kickstart.nvim/ftplugin/java.lua

local home = os.getenv('HOME')
local jdtls = require('jdtls')

-- File types that signify a Java project's root directory. This will be
-- used by eclipse to determine what constitutes a workspace
local root_markers = { 'gradlew', 'mvnw', '.git' }
local root_dir = require('jdtls.setup').find_root(root_markers)

-- eclipse.jdt.ls stores project specific data within a folder. If you are working
-- with multiple different projects, each project must use a dedicated data directory.
-- This variable is used to configure eclipse to use the directory name of the
-- current project found using the root_marker as the folder for project specific data.
local workspace_folder = home .. "/.local/share/nvim/eclipse/" .. vim.fn.fnamemodify(root_dir, ":p:h:t")

-- Helper function for creating keymaps
function nnoremap(rhs, lhs, bufopts, desc)
  bufopts.desc = desc
  vim.keymap.set("n", rhs, lhs, bufopts)
end

local config = {
  flags = {
    debounce_text_changes = 80,
  },
  on_attach = on_attach, -- We pass our on_attach keybindings to the configuration map
  root_dir = root_dir,   -- Set the root directory to our found root_marker
  -- Here you can configure eclipse.jdt.ls specific settings
  -- These are defined by the eclipse.jdt.ls project and will be passed to eclipse when starting.
  -- 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 = {
      format = {
        settings = {
          -- Use Google Java style guidelines for formatting
          -- To use, make sure to download the file from https://github.com/google/styleguide/blob/gh-pages/eclipse-java-google-style.xml
          -- and place it in the ~/.local/share/eclipse directory
          url = home .. ".local/share/nvim/eclipse/eclipse-java-google-style.xml",
          profile = "GoogleStyle",
        },
      },
      signatureHelp = { enabled = true },
      contentProvider = { preferred = 'fernflower' }, -- Use fernflower to decompile library code
      -- Specify any completion options
      completion = {
        favoriteStaticMembers = {
          "org.hamcrest.MatcherAssert.assertThat",
          "org.hamcrest.Matchers.*",
          "org.hamcrest.CoreMatchers.*",
          "org.junit.jupiter.api.Assertions.*",
          "java.util.Objects.requireNonNull",
          "java.util.Objects.requireNonNullElse",
          "org.mockito.Mockito.*"
        },
        filteredTypes = {
          "com.sun.*",
          "io.micrometer.shaded.*",
          "java.awt.*",
          "jdk.*", "sun.*",
        },
      },
      -- Specify any options for organizing imports
      sources = {
        organizeImports = {
          starThreshold = 9999,
          staticStarThreshold = 9999,
        },
      },
      -- How code generation should act
      codeGeneration = {
        toString = {
          template = "${object.className}{${member.name()}=${member.value}, ${otherMembers}}"
        },
        hashCodeEquals = {
          useJava7Objects = true,
        },
        useBlocks = true,
      },
      -- If you are developing in projects with different Java versions, you need
      -- to tell eclipse.jdt.ls to use the location of the JDK for your Java version
      -- See https://github.com/eclipse/eclipse.jdt.ls/wiki/Running-the-JAVA-LS-server-from-the-command-line#initialize-request
      -- And search for `interface RuntimeOption`
      -- The `name` is NOT arbitrary, but must match one of the elements from `enum ExecutionEnvironment` in the link above
      configuration = {
        runtimes = {
          {
            name = "JavaSE-17",
            path = home .. "/.jkds/corretto-17.0.6",
          },
        }
      }
    }
  },
  -- cmd is the command that starts the language server. Whatever is placed
  -- here is what is passed to the command line to execute jdtls.
  -- Note that eclipse.jdt.ls must be started with a Java version of 17 or higher
  -- See: https://github.com/eclipse/eclipse.jdt.ls#running-from-the-command-line
  -- for the full list of options
  cmd = {
    'java',
    '-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',
    '-Xmx4g',
    '--add-modules=ALL-SYSTEM',
    '--add-opens', 'java.base/java.util=ALL-UNNAMED',
    '--add-opens', 'java.base/java.lang=ALL-UNNAMED',
    -- If you use lombok, download the lombok jar and place it in ~/.local/share/eclipse
    '-javaagent:' .. home .. '/.local/share/nvim/mason/plugins/jdtls/lombok.jar',

    -- The jar file is located where jdtls was installed. This will need to be updated
    -- to the location where you installed jdtls
    '-jar',
    vim.fn.glob(home ..
      '.local/share/nvim/mason/packages/jdtls/plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar'),

    -- The configuration for jdtls is also placed where jdtls was installed. This will
    -- need to be updated depending on your environment
    '-configuration', home .. '.local/share/nvim/mason/packages/jdtls/config_linux',

    -- Use the workspace_folder defined above to store data for this project
    '-data', workspace_folder,
  },
}

-- Finally, start jdtls. This will run the language server using the configuration we specified,
-- setup the keymappings, and attach the LSP client to the current buffer
jdtls.start_or_attach(config)