Java support for lsp-mode using the Eclipse JDT Language Server.

Features

LSP java mode supports the following JDT Features:

• As you type reporting of parsing and compilation errors (via flycheck/lsp-ui)
• Code completion - using company-lsp or builtin complete-at-point
• Javadoc hovers - using lsp-ui
• Code actions - using lsp-ui
• Code outline - using builtin imenu
• Code navigation - using builtin xref
• Code lens (references/implementations) - using builtin xref
• Highlights
• Code formatting
• Maven pom.xml project support
• Limited Gradle support
• Visual debugger - dap-mode
• Test runner - dap-mode

Installation

Spacemacs

lsp-java is included in spacemacs (for now only on the dev branch). If you are using the development version of spacemacs you can simply add (java :variables java-backend 'lsp) to dotspacemacs-configuration-layers.

Install via melpa

The recommended way to install LSP Java is via package.el - the built-in package manager in Emacs. LSP Java is available on the two major package.el community maintained repos - MELPA Stable and MELPA.

M-x package-install [RET] lsp-java [RET]

Then add the following lines to your .emacs and open a file from the any of the specified projects.

(require 'lsp-java)
(add-hook 'java-mode-hook #'lsp-java-enable)

Eclipse JDT Language Server

lsp-java will automatically detect when the server is missing and it will download Eclipse JDT Language Server before the first startup. The server installation will be in lsp-java-server-install-dir. It will detect whether dap-mode is present and it will download the required server side plugins/components. If you want to update the server you can run lsp-java-update-server. To run specific version of Eclipse JDT Language Server use lsp-java-server-install-dir.

Quick start

Minimal configuration with company-lsp and lsp-ui and dap-mode. Make sure you have replaced the XXX placeholder with the list of the projects you want to import. Now you can explore the methods under lsp-java-*, dap-java-*, dap-*, and lsp-*

(require 'cc-mode)

(condition-case nil
    (require 'use-package)
  (file-error
   (require 'package)
   (add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/"))
   (package-initialize)
   (package-refresh-contents)
   (package-install 'use-package)
   (require 'use-package)))

(use-package lsp-mode
  :ensure t
  :init (setq lsp-eldoc-render-all nil
              lsp-highlight-symbol-at-point nil))

(use-package company-lsp
  :after  company
  :ensure t
  :config
  (add-hook 'java-mode-hook (lambda () (push 'company-lsp company-backends)))
  (setq company-lsp-cache-candidates t)
  (push 'java-mode company-global-modes))

(use-package lsp-ui
  :ensure t
  :config
  (setq lsp-ui-sideline-update-mode 'point))

(use-package dap-mode
  :ensure t
  :after lsp-mode
  :config
  (dap-mode t)
  (dap-ui-mode t))

(use-package dap-java
  :after 'lsp-java)

(use-package lsp-java
  :ensure t
  :requires (lsp-ui-flycheck lsp-ui-sideline)
  :config
  (add-hook 'java-mode-hook  'lsp-java-enable)
  (add-hook 'java-mode-hook  'flycheck-mode)
  (add-hook 'java-mode-hook  'company-mode)
  (add-hook 'java-mode-hook  (lambda () (lsp-ui-flycheck-enable t)))
  (add-hook 'java-mode-hook  'lsp-ui-mode))

Supported commands

LSP Mode commands

Command name	Description
lsp-execute-code-action	Execute code action.
lsp-rename	Rename symbol at point
lsp-describe-thing-at-point	Display help for the thing at point.
lsp-goto-type-definition	Go to type definition
lsp-goto-implementation	Go to implementation
lsp-workspace-restart	Restart project
lsp-format-buffer	Format current buffer
lsp-symbol-highlight	Highlight all relevant references to the symbol under point.
lsp-workspace-folders-add	Add workspace folder
lsp-workspace-folders-remove	Remove workspace folder
lsp-workspace-folders-switch	Switch workspace folder

LSP Java commands

Command name	Description
lsp-java-organize-imports	Organize imports
lsp-java-build-project	Perform partial or full build for the projects
lsp-java-update-project-configuration	Update project configuration
lsp-java-actionable-notifications	Resolve actionable notifications
lsp-java-update-user-settings	Update user settings (Check the options in the table bellow.)
lsp-java-update-server	Update server instalation.

Refactoring

LSP Java provides rich set of refactorings via Eclipse JDT Language Server code actions and some of them are bound to Emacs commands:

Command name	Description
lsp-java-extract-to-constant	Extract constant refactoring
lsp-java-add-unimplemented-methods	Extract constant refactoring
lsp-java-create-parameter	Create parameter refactoring
lsp-java-create-field	Create field refactoring
lsp-java-create-local	Create local refactoring
lsp-java-extract-method	Extract method refactoring
lsp-java-add-import	Add missing import

Supported settings

Setting	Description
lsp-java-server-install-dir	Install directory for eclipsejdtls-server
lsp-java-java-path	Path of the java executable
lsp-java-workspace-dir	LSP java workspace directory
lsp-java-workspace-cache-dir	LSP java workspace cache directory
lsp-java-vmargs	Specifies extra VM arguments used to launch the Java Language Server
lsp-java-incomplete-classpath	Specifies the severity of the message when the classpath is incomplete for a Java file
lsp-java-update-build-configuration	Specifies how modifications on build files update the Java classpath/configuration
lsp-java-import-exclusions	Configure glob patterns for excluding folders
lsp-java-favorite-static-members	Defines a list of static members or types with static members
lsp-java-import-order	Defines the sorting order of import statements
lsp-java-trace-server	Traces the communication between Emacs and the Java language server
lsp-java-enable-file-watch	Defines whether the client will monitor the files for changes
lsp-java-format-enabled	Specifies whether or not formatting is enabled on the language server
lsp-java-format-settings-url	Specifies the file path to the formatter xml url
lsp-java-format-settings-profile	Specifies the formatter profile name
lsp-java-format-comments-enabled	Preference key used to include the comments during the formatting
lsp-java-save-action-organize-imports	Organize imports on save
lsp-java-organize-imports	Specifies whether or not organize imports is enabled as a save action
lsp-java-bundles	List of bundles that will be loaded in the JDT server
lsp-java-import-gradle-enabled	Enable/disable the Gradle importer
lsp-java-import-maven-enabled	Enable/disable the Maven importer
lsp-java-auto-build	Enable/disable the 'auto build'
lsp-java-progress-report	[Experimental] Enable/disable progress reports from background processes on the server
lsp-java-completion-guess-arguments	When set to true, method arguments are guessed when a method is selected from as list of code assist proposals.

Screenshot

Additional packages

• lsp-ui : Flycheck, documentation and code actions support.
• company-lsp : LSP company backend.

FAQ

• LSP Java is showing to many debug messages, how to stop that?

Add the following configuration.

(setq lsp-inhibit-message t)

• lsp-ui does not display all of the actions on the current point(e. g "Extract constant")?

LSP UI by default sends current line bounds for action region which breaks forces JDT server to return only "Extract method action."

(setq lsp-ui-sideline-update-mode 'point)

• LSP Java does not provide completion, go to definition for some of the files?

When particular file is not part of imported project Eclipse JDT Language Server could not calculate the current classpath.