Nightly build of Neovim with JDTLS (java language server) not recognizing JAR files in ${CLASSPATH}

Question

I have added the junit jar file in my ${CLASSPATH} environment variable, but when I use the lsp for neovim it doesn't recognize the functions and imports from the JAR file.

import static org.junit.Assert.assertEquals;     ■ The import org.junit cannot be resolved
  1 import static org.junit.Assert.assertTrue;     ■ The import org.junit cannot be resolved
  2 import static org.junit.Assert.fail;     ■ The import org.junit cannot be resolved
  3
  4 import java.util.Comparator;
  5 import java.util.Arrays;
  6 import java.util.List;
  7 import java.util.ArrayList;
  8
  9 import org.junit.Test;     ■ The import org.junit cannot be resolved
 10 import org.junit.Before;     ■ The import org.junit cannot be resolved

Does anyone know a way to add the ${CLASSPATH} to the imports and "stuff" that jdtls recognizes?

Seabass · Answer 1 · 2021-05-03T00:22:23.227

One has to specify the correct plugin to initialize the (Eclipse)language server within the JDK. We can do this by creating a shell script that is called by your nvim LSP plugin/config.

First you have to locate the equinox_launcher jar file, which is located in the eclipse/jdt-language-server/plugin folder and add it to your script.

Linux shell script should look something like this:

#!/usr/bin/env/ bash
    
JAR="path/to/your/eclipse/build/plugins/org.eclipse.equinox.launcher_longnumberhere.jar" 
GRADLE_HOME=$HOME/where_gradle_lives/gradle $JAVA_HOME/or_absolute_path \/bin/java \
              -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=1044 \
              -Declipse.application=org.eclipse.jdt.ls.core.id1 \
              -Dosgi.bundles.defaultStartLevel=4 \
              -Declipse.product=org.eclipse.jdt.ls.core.product \
              -Dlog.level=ALL -noverify \
              -Xmx1G -jar echo $(JAR) \ // points to the plugin
              -configuration ./config_linux \ // points to the config folder within jdtls  
              -data /path/to/data \
              --add-modules=ALL-SYSTEM \
              --add-opens java.base/java.util=ALL-UNNAMED \
              --add-opens java.base/java.lang=ALL-UNNAMED

Win batch script should look something like this:

SET "JAR=path\to\your\eclipse\build\plugins\org.eclipse.equinox.launcher_longnumberhere.jar"
SET "GRADLE_HOME=path\where\gradle\lives\gradle %JAVA_HOME%\or_absolute_path\bin\java"^
      -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=1044^
      -Declipse.application=org.eclipse.jdt.ls.core.id1^
      -Dosgi.bundles.defaultStartLevel=4^
      -Declipse.product=org.eclipse.jdt.ls.core.product^
      -Dlog.level=ALL^ 
      -noverify^
      -Xmx1G -jar echo %JAR%^ // this points to the plugin
      -configuration .\config_win^ // points to the config folder within jdtls  
      -data \path\to\data^ 
      --add-modules=ALL-SYSTEM^
      --add-opens java.base/java.util=ALL-UNNAMED^
      --add-opens java.base/java.lang=ALL-UNNAMED

After the agentlib line, you can add the modules you need. For further conveniences, the java_lsp.sh or java_lsp.bat can be included in a environment path.
The jdtls target directories can vary if you build from source, or (recommended) use a Milestone build.
https://download.eclipse.org/jdtls/milestones/

For more detailed information you can check out:

Neovim built in LSP documentation:

https://neovim.io/doc/user/lsp.html

Guide + documentation regarding JDTLS:

https://github.com/eclipse/eclipse.jdt.ls

Guide + Examples Regarding JDTLS client plugin for nvim written in lua:

This doesn't seem to answer the question. This step has already been done, what they are asking is how to make jdtls recognize dependencies. — Emiliano Ruiz, Feb 24 '22 at 21:10
"Does anyone know a way to add the ${CLASSPATH} to the imports and "stuff" that jdtls recognizes?" My answer clearly describes this. — Seabass, Feb 26 '22 at 08:18

score 0 · Answer 2 · edited Feb 26 '22 at 18:10

I recently went through the process of trying to get this to work (note that I used jdtls-launcher to run JDTLS, not sure if that affects whether my answer will work), and essentially found that you need to add a line to the .classpath file in the workspace directory that JDTLS automatically creates when you start a new project (located at ~/.cache/jdtls-workspace/my_project_name_with_numbers_after for me). According to section 3.4 of this documentation, the line should look like this:

<classpathentry kind="lib" path="/path/to/junit-platform-console-standalone-1.8.2.jar"/>

Where /path/to/junit-platform-console-standalone-1.8.2.jar is wherever you may have downloaded junit-platform-console-standalone-1.8.2.jar from here (or whatever version of JUnit you want).

However, I explain what I did to get it to work in more detail in this GitHub issue, so I'd suggest you check that out for more information.

Nightly build of Neovim with JDTLS (java language server) not recognizing JAR files in ${CLASSPATH}

2 Answers2