Copy files within JAR to disk

[Jos Vermeulen]

Hi. I'm a novice trying to learn some Java. Currently working on a small application. A feature in my application is that it holds some files (resources) and copies it to the hard disk.

Running it from Eclipse, it works 100% fine (!!). Unfortunately, when I export my app to a JAR and run it, files from within my application that need to be copied to the hard disk, aren't getting copied...

Here's some code that handles the copying from jar to hard disk:

File srcFile = new File(this.getClass().getResource("/srcFile.txt").toURI());
File tgtFile = new File("C:\\tgtFile.txt");
FileChannel sourceChannel = new FileInputStream(myFile).getChannel();
FileChannel targetChannel = new FileOutputStream(tgtFile).getChannel();
sourceChannel.transferTo(0, sourceChannel.size(), targetChannel);
sourceChannel.close();
targetChannel.close();

I'm pretty sure the problem lies in the this.getClass().getResource() part. But not sure on what to fix.

There's probably more efficient code for copying files, but I only need a 'quick fix' for now. Can someone please help me?

[Campbell Ritchie]

Don't know. Why are you not using simpler classes? For text files you can use Scanner and Formatter.

That looks too difficult for "beginning Java", so I shall move the discussion.

And welcome to JavaRanch

[Rob Spoor]

You can't use java.io.File, java.io.FileInputStream, java.io.FileOutputStream, java.io.FileReader, java.io.FileWriter and java.nio.channels.FileChannel with files inside JAR files. That's because technically speaking they are no longer files - they are JAR file entries. You should switch to Class.getResourceAsStream() instead, then use old fashioned stream-based copying.