java cannot be resolved using nvim-jdtls

[pogopaule]

Before nvim-jdtls I used jdt.ls via mason.nvim. There everything worked fine. However I would like to switch to nvim-jdtls for its larger feature set and dap integration.

But I struggle to debug the following problem:

Neither any of the java.* packages can be resolved nor Classes like String or even Object. Classes from third party libs are no problem.

My config

local config = {

  -- The command that starts the language server
  -- See: https://github.com/eclipse/eclipse.jdt.ls#running-from-the-command-line
  cmd = {

    'java', -- or '/path/to/java17_or_newer/bin/java'
            -- depends on if `java` is in your $PATH env variable and if it points to the right version.

    '-Declipse.application=org.eclipse.jdt.ls.core.id1',
    '-Dosgi.bundles.defaultStartLevel=4',
    '-Declipse.product=org.eclipse.jdt.ls.core.product',
    '-Dlog.protocol=true',
    '-Dlog.level=ALL',
    '-Xms1g',
    '--add-modules=ALL-SYSTEM',
    '--add-opens', 'java.base/java.util=ALL-UNNAMED',
    '--add-opens', 'java.base/java.lang=ALL-UNNAMED',

    '-jar', '/home/pogopaule/opt/jdt-language-server-1.9.0-202203031534/plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar',
         -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^                                       ^^^^^^^^^^^^^^
         -- Must point to the                                                     Change this to
         -- eclipse.jdt.ls installation                                           the actual version


    '-configuration', '/home/pogopaule/opt/jdt-language-server-1.9.0-202203031534/config_linux',
                    -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^        ^^^^^^
                    -- Must point to the                      Change to one of `linux`, `win` or `mac`
                    -- eclipse.jdt.ls installation            Depending on your system.


    -- See `data directory configuration` section in the README
    '-data', workspace_dir
  },

  -- 💀
  -- This is the default if not provided, you can remove it. Or adjust as needed.
  -- One dedicated LSP server & client will be started per unique root_dir
  root_dir = require('jdtls.setup').find_root({'.git', 'mvnw', 'gradlew'}),

  -- Here you can configure eclipse.jdt.ls specific settings
  -- See https://github.com/eclipse/eclipse.jdt.ls/wiki/Running-the-JAVA-LS-server-from-the-command-line#initialize-request
  -- for a list of options
  settings = {
    java = {
    }
  },

  -- Language server `initializationOptions`
  -- You need to extend the `bundles` with paths to jar files
  -- if you want to use additional eclipse.jdt.ls plugins.
  --
  -- See https://github.com/mfussenegger/nvim-jdtls#java-debug-installation
  --
  -- If you don't plan on using the debugger or other eclipse.jdt.ls plugins you can remove this
  init_options = {
    bundles = {}
  },
}

The troubleshooting section didn't help. I tried various Java projects. All of them were gradle projects. I also tested it with a newly initialized gradle hello world project.

Java is installed via asdf.

And again, the same projects work fine with jdt.ls installed and integrated via mason.nvim.

[pogopaule]

Fixed it by setting my settings to

  settings = {
    java = {
      configuration = {
        runtimes = {
          {
            name = 'JavaSE-18',
            path = '/home/pogopaule/.asdf/installs/java/adoptopenjdk-18.0.2+9/',
          },
        }
      }
    }
  },