nvim-jdtls

Extensions for the built-in Language Server Protocol support in Neovim (>= 0.5) for eclipse.jdt.ls.

Warning: This is early state. Neovim 0.5 hasn't been released yet, so APIs can change and things may break.

Extensions

• organize_imports command to organize imports
• extract_variable command to introduce a local variable
• extract_method command to extract a block of code into a method
• Open class file contents
• Code action extensions
  • Generate constructors
  • Generate toString function
  • hashCode and equals generation.
  • Extract variables or methods
  • Generate delegate methods
• javap command to show bytecode of current file
• jol command to show memory usage of current file (jol_path must be set)
• jshell command to open up jshell with classpath from project set
• Integration with nvim-dap

Take a look at a demo to see some of the functionality in action.

Plugin Installation

• Requires Neovim HEAD/nightly
• nvim-jdtls is a plugin. Install it like any other Vim plugin.
• Call :packadd nvim-jdtls if you install nvim-jdtls to 'packpath'.

LSP Installation

For nvim-jdtls to work, eclipse.jdt.ls needs to be installed.

To build eclipse.jdt.ls from source, switch to a folder of your choice and run:

git clone https://github.com/eclipse/eclipse.jdt.ls.git
cd eclipse.jdt.ls
./mvnw clean verify

Create a launch script with the following contents. But don't forget to adapt the paths.

• $HOME/dev/eclipse needs to be changed to the folder where you cloned the repository.
• $HOME/workspace needs to be changed to where you want eclipse.jdt.ls to save settings for workspaces.
• /usr/lib/jvm/java-14-openjdk/bin/java needs to be changed to point to your Java installation.

If you're using Java < 9, remove the add-modules and -add-opens options.

#!/usr/bin/env bash

JAR="$HOME/dev/eclipse/eclipse.jdt.ls/org.eclipse.jdt.ls.product/target/repository/plugins/org.eclipse.equinox.launcher_*.jar"
GRADLE_HOME=$HOME/gradle /usr/lib/jvm/java-14-openjdk/bin/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 \
  -Xms1g \
  -Xmx2G \
  -jar $(echo "$JAR") \
  -configuration "$HOME/dev/eclipse/eclipse.jdt.ls/org.eclipse.jdt.ls.product/target/repository/config_linux" \
  -data "$HOME/workspace" \
  --add-modules=ALL-SYSTEM \
  --add-opens java.base/java.util=ALL-UNNAMED \
  --add-opens java.base/java.lang=ALL-UNNAMED

The script must be placed in a folder that is part of $PATH. To verify that the installation worked, launch it in a shell. You should get the following output:

Content-Length: 126

{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"Sep 16, 2020, 8:10:53 PM Main thread is waiting"}}

Configuration

To use nvim-jdtls, you need to setup a LSP client. In your init.vim add the following:

if has('nvim-0.5')
  packadd nvim-jdtls
  lua jdtls = require('jdtls')
  augroup lsp
    au!
    au FileType java lua jdtls.start_or_attach({cmd={'java-lsp.sh'}})
  augroup end
endif

java-lsp.sh needs to be changed to the name of the shell script created earlier.

The argument passed to start_or_attach is the same config mentioned in :help vim.lsp.start_client. You may want to configure some settings via the init_options. See the eclipse.jdt.ls Wiki for an overview of available options.

Usage

nvim-jdtls extends the capabilities of the built-in LSP support in Neovim, so all the functions mentioned in :help lsp will work.

nvim-jdtls provides some extras, for those you'll want to create additional mappings:

-- `code_action` is a superset of vim.lsp.buf.code_action and you'll be able to
-- use this mapping also with other language servers
nnoremap <A-CR> <Cmd>lua require('jdtls').code_action()<CR>
vnoremap <A-CR> <Esc><Cmd>lua require('jdtls').code_action(true)<CR>
nnoremap <leader>r <Cmd>lua require('jdtls').code_action(false, 'refactor')<CR>

nnoremap <A-o> <Cmd>lua require'jdtls'.organize_imports()<CR>
nnoremap crv <Cmd>lua require('jdtls').extract_variable()<CR>
vnoremap crv <Esc><Cmd>lua require('jdtls').extract_variable(true)<CR>
vnoremap crm <Esc><Cmd>lua require('jdtls').extract_method(true)<CR>


-- If using nvim-dap
nnoremap <leader>df <Cmd>lua require'jdtls'.test_class()<CR>
nnoremap <leader>dn <Cmd>lua require'jdtls'.test_nearest_method()<CR>

Some methods are better exposed via commands. As a shortcut you can also call :lua require('jdtls.setup').add_commands() to declare these. It's recommended to call add_commands within the on_attach callback that can be set on the config table which is passed to start_or_attach.

command! -buffer JdtCompile lua require('jdtls').compile()
command! -buffer JdtUpdateConfig lua require('jdtls').update_project_config()
command! -buffer JdtJol lua require('jdtls').jol()
command! -buffer JdtBytecode lua require('jdtls').javap()
command! -buffer JdtJshell lua require('jdtls').jshell()

nvim-dap

nvim-jdtls provides integration with nvim-dap.

For this to work, eclipse.jdt.ls needs to load the java-debug extension. To do so, clone java-debug and run ./mvnw clean install in the cloned directory, then extend the initializationOptions with which you start eclipse.jdt.ls:

config['init_options'] = {
  bundles = {
    vim.fn.glob("path/to/java-debug/com.microsoft.java.debug.plugin/target/com.microsoft.java.debug.plugin-*.jar")
  };
}

You also need to call require('jdtls').setup_dap() to have it register a java adapter for nvim-dap and to create configurations for all discovered main classes:

config['on_attach'] = function(client, bufnr)
  require('jdtls').setup_dap()
end

Furthermore, nvim-jdtls supports running and debugging tests. For this to work the bundles from vscode-java-test need to be installed:

• Clone the repo
• Run npm install
• Run npm run build-plugin
• Extend the bundles:

local bundles = {
  vim.fn.glob("path/to/java-debug/com.microsoft.java.debug.plugin/target/com.microsoft.java.debug.plugin-*.jar"),
};
vim.list_extend(bundles, vim.split(vim.fn.glob("/path/to/microsoft/vscode-java-test/server/*.jar"), "\n"))
config['init_options'] = {
  bundles = bundles;
}