Runtime JDK/JRE dependency on java 17?

[puremourning]

Sorry if I missed it, but is the runtime requirement for jdt.ls written down somewhere?

It seems like it requires java 17 from a quick code inspection, whereas it previously only required java 11.

Is that right? Reason I ask is that adopt openjdk claims that 16 is the latest stable java. Anyway, would be useful to clarify what the runtime requirements are for jdt.ls.

(sorry, not an issue, but a question. I asked on mattermost, but no reply).

[fbricon]

Yes Java 17 as a minimum is now required to run, as m2e, a core jdt.ls dependency now requires Java 17 to run. However you can still compile projects back to Java 1.5

[puremourning]

OK thanks.

[dave-kennedy]

Yes Java 17 as a minimum is now required to run, as m2e, a core jdt.ls dependency now requires Java 17 to run. However you can still compile projects back to Java 1.5

Can you clarify the distinction between running and compiling? How do you use jdtls to compile? How do I use jdtls with a project that uses Java 8?

[snjeza]

How do you use jdtls to compile? How do I use jdtls with a project that uses Java 8?

What project are you using? Maven, Gradle, standard Eclipse?

[dave-kennedy]

I think I finally figured it out. The Java version used to run jdtls has to be >= 17, but the Java version used to compile the project can be configured separately. This is how it's done for nvim-jdtls:

local config = {
    cmd = {
        'java',
        '-Declipse.application=org.eclipse.jdt.ls.core.id1',
        '-Dosgi.bundles.defaultStartLevel=4',
        '-Declipse.product=org.eclipse.jdt.ls.core.product',
        '-Dlog.level=ALL',
        '-noverify',
        '-Xmx1G',
        '--add-modules=ALL-SYSTEM',
        '--add-opens', 'java.base/java.util=ALL-UNNAMED',
        '--add-opens', 'java.base/java.lang=ALL-UNNAMED',
        '-jar', '/home/dave/.jdtls/plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar',
        '-configuration', '/home/dave/.jdtls/config_linux',
        '-data', '/home/dave/.jdtls/workspaces' .. project_name
    },
    settings = {
        java = {
            configuration = {
                runtimes = {
                    {
                        name = 'JavaSE-1.8',
                        path = '/home/dave/.sdkman/candidates/java/8.0.302-open/',
                    }
                }
            }
        }
    }
}

I'm not sure how to do it outside of nvim-jdtls.

[snjeza]

@dave-kennedy You may want to take a look at Project JDKs

[dave-kennedy]

@snjeza thanks, that is helpful. Can that be set alongside configuration.runtimes or does it need to be in gradle.properties?

[snjeza]

@dave-kennedy java.configuration.runtimes

[dave-kennedy]

For the record, this is what did the trick:

local config = {
    cmd = {
        '/home/dave/.sdkman/candidates/java/18.0.2.1-open/bin/java',
        '-Declipse.application=org.eclipse.jdt.ls.core.id1',
        '-Dosgi.bundles.defaultStartLevel=4',
        '-Declipse.product=org.eclipse.jdt.ls.core.product',
        '-Dlog.level=ALL',
        '-noverify',
        '-Xmx1G',
        '--add-modules=ALL-SYSTEM',
        '--add-opens', 'java.base/java.util=ALL-UNNAMED',
        '--add-opens', 'java.base/java.lang=ALL-UNNAMED',
        '-jar', '/home/dave/.jdtls/plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar',
        '-configuration', '/home/dave/.jdtls/config_linux',
        '-data', '/home/dave/.jdtls/workspaces/' .. project_name
    },
    settings = {
        java = {
            configuration = {
                runtimes = {
                    {
                        name = 'JavaSE-1.8',
                        path = '/home/dave/.sdkman/candidates/java/8.0.302-open/',
                        default = true
                    },
                    {
                        name = 'JavaSE-18',
                        path = '/home/dave/.sdkman/candidates/java/18.0.2.1-open/'
                    }
                }
            },
            import = {
                gradle = {
                    home = '/home/dave/.sdkman/candidates/java/8.0.302-open/'
                }
            }
        }
    }
}

Except now none of my libs aren importing but that's another issue.