Emacs Java IDE using 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
• Project explorer integration - treemacs
• Integration with Spring Initializr

Screenshot

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)

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. 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 projectile :ensure t)
(use-package treemacs :ensure t)
(use-package yasnippet :ensure t)
(use-package lsp-mode :ensure t)
(use-package hydra :ensure t)
(use-package company-lsp :ensure t)
(use-package lsp-ui :ensure t)
(use-package lsp-java :ensure t :after lsp
  :config (add-hook 'java-mode-hook 'lsp))

(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-treemacs :after (treemacs))

Supported commands

LSP Mode commands

• 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-restart-workspace - 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

• 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:

• 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

Treemacs

lsp-java provides experimental integration with treemacs which provides option to navigate through package dependecies, namespaces, classes and resources.

• lsp-java-treemacs-register activates lsp-java/treemacs integration.
• lsp-java-treemacs-unregister deactivates lsp-java/treemacs integration.
• lsp-java-update-project-uris refresh the project URIs.

Classpath browsing

lsp-java the command lsp-java-classpath-browse which allows users to browse the structure of current projects classpath. From that view the users could go to the particular item.

Spring Initializr

lsp-java provides a frontend for Spring Initializr which simplifies the creation of Spring Boot projects directly from Emacs via lsp-java-spring-initializr.

Supported settings

• 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-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.

Additional packages

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

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.