在JAR中写入属性文件

Question

I'm create an application that is going to be run on Windows, Mac OX and Linux. I have a properties file storing user settings which need to be read and changed on the fly.

A JAR file is compressed and is not meant to be changed on the fly which means I should write to an external file.

I'm using :

new FileInputStream("database")

new FileOutputStream("database")

How do I create a URL which is going to be consistent throughout all three operating systems. The JAR is run as an application on the desktop and I would like the file to be stored somewhere discrete.

I've tried reading from a local file in the same package as this class :

this.getClass().getResourceAsStream("database")

This works however I can't seem to create an output stream to write to the same file but this would be breaking the rule of changing a JAR file on the fly.

Answer 1

There are plenty of good reasons for which you should not do this, off the top of my head:

• GetResourceAsStream does not necessarily get the file from the JAR itself. You coincidentally got it from there because the Jar was the first or the only element in the class path.
• Writing a file in your own Jar could break the JAR signature if you are going to sign it.
• The database could need to be backed up; in this case you may want to back it up separate from the code (the code could be upgraded when restoring the database).

Hope this helps.