Meghanada-Mode

A Better Java Development Environment for Emacs

Meghanada is a new minor-mode (meghanada-mode) that aims at improving the editing experience for Java. It works by using a combination of an Emacs package and meghanada-server.

Features:

• Easy install
• Auto-update server module
• Gradle and Maven and Eclipse project support
• No need build tool's plugin
• Run build tool task
• Compile your project
• Syntax check and analyze java source (flycheck-meghanada)
• Support Generic Types and Lambda
• Code completion with company-mode (company-meghanada)
• Optimize import and sort
• Find definitions and references using builtin xref
• Run JUnit test (include test runner)
• Diagnostic reporting with flycheck (flycheck-meghanada)
• Show symbol's type info with el-doc
• Full-featured text search

Meghanada is tested under Linux, Windows and macOS.

(Welcome contributions !)

Dependencies

Meghanada has been developed Emacs 25.1.1

Elisp dependencies

Language Server

meghanada-mode require meghanada-server and JDK (not JRE).

meghanada-server is The language server. The language server provides a simple interface between meghanada-mode and It is a protocol based on a simple S-expression. This server is developed in Java and supports Java version 8 or later.

The architecture between the server and the client is very similar to the language server protocol. The server retrieves and updates all information in the Java project at file save time and at compile time. If the autocompletion information is not displayed correctly, please try to fix the compilation error first.

Installation

Elisp

Install meghanada from melpa.

Configuration

An example is shown below.

(require 'meghanada)
(add-hook 'java-mode-hook
          (lambda ()
            ;; meghanada-mode on
            (meghanada-mode t)
            (flycheck-mode +1)
            (setq c-basic-offset 2)
            ;; use code format
            (add-hook 'before-save-hook 'meghanada-code-beautify-before-save)))
(cond
   ((eq system-type 'windows-nt)
    (setq meghanada-java-path (expand-file-name "bin/java.exe" (getenv "JAVA_HOME")))
    (setq meghanada-maven-path "mvn.cmd"))
   (t
    (setq meghanada-java-path "java")
    (setq meghanada-maven-path "mvn")))

Meghanada-Server

The server will be automatically installed to ~/.emacs.d/meghanada/meghanada-x.x.jar.

If you open a java file and set meghanada-mode, a meghanada-server process starts automatically and connects to your Emacs.

Updating

The server will be automatically updated. To manually update bellows, type

M-x meghanada-update-server

Manual Server Installation

The server will be installed and updated automatically.

If you set it up manually, please follow the instructions below.

Download meghanada-setup.jar

A meghanada-setup.jar is a small program that automatically updates the server.

This can be downloaded from:

https://github.com/mopemope/meghanada-server/releases/download/v1.0.13/meghanada-setup-0.0.2.jar

Move the downloaded setup.jar to .emacs.d/meghanada/. Start Emacs and enable meghanada-mode.

Autocompletion

Autocompletion is supported by company-mode. Supported autocompletions are as follows

• Import Class
• Class
• Method
• Field
• Local Variable

If the completion candidates are not displayed correctly, try to fix the compilation error first. Auto-completion matching is optional. Try typing the following to find out more.

M-x customize-group RET meghanada and M-x customize-group RET company-meghanada.

Syntax/error checking

Syntax checks, such as compile errors, are supported by flycheck. This includes -Xlint warnings.

Code formatter

meghanada-mode uses google-java-format by default for formatter.

It also support Eclipse formatter.

If you want to customize and use the Eclipse formatter please export the formatter settings from Eclipse to a file.

Then rename the file to meghanadaFormatter.xml and place it in the project root or subproject root. Meghanada will automatically load and import it.

If you want to use a system wide formatter, deploy the file to $HOME/.emacs.d/meghanada/meghanadaFormatter.xml.

Debug

meghanada-mode has no debugger yet. However, the external debugger is supported.

if you want to debug your code, execute meghanada-debug-xxxx function and then use realgud, etc.

# in Emacs now:
 M-x meghanada-debug-junit-class
 Please wait ...
 M-x realgud:jdb
 Run jdb (like this): jdb -attach 6006
 Set uncaught java.lang.Throwable
   Set deferred uncaught java.lang.Throwable
   Initializing jdb ...
   >
   VM Started: No frames on the current call stack

   main[1] stop at example.MyClass:100 // set breakpoint
   main[1] run

Customize

To customize other aspects of its behavior, type M-x customize-group RET meghanada and M-x customize-group RET company-meghanada.

Troubleshooting

See *meghanada-server-log* buffer. or (temporary-file-directory)meghanada_server_(user-uid).log, e.g. /tmp/meghanada_server_1000.log.

Please press C-g when emacs seems to hang.

Usage

Here is a list of available interactive commands.

Definitions and references can be found from the xref command.

meghanada-install-server

Download and install meghanada-server jar.

meghanada-update-server

Download and update meghanada-server jar. and restart the server process.

meghanada-server-start

Start meghanada-server process and connect to the server.

meghanada-mode call this function by default. when open java file and set meghanada-mode.

meghanada-restart

Restart meghanada-server process and client process.

meghanada-server-kill

Kill meghanada-server process.

meghanada-client-direct-connect

Connect to other meghanada-server directly.

meghanada-client-connect

Connect to meghanada-server . Call automatically at the start meghanada-mode.

meghanada-client-disconnect

Disconnect from meghanada-server .

meghanada-client-ping

Send ping meghanada-server

meghanada-clear-cache

Clear meghanada-server's project cache data.

meghanada-import-all (C-c C-r i)

Add import all unqualified classes.

meghanada-optimize-import (C-c C-r o)

Import all and remove unused import statement.

The format of the import statement will be in google-java-format.

meghanada-import-at-point

Add import statement from symbol at point.

meghanada-local-variable (C-c C-r r)

Introduce local variable. (need expression is end ;)

meghanada-compile-file (C-c C-c C-c)

Compile file (and related files).

meghanada-project-show

Show project details.

meghanada-project-compile (C-c C-c c)

Compile project (full build and reindex).

meghanada-switch-testcase (C-M-,)

Switch test case or source.

meghanada-exec-main

Run main class.

meghanada-debug-main

Debug main class.

meghanada-search-everywhere

It does a full-text search based search (class, method, symbol (field)).

meghanada-search-everywhere-ex

It does a full-text search expert-mode (Enter a query for Lucene).

Here is a list of fields that can be used in the search.

• package
• class
• method
• symbol
• usage
• dc (method's or field's declaring class)

ex. Seach class name contains Search.

class:*Search*

It can also use AND operator.

dc:*Optional* AND usage:get

meghanada-typeinfo

Show type hierarchies and implements interfaces.

meghanada-run-junit-class (C-c C-c C-t)

Run JUnit test class.

meghanada-run-junit-test-case (C-c C-c t)

Run JUnit test case (select from imenu).

meghanada-debug-junit-class (C-c C-c C-t)

Debug JUnit test class.

meghanada-debug-junit-test-case (C-c C-c t)

Debug JUnit test case (select from imenu).

meghanada-run-task (C-c C-v t)

Run build tool task.

meghanada-code-beautify

Format buffer code. The default formatter is google-java-format

TODO

• Refactoring

Contributing

Contributions are extremely welcome! Please push PR to dev branch.

License

GPL v3, See LICENSE file.