For this approach to make sense, you have a tricky problem to solve, how to spawn a task on the other computer.
A version that uses FTP to ensure a directory on server matches the one on the desktop.
Note that the Replicator will propagate a directory tree to many machines via an HTTP server.
Add a GUI to let you define multiple directory trees.
A two way sync, so that both directories end up identical. You take the more recent file on either side as the master, with a warning if the newer file is smaller. You might call this program Sync.

AllWaysync: prissy, frets over all caps files, and fails when it needlessly builds intermediate temporary directories
GoodSync: free to non-profits. Overly complicated
Smart FTP project
the Replicator

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