jc.nvim

jc.nvim – successor of vim-javacomplete2 which use neovim's built-in LSP client and Eclipse JDT Language Server.

Read my blog post about it.

Main goal of this project is to migrate functionallty of jc2.

jc.nvim is a layer on top of an externally managed jdtls: it never starts the language server itself. Run jdtls with nvim-java, nvim-jdtls or nvim-lspconfig — jc.nvim hooks into whatever jdtls client attaches and adds:

• organize imports with smart selection regular classes;
• generate code (toString, hashCode, equals, constructors, accessors) with field selection;
• add abstract methods to implementing class;
• debug attach/launch via nvim-dap or vimspector, with per-project host/port memory;
• decompiled jdt:// class contents view;
• class creation methods from jc2.

Installation

Requirements:

• a running jdtls managed by nvim-java, nvim-jdtls or lspconfig. The

• for debug attach: the java-debug

• JCutilJol looks for the jol-cli jar in ~/.m2 and offers to download

Minimal setup using lazy.nvim (jdtls managed by nvim-java):

return {
  {
    "artur-shaik/jc.nvim",
    ft = { "java" },
    dependencies = {
      "nvim-java/nvim-java",
    },
    opts = {
      keys_prefix = "'j",
    },
  },
}

Configurations

All options go through setup(opts) (or the opts table of your plugin manager):

require("jc").setup({
  keys_prefix = "<leader>j",   -- prefix for the default mappings
  default_mappings = true,     -- install default mappings on attach
  autoformatonsave = false,  -- format java buffers on save
  debug_backend = nil,         -- "dap" | "vimspector" | nil (auto-detect)
  basedir = nil,               -- data dir, default ~/.local/share/jc.nvim
  updateconfigonnewfile = true, -- refresh jdtls build path on new java files
  on_attach = nil,             -- function(client, bufnr) extra hook
})

The legacy g:jcdefaultmappings, g:jcautoformaton_save, g:jcdebugbackend and g:jc_basedir variables still work as a fallback when the corresponding option is not passed to setup.

A java file created in-editor isn't on jdtls' build path until the project configuration is refreshed, so go-to-definition returns nothing on it (while find-references still works off the search index). With updateconfigonnewfile (default true), jc.nvim detects such files and fires :JCutilUpdateConfig for them on first write automatically. Set it to false to refresh manually.

What it adds over plain nvim-jdtls

| Feature | nvim-jdtls | jc.nvim | |---|---|---| | Code generation (toString/equals/hashCode/constructors/accessors) | via code actions | dedicated commands and mappings with field selection | | Organize imports | code action | smart mode remembering preferred classes per project | | Debug attach | manual dap config | JCdebugAttach with per-project host/port memory, dap or vimspector | | Class creation from templates | — | JCgenerateClass prompt DSL | | Extract refactorings | yes | built-in (java/inferSelection + java/getRefactorEdit) | | Classpath-aware javap/jshell/jol | yes | built-in |

:checkhealth jc verifies the setup; :help jc for full docs.

Commands

• JCdebugAttach – attach debugger (nvim-dap or vimspector, see debug_backend);
• JCdebugLaunch – launch debug session;
• JCdapAttach / JCvimspectorAttach – attach using a specific backend;
• JCdebugWithConfig – start debug session using predefined vimspector's configuration;
• JCimportsOrganizeSmart – automatically organize imports using regular classes list;
• JCimportsOrganize – automatically organize imports choosing from available classes list;
• JCgenerateToString – choose fields and method to generate toString;
• JCgenerateHashCodeAndEquals – choose fields to generate hashCode and equals;
• JCgenerateAccessors – choose fields for accessors generation;
• JCgenerateAccessorGetter – generate getter for a field;
• JCgenerateAccessorSetter – generate setter for a field;
• JCgenerateAccessorSetterGetter – generate getter and setter for a field;
• JCgenerateConstructorDefault – generate constructor with no arguments;
• JCgenerateConstructor – choose fields for constructor;
• JCgenerateAbstractMethods – generate abstract methods;
• JCgenerateClass – start class generation user input prompt;
• JCtoggleAutoformat – enable/disable autoformat file on save;
• JCutilUpdateConfig – re-read project configuration (pom/gradle);
• JCutilWipeWorkspace – delete the jdtls workspace (eclipse index) and restart the server;
• JCrefactorExtractVar – extract variable;
• JCrefactorExtractMethod – extract method (visual range);
• JCutilJshell – execute java shell with project classpath;
• JCutilBytecode – extract bytecode for class (javap);
• JCutilJol – analyze object layout scheme using jol.jar.

Default mappings

Installed on jdtls attach when default_mappings is enabled. <p> is keys_prefix (default <leader>j).

| Mode | Keys | Action | |---|---|---| | n | <p>i | organize imports (smart) | | n | <p>I | organize imports (manual selection) | | i | <C-j>i | organize imports | | n | <p>ts | generate toString() | | n | <p>eq | generate hashCode() and equals() | | n | <p>A | generate accessors (field selection) | | n | <p>s / <p>g | generate setter / getter | | n | <leader>ja | generate getter and setter | | i | <C-j>s / <C-j>g / <C-j>a | accessor generation | | n | <p>c | generate constructor (field selection) | | n | <p>cc | generate default constructor | | n | <p>m, i <C-j>m | generate abstract methods | | n | <p>n | new class prompt | | n | <p>da / <p>dl | debug attach / launch | | v | <p>re / <p>rm | extract variable / method (selection) | | n | <p>re | extract variable (inferred at cursor) |

Class creation

Prompt scheme, for class creation:

template:[subdirectory]:/package.ClassName extends SuperClass implements Interface(String str, public Integer i):contructor:toString:equals

A: (optional) template - which will be used to create class boilerplate. Some existed templates: junit, interface, exception, servlet, etc;

B: (optional) subdirectory in which class will be put. For example: test, androidTest;

C: class name and package. With / will use backsearch for parent package to put in it. Without / put in relative package to current;

D: (optional) extends and implements classes will be automatically imported;

E: (optional) private str variable, and public i variable will be added to class;

F: (optional) contructor using all fields and toString will be created. Also hashCode and equals can be used.