Metals compiled with a more recent version of Java Runtime

[suzhiking]

Hi, I'm trying to setup Scala uses older version of Java. When I downloaded coursier and run MetalsInstall, it prompts

[ERROR][2025-01-07 14:27:43] .../vim/lsp/rpc.lua:770	"rpc"	"/Users/zhisuw/.cache/nvim/nvim-metals/metals"	
"stderr"	"java.lang.UnsupportedClassVersionError: scala/meta/metals/Main has been compiled by a more recent version
of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
java.base/java.lang.ClassLoader.defineClass1(Native Method)
java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1017) 
java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174) 
java.base/java.net.URLClassLoader.defineClass(URLClassLoader.java:555)
java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:458)
java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:452)
java.base/java.security.AccessController.doPrivileged(Native Method) java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:451)
java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589)
java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
coursier.bootstrap.launcher.a.a(Unknown Source)
coursier.bootstrap.launcher.Launcher.main(Unknown Source)"

I've already set JAVA_HOME correctly. Anyone know how to resolve this?

opts = function()
	local metals_config = require("metals").bare_config()
        metals_config.settings = {
              javaHome = "path/to/jdk11/home"
        }
	metals_config.on_attach = function(client, bufnr)
		-- your on_attach function
	end

	return metals_config
end,

[ckipp01]

I know this is really late, but the javaHome you have set here runs your project, not Metals. Locally you need to be using Java 17 for Metals to work as expected.

[itsjef]

I ran into the same problem. My project required JRE 11 and Scala 2.12.17. It turned out Metals 1.3.5 was the last version supporting JRE 11

Here is how I resolved it:

1. Install metals 1.3.5 with coursier: cs install metals:1.3.5. Make sure the executable in $PATH points to this version
2. (optional) Remove existing metals executable installed by nvim-metals. Mine were $HOME/.cache/nvim/nvim-metals/metals
3. Set useGlobalExecutable = true in metals_config.settings (link) to use the v1.3.5 executable above. By default, nvim-metals would install the latest stable version of metals (currently 1.6.x) which no longer supports JRE 11