Error when trying to launch java debug session

  Hi guys, i am trying to launch the debugger for java in theia. I configure the debugger accordingly:
  "version": "0.2.0",
  "configurations": [
          "type": "java",
          "name": "Debug (Launch)",
          "request": "launch",
          "cwd": "${workspaceFolder}",
          "console": "internalConsole",
          "stopOnEntry": false,
          "mainClass": "test.Test",
          "args": ""

However when i try to launch the debug session, i get the following error:

 root ERROR Request executeCommand failed with error: The command '' cannot be executed. There are no active handlers available for the command. (args: ["file:///home","test.Test",null,false,{"_isCancelled":false}])

I double checked that java/debug package is installed, so i suspect i am missing some sort of config or package. Hope you guys can point me the right direction.

P.S. the package.json is:

    "private": true,
    "dependencies": {
        "@theia/core": "next",
        "@theia/python": "next",
        "@theia/java": "next",
        "@theia/java-debug": "next",
        "@theia/debug": "next",
        "@theia/messages": "next",
        "@theia/navigator": "next",
        "@theia/terminal": "next",
        "@theia/outline-view": "next",
        "@theia/preferences": "next",
        "@theia/monaco": "next",
        "@theia/getting-started": "next",
        "@theia/git": "next",
        "@theia/file-search": "next",
        "@theia/markers": "next",
        "@theia/textmate-grammars": "next",
        "@theia/search-in-workspace": "next",
        "@theia/json": "next",
        "@theia/editor-preview": "next",
        "@theia/extension-manager": "next",
        "@theia/plugin-ext": "next"
    "devDependencies": {
        "@theia/cli": "next"

[original thread by Simas Joneliunas]

Are you sure that Java LS is running for your project? It should contribute such commands.

[Simas Joneliunas]

thanks. That was it. My docker container was at fault!

[Alvin Richards]

@simas-joneliunas what did you change in your dockerfile to make this work? I’m stuck!

@alvin-richards Are you using our “theia-java” image (src here:, also available on dockerhub)? If so it’s not been updated yet to support Theia plugins or debug. One could take inspiration in the Theia browser example, to find Theia extensions that need to be added (