Even if a java program doesn't get deployed to a server, we usually just run it right from inside Eclipse, NetBeans, IntelliJ, or what-have-you since its usually to debug something, or is a college programming assignment. So the need to spruce up a Java program to be easily called from the command line just doesn't come up very often. Some may argue this is for the better since java programs have that short start-up delay when kicking up a new jvm instance. I'm not here to argue on that point however.
Let's talk about a specific point of time in your java project's lifecycle, where you decide it is getting too annoying for you or your clients to start up your java program using:
java -jar awesome.jar
You may even be using properties as a cheap-n-easy way to do arguments:
java -jar awesome.jar -DmakeStuffWork=true -Dname="Bob Newhart"
If it is to run on the terminal or in a window, there will come a time when you wish you could just have the program behave like every other executable on the computer. I found myself in this very situation when I was creating lsdup, a command-line tool to list duplicate files. It needed to be able to run elegantly enough that the people using it didn't need to know or care about Java. The only requirement was that the users had an installed Java VM.
I was able to convert from "java -jar lsdup.jar" to just "lsdup.exe" on Windows by wrapping the jar in a different tool which is essentially a very small executable (or even script), called Launch4J. In Linux land, I used bash scripts (which should also work in principle on Mac OS X, though I've not tested it) to convert it to "./lsdup.sh".
For the command-line options, I used Apache Commons CLI to grab all the input.
Of course, this all works with Maven. As always, Stack Overflow has the answer for working with Launch4J targets. You can also run the bash scripts mentioned above in maven as well.
The not-so-obvious part is that while it would have been nice to cross-compile (or cross-wrap, in this case) the build so that I could create the Launch4J Windows exe wrapper in Linux in addition to creating the shell script, or conversely create the shell script in Windows in addition to creating the exe. Laziness got the best of me and I did not figure out how to do it.
What I ended with was a maven script with two profiles: one which builds the shell script when on Linux, and one which builds the Windows exe when on Windows:
<profiles>
<profile>
<id>posix</id>
<activation>
<os>
<family>!Windows</family>
</os>
</activation>
<build>
<!-- The maven code to execute the shell script (linked above) goes here. -->
</build>
</profile>
<profile>
<id>windows</id>
<activation>
<os>
<family>Windows</family>
</os>
</activation>
<build>
<!-- The maven code to wrap Launch4J around the jar (linked above) goes here. -->
</build>
</profile>
</profiles>
This worked well for me, and I will consider it in the future should I ever need to create another Java program to behave like any other executable file.
