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I have a Java project in Eclipse. It works fine and I can run it from cmd using java -jar sample-app.jar

I now have to use Gradle to produce an executable sh file for use in Linux. I've found some resources on creating start scripts but the most I've managed to do is use the standard 'startScripts' task to create a sample.app.bat file.

I've scoured question after question and page after page on google to try and find an answer and I'm not having much luck. I've also read through the Gradle Application plugin documentation a number of times and still quite confused.

How do I write a Gradle task to generate an sh file to execute my sample-app.jar file?

Note: The sample-app.bat file does no execute. It only produces an "Error: Cannot find or load main class com.sample.MainClass

Opal
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2 Answers2

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It seems that mentioned application plugin is what you're looking for. Here you can find a little demo. Now to run main class you need to run gradle run. To prepare sh and bat scripts run gradle gradle startScripts. To prepare a runnable (and easily copyable) version of application and starts scripts run gradle distZip or gradle distTar. Both tasks will prepare and archive that can be extracted to given directory and run with prepared script. The last task gradle installDist will prepare both script and executable jar in a given directory but without packing them.

All artifacts created with dist*, installDist and startScripts can be found under build directory. Try running:

gradle clean distZip distTar installDist

and then tree -a build to view all prepared filed.

To run main class from the prepared jar remember to execute shell scripts in the correct directory, e.g.: build/install/lol/bin.

Opal
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  • Thank you. I was creating the execution script the whole time, just wasn't aware that I was doing it. Your answer has certainly helped clear up my confusion. Greatly appreciated! –  Jan 18 '17 at 23:41
  • I'm now finding that all of my applications cannot be executed using the generated batch file. It was working this morning when i initially replied, now they were not. No changes to the code have been made since. I'm getting the error; Error: Could not find or load main class com.example.Main –  Jan 19 '17 at 05:14
  • @Afterfield I guess it all runs correctly - have you configured main class? Also, please remember that you need to run the script from the valid location. – Opal Jan 19 '17 at 09:05
  • Turns out I completely misunderstood which files were being built. I was trying to execute the project files created by Gradle, not the ones compiled and zipped for distribution. This was causing a number of errors regarding not being able to find classes and libraries, despite everything being configured correctly. Running the execution scripts from the .zip file works perfectly and I've had no problems since. –  Jan 20 '17 at 10:02
  • @Opal is the similar functionality, I mean creating binaries is available in `maven` world – Kasun Siyambalapitiya Jul 03 '17 at 03:53
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There is a standard Gradle way how to do it. You must start your gradle.build by 

apply plugin: 'application'

After that, you can launch distTar, distZip, and installZip tasks. (They lie in distribution task folder). Each of them creates the build/scripts folder in your project and puts windows and Linux scripts there. Also, they create tar/zip/folder installation - look at the distribution plugin.

Notice, you don't need to apply the distribution plugin - it is in the 'application' plugin already. And the startScripts plugin is in the distribution plugin.

But the situation is not so nice. The second problem is that the generated scripts are bad. At least that for Windows. So, you will have to edit them by hand or automate the process in the script inserted in startScripts. It will look so:

startScripts {
    doLast {
         your script editing lines here. 
    }
}
Gangnus
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