Emacs lsp-java Project Settings

Update: 2023-2-25 use eglot instead(in the last of the article)

Create a java project with third libriaries support

lsp-java is an awesome package for lsp-mode to open a java project. However, after some testing, I found it has difficulty in importing third party libraries with pure java project(not use maven, Gradle). Moreover, it only has a limited ability to interact with a Gradle project. However, it has great support for maven project, which means we can use maven to import third party java libraries. This article will focus on import a local library by maven.

Initialize a project

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mvn -B archetype:generate -DgroupId=PacMan -DartifactId=PacMan -Darchet
ypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4

This command will create a folder named PacMan=(=artifactId), where there is folder called src, and its structure is like:

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├── src
│   ├── main
│   │   └── java
│   │       └── PacMan(`groudId`)

If your groupId is "com.pacman.xx", then the directory structure may be like:

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├── src
│   ├── main
│   │   └── java
│   │       └── com
                └── pacman
                    └── xx

In our example, you can write code in the pacman folder.

Specify java version:

edit pom.xml file in the project root directory

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <!-- ... -->

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
  </properties>

  <!-- ... -->
</project>

Add third party libriary

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <!-- ... -->

  <dependencies>

    <!-- ... -->

    <dependency>
      <groupId>ucd.comp2011j</groupId>
      <artifactId>game-engine</artifactId>
      <version>1.00</version>
      <scope>system</scope>
      <systemPath>${basedir}/libs/COMP2011J.Game.Engine.jar</systemPath>
    </dependency>
  </dependencies>

  <!-- ... -->
</project>

Note that ${basedir} stands for the directory that pom.xml located.

Run Project:

create a Makefile in the project root directory:

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all: compile

compile:
	mvn package
	java -cp "target/PacMan-1.0-SNAPSHOT.jar:<your third party libriary relative path>" PacMan.GameStart # <Package Name>.<Class Name>

clean:
	mvn clean

Use command make to run, and make clean to clean

In doom emacs, you can type <SPC>pR and enter make to run the project

Eglot

make sure you have installed `jdtls`, and have a system java version >= 17

to run the java project, you can use this `Makefile`

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 # Makefile for c/c++ program
 #
 # ========================================
 # @author: Ziqi Yang<mr.ziqiyang@gmail.com>
 # @reference: https://makefiletutorial.com/#makefile-cookbook
 # ========================================

 SRC_DIR := src
 LIBS_DIR := libs
 BUILD_DIR := target
 ENTRY_POINT := Main
 ENTRY_FILE := $(SRC_DIR)/Main.java
 LIBS := $(shell find $(LIBS_DIR) -name "*.jar" | paste -sd ":" -)
 ARGS := 

.PHONY: build run
 build:
   mkdir -p $(BUILD_DIR)
   javac -d $(BUILD_DIR) -cp .:$(LIBS) -sourcepath $(SRC_DIR) $(ENTRY_FILE)

 run:
   java -cp $(BUILD_DIR):$(LIBS) $(ENTRY_FILE) $(ARGS)