Improve diagnostics when JVM launched by spring-boot:run exits with a non-zero status

[drahkrub]

If a forked spring boot app finishes with exitCode != 0 && exitCode != EXIT_CODE_SIGINT
a MojoExecutionException is thrown with the message "Application finished with exit code: " + exitCode.
This Exception is than catched by the surrounding try-catch and used as cause in a rethrown MojoExecutionException with the misleading/wrong message "Could not exec java".

So the initial thrown Exception is not "silently swallowed" but it is "hidden" as the root cause of the second Exception which exposes a misleading/wrong message.

This happened to me right when starting my spring boot app (had some problem in an ApplicationContextInitializer which was caused due to the problems described in #16819 - my app starts without problems in a non forked VM or when starting the JAR file), so my first thought was that something is wrong with my environment or java installation causing spring boot`s inability to "exec java" - took me quite some time.

Therefore optimizing the exception handling in this place (RunMojo#runWithForkedJvm(...)) would be nice (i.e. more specific error message in first place).

P.S.: Sorry for raising another issue but I'm afraid of creating more off-topic follow-up questions as in #16811 ;-)

[philwebb]

I think it would be safe to change this catch to rethrow any MojoException without wrapping.