Spring Boot Executable Jar with Classpath

Question

I am building a software system to interact with an enterprise software system, using Spring Boot. My system depends on some jars and *.ini files from that enterprise system, so I cannot pack all dependencies in Maven. I would like to be able to run Spring Boot as Executable Jar with embedded Tomcat. I would also like to be able to set the classpath via the command line. So something like:

java -classpath /home/sleeper/thirdparty/lib -jar MyApp.jar

However, -classpath and -jar cannot co-exist. I have tried "-Dloader.path". It was able to load all the jar files under the folder, but not other things, like *.ini files in the folder.

So is there a way we can make -classpath to work with an Spring executable jar with embedded Tomcat?

Answer 1

If you just want add external libraries you can use the loader.path property.

java -Dloader.path="your-lib/" -jar your-app.jar

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UPDATE

If you also need to read additional files from the classpath you have to create/change the manifest file of your application.

Lets assume that your are initializing your Spring Boot context from the class de.app.Application. Your MANIFEST.MF should looks as follows:

Manifest-Version: 1.0
Main-Class: de.app.Application
Class-Path: your-lib/

And the you can simply start your app with java -Dloader.path="your-lib/" -jar MyApp.jar.

For more information about the MANIFEST.MF please see Working with Manifest Files: The Basics.

Answer 2

On Linux:

java -cp MyApp.jar:/home/sleeper/thirdparty/lib -Dloader.main=myMainApplicationClass org.springframework.boot.loader.PropertiesLauncher

On Windows:

java -cp MyApp.jar;/home/sleeper/thirdparty/lib -Dloader.main=myMainApplicationClass org.springframework.boot.loader.PropertiesLauncher

This will avoid messing with the manifest or the Spring Boot Maven plugin configuration as in the other answers. It will launch your app with the PropertiesLauncher, which allows you to specify the main class in loader.main. As mentioned earlier, for some reason if you use PropertiesLauncher with loader.path, it will not add resource files to the classpath. This works around the issue by using -cp instead of -jar.

EDIT As mentioned by Pianosaurus in the comment, use ":" instead of ";" as separator in the classpath on Linux