nvim/pack/acp/start/nvim-lspconfig/lua/lspconfig/server_configurations/jdtls.lua

local util = require 'lspconfig.util'
local handlers = require 'vim.lsp.handlers'

local env = {
  HOME = vim.loop.os_homedir(),
  XDG_CACHE_HOME = os.getenv 'XDG_CACHE_HOME',
  JDTLS_JVM_ARGS = os.getenv 'JDTLS_JVM_ARGS',
}

local function get_cache_dir()
  return env.XDG_CACHE_HOME and env.XDG_CACHE_HOME or util.path.join(env.HOME, '.cache')
end

local function get_jdtls_cache_dir()
  return util.path.join(get_cache_dir(), 'jdtls')
end

local function get_jdtls_config_dir()
  return util.path.join(get_jdtls_cache_dir(), 'config')
end

local function get_jdtls_workspace_dir()
  return util.path.join(get_jdtls_cache_dir(), 'workspace')
end

local function get_jdtls_jvm_args()
  local args = {}
  for a in string.gmatch((env.JDTLS_JVM_ARGS or ''), '%S+') do
    local arg = string.format('--jvm-arg=%s', a)
    table.insert(args, arg)
  end
  return unpack(args)
end

-- TextDocument version is reported as 0, override with nil so that
-- the client doesn't think the document is newer and refuses to update
-- See: https://github.com/eclipse/eclipse.jdt.ls/issues/1695
local function fix_zero_version(workspace_edit)
  if workspace_edit and workspace_edit.documentChanges then
    for _, change in pairs(workspace_edit.documentChanges) do
      local text_document = change.textDocument
      if text_document and text_document.version and text_document.version == 0 then
        text_document.version = nil
      end
    end
  end
  return workspace_edit
end

local function on_textdocument_codeaction(err, actions, ctx)
  for _, action in ipairs(actions) do
    -- TODO: (steelsojka) Handle more than one edit?
    if action.command == 'java.apply.workspaceEdit' then -- 'action' is Command in java format
      action.edit = fix_zero_version(action.edit or action.arguments[1])
    elseif type(action.command) == 'table' and action.command.command == 'java.apply.workspaceEdit' then -- 'action' is CodeAction in java format
      action.edit = fix_zero_version(action.edit or action.command.arguments[1])
    end
  end

  handlers[ctx.method](err, actions, ctx)
end

local function on_textdocument_rename(err, workspace_edit, ctx)
  handlers[ctx.method](err, fix_zero_version(workspace_edit), ctx)
end

local function on_workspace_applyedit(err, workspace_edit, ctx)
  handlers[ctx.method](err, fix_zero_version(workspace_edit), ctx)
end

-- Non-standard notification that can be used to display progress
local function on_language_status(_, result)
  local command = vim.api.nvim_command
  command 'echohl ModeMsg'
  command(string.format('echo "%s"', result.message))
  command 'echohl None'
end

local root_files = {
  -- Single-module projects
  {
    'build.xml', -- Ant
    'pom.xml', -- Maven
    'settings.gradle', -- Gradle
    'settings.gradle.kts', -- Gradle
  },
  -- Multi-module projects
  { 'build.gradle', 'build.gradle.kts' },
}

return {
  default_config = {
    cmd = {
      'jdtls',
      '-configuration',
      get_jdtls_config_dir(),
      '-data',
      get_jdtls_workspace_dir(),
      get_jdtls_jvm_args(),
    },
    filetypes = { 'java' },
    root_dir = function(fname)
      for _, patterns in ipairs(root_files) do
        local root = util.root_pattern(unpack(patterns))(fname)
        if root then
          return root
        end
      end
    end,
    single_file_support = true,
    init_options = {
      workspace = get_jdtls_workspace_dir(),
      jvm_args = {},
      os_config = nil,
    },
    handlers = {
      -- Due to an invalid protocol implementation in the jdtls we have to conform these to be spec compliant.
      -- https://github.com/eclipse/eclipse.jdt.ls/issues/376
      ['textDocument/codeAction'] = on_textdocument_codeaction,
      ['textDocument/rename'] = on_textdocument_rename,
      ['workspace/applyEdit'] = on_workspace_applyedit,
      ['language/status'] = vim.schedule_wrap(on_language_status),
    },
  },
  docs = {
    description = [[
https://projects.eclipse.org/projects/eclipse.jdt.ls

Language server for Java.

IMPORTANT: If you want all the features jdtls has to offer, [nvim-jdtls](https://github.com/mfussenegger/nvim-jdtls)
is highly recommended. If all you need is diagnostics, completion, imports, gotos and formatting and some code actions
you can keep reading here.

For manual installation you can download precompiled binaries from the
[official downloads site](http://download.eclipse.org/jdtls/snapshots/?d)
and ensure that the `PATH` variable contains the `bin` directory of the extracted archive.

```lua
  -- init.lua
  require'lspconfig'.jdtls.setup{}
```

You can also pass extra custom jvm arguments with the JDTLS_JVM_ARGS environment variable as a space separated list of arguments,
that will be converted to multiple --jvm-arg=<param> args when passed to the jdtls script. This will allow for example tweaking
the jvm arguments or integration with external tools like lombok:

```sh
export JDTLS_JVM_ARGS="-javaagent:$HOME/.local/share/java/lombok.jar"
```

For automatic installation you can use the following unofficial installers/launchers under your own risk:
  - [jdtls-launcher](https://github.com/eruizc-dev/jdtls-launcher) (Includes lombok support by default)
    ```lua
      -- init.lua
      require'lspconfig'.jdtls.setup{ cmd = { 'jdtls' } }
    ```
    ]],
    default_config = {
      root_dir = [[{
        -- Single-module projects
        {
          'build.xml', -- Ant
          'pom.xml', -- Maven
          'settings.gradle', -- Gradle
          'settings.gradle.kts', -- Gradle
        },
        -- Multi-module projects
        { 'build.gradle', 'build.gradle.kts' },
      } or vim.fn.getcwd()]],
    },
  },
}