How to build JAR files dynamically

Question

I'm making a program that needs to be able to let Clients change a setting, and using what I'm calling a "Builder", create a .jar that replaces some constants in a class with their settings.

In other words, I have a GUI that has a few textfields so that when they press the JButton labeled Build, it creates a new Runnable Jar that in a Constants class whose settings are changed with what was in the textfields.

Is this possible? I've heard about ANT Scripts, but I'm not really sure if that's what I'm looking for here.

Thanks

Answer 1

have you considered using a .properties files or something similar instead? You can use ant scripts for what you are describing (check out http://ant.apache.org/manual/Tasks/replaceregexp.html , you could use this task in your build.xml to dynamically change the .java files but it seems a little kludgy) but it might not be the best solution.

Check this page: http://www.mkyong.com/java/java-properties-file-examples/ which has some detail about saving to/loading from a properties file. You could set up your constants class to load it's state variables from this file, and set up the Build JButton to create that properties file.

I'm trying to think of a use case where you would want to modify the class source itself rather than use a properties file, but to be honest I can't. So I suppose you may have some special circumstance where this is not a tenable solution for you, but 99% of the time this is how I would suggest you go about it.