VSCode extension JDK version

[rubensa]

Installed version

• Spring Boot Extension Pack v0.0.8
• Spring Boot Dashboard v0.2.0
• Spring Boot Tools v1.25.0
• Spring Initializr Java Support v0.7.0

Looks like some code in the latest version is compiled against Java 11 (but prerequisites is JDK 8)

Activating 'vscode-spring-boot' extension
Found java exe: /opt/sdkman/candidates/java/8.0.282.hs-adpt/bin/java
isJavaEightOrHigher => true
Redirecting server logs to /dev/null
ERR: Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/springframework/ide/vscode/boot/app/BootLanguagServerBootApp has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:756)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:601)

Also reported here: microsoft/vscode-spring-boot-dashboard#125

[rubensa]

As a side note, I have configured the "spring-boot.ls.java.home" setting to point to the desired JDK (verison 8).

[Eskibear]

I can repro it. I've installed both JDK 11 and 8 on my machine.

By default. it works well, and logs are:

Activating 'vscode-spring-boot' extension
Found java exe: C:\Users\zy199\AppData\Local\Programs\AdoptOpenJDK\jdk-11.0.8.10-hotspot\bin\java.exe
isJavaEightOrHigher => true
Redirecting server logs to /dev/null
ERR: Disabling server log output. No more output will be sent after this.
Child process connected on port 45556

If I point "spring-boot.ls.java.home" to JDK 8, and reload window, below error occurs, same as above

Activating 'vscode-spring-boot' extension
Found java exe: C:\Program Files\Java\jdk1.8.0_281\bin\java.exe
isJavaEightOrHigher => true
Redirecting server logs to /dev/null
ERR: Error: A JNI error 
ERR: has occurred, please check your installation and try again
Exception in thread "main" 
ERR: java.lang.UnsupportedClassVersionError: org/springframework/ide/vscode/boot/app/BootLanguagServerBootApp has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

So I believe those who has only JDK 8 installed will have the same issue.

[martinlippert]

Yes, the extension now requires a JDK11 to run on and the internal check should be updated to reflect that.
@BoykoAlex Can you have a look and update the internal check to look for a JDK11 (and while doing that, we can also probably remove all the checks looking for tools.jar, since that check isn't been used when running on an JDK >=9 anyway).

[martinlippert]

So to quickly fix this, change the settings via "spring-boot.ls.java.home" to point to a JDK >= 11.

[rubensa]

One question here...
The extension needs JDK >= 11 to work but how does Spring Boot Dashboard launch my application? Can I make sure that my code is being run with the JDK I'm supposed to be developing to (in this case JDK 8)?

As far as I know, the Language Support for Java extension knows the Java runtimes I have installed via "java.configuration.runtimes" config setting, and uses the "best match" based on this and "java.version" (if you are using Spring Boot or "maven.compiler.source", or "maven.compiler.release", depending on maven-compiler-plugin version) maven property to decide witch runtime to use for the compilation.
Does Spring Boot Dashboard extension the same to decide witch java runtime use to launch de application?

[kdvolder]

@rubensa about your question...

TLDR; Setting spring-boot.ls.java.home doesn't change how your project launches. It only the affects STS language server. So it should be fine for your scenario.

More detailed explanation. It should be possible to control Java home for your project and for the redhat java tooling (which is what the boot dashboard uses to launch your project) independently. The jvm used to launch the sts4 extensions are controlled by spring-boot.ls.java.home configuration key in vscode settings.json. The redhat tooling is configured independently via java.home.

I was also expecting that you should be able to control the Java home for a specific launch as well from it's launch.json file, but googling a bit for the documentation on this I could only find the list of launch.json option here and it makes no mention of how you set the Java home: https://code.visualstudio.com/docs/java/java-debugging#_configuration-options

That could be an oversight since just like for STS4, the JVM required to launch redhat Java tooling may not neccessarily be the one that a user wants to launch their own project with.

Anyway assuming that doc I found is complete, I think you'd have to control the jvm used for launching your project using 'java.home' property in user/workspace settings while spring-boot.ls.java.home controls only the JVM used to launch STS extension's language server.