springboot Print the java version being used on startup

Hi,

this PR closes #21553 by using System.getProperty("java.version"). Alternatively, we could check for Runtime.version() being available (which is the case for JDK 9+) and use that.

Cheers, Christoph

Comment From: wilkinsona

Thanks for the PR, @dreis2211. Here's what's logged by StartupInfoLoggerTests#sourceClassIncluded with the proposed changes:

Starting StartupInfoLoggerTests on fulcrum.local with PID 42978 (started by awilkinson in /Users/awilkinson/dev/spring-projects/spring-boot/master/spring-boot-project/spring-boot) on Java 1.8.0_252

I wonder if the Java version should appear earlier in the message. I also wonder about the two uses of on, one to refer to the host and the other to the JVM.

What do you think of something like the following:

Starting StartupInfoLoggerTests using Java 1.8.0_252 on fulcrum.local with PID 42978 (started by awilkinson in /Users/awilkinson/dev/spring-projects/spring-boot/master/spring-boot-project/spring-boot)

Comment From: dreis2211

Funny enough, I had a similar version before (with with instead of using but hey) and I too find the double on sub-optimal. I decided to append it at the end to less likely break it for anyone parsing this log statement - (I've seen people do this for startup statistics).

I'm totally fine with what you suggested. Let me know if I should change it.

Comment From: wilkinsona

@dreis2211 Thanks. Given that this will go into 2.4, I'm comfortable with the small risk of breaking someone's log message parsing. It's an easy one for them to correct and we don't make any guarantees about the structure of any of our messages.

I have a slight preference for using rather than with to avoid duplicating the with in with PID ….