Electron/Java compatiblity?

[vrmerlin]

I'm trying to create an Electron application that uses Java to access some legacy code. I could get it to work with NW.js, but I can't seem to get it to work with Electron on Windows. Here's what I've done:

• Installed the windows-build-tools npmjs module (that in turns installs Python and the MS VS command line build).

• Cloned the electron-quick-start and verified that it built and ran correctly on my system. Installed the Java module (version 0.80) into package.json. After downloading, it did a successful build process.

• Removed the node_modules directory and did an npm install again. Again, I can see the Java support files (.cpp) compiling as expected, with no errors.

• Ran the electron-quick-start again, and it came up with no problems.

• Added the line const java = require('java') to the main.js of electron-quick-start

• When I run the sample, I see the following error:

App threw an error during load
Error: A dynamic link library (DLL) initialization routine failed.
\\?\C:\devel\electron-quick-start\node_modules\java\build\Release\nodejavabridge_bindings.node
at process.module.(anonymous function) [as dlopen] (ELECTRON_ASAR.js:173:20)
at Object.Module._extensions..node (module.js:598:18)
at Object.module.(anonymous function) [as .node] (ELECTRON_ASAR.js:173:20)
at Module.load (module.js:488:32)
at tryModuleLoad (module.js:447:12)
at Function.Module._load (module.js:439:3)
at Module.require (module.js:498:17)
at require (internal/module.js:20:19)
at C:\devel\electron-quick-start\node_modules\java\lib\nodeJavaBridge.js:21:16
at Object.<anonymous> (C:\devel\electron-quick-start\node_modules\java\lib\nodeJavaBridge.js:316:2)

• At this point, I tried installing and running electron-rebuild. When I re-ran the sample, I then got this error:

Error: Cannot find module '../build/jvm_dll_path.json'
at Module._resolveFilename (module.js:470:15)
at Function.Module._resolveFilename (C:\devel\electron-quick-start\node_modules\electron\dist\resources\electron.asar\common\reset-search-paths.js:35:12)
at Function.Module._load (module.js:418:25)
at Module.require (module.js:498:17)
at require (internal/module.js:20:19)
at C:\devel\electron-quick-start\node_modules\java\lib\nodeJavaBridge.js:3:21
at Object.<anonymous> (C:\devel\electron-quick-start\node_modules\java\lib\nodeJavaBridge.js:316:2)
at Module._compile (module.js:571:32)
at Object.Module._extensions..js (module.js:580:10)
at Module.load (module.js:488:32)

• So, I thought maybe at this point, I need to rebuild the Java, so I did the following:

node-gyp rebuild
npm run postinstall
cd ..\..

Unfortunately, when I ran the sample, I simply got the first error message again. Any ideas out there? I feel like I'm really close, but can't quite get the build steps correct. John

[dasarindam]

Me too trying the same. Tried all the thing ... I didnt get the error of missing JVM file. how did you tried to rebuilt the electron ? What command did you used ?

[dasarindam]

I build java. I build electron too. Now it goes back to 1st erreor. ELECTRON_ASAR.js:173:20 ....

[vrmerlin]

Here are the two steps I did to rebuild Electron:

npm install --save-dev electron-rebuild
.\node_modules\.bin\electron-rebuild.cmd

[vrmerlin]

Also, I tried running the command npm rebuild --runtime=electron --target=1.6.0 --msvs_version=2015 --arch=x64 and got this compile error in the Java code:

..\src\utils.cpp(494): error C3083: 'NewStringType': the symbol to the left of a '::' must be a type [C:\devel\narac-sample-ui\node_modules\java\build\nodejavabridge
_bindings.vcxproj]
..\src\utils.cpp(494): error C2039: 'kNormal': is not a member of 'v8' [C:\devel\narac-sample-ui\node_modules\java\build\nodejavabridge_bindings.vcxproj]
  C:\Users\fisher23\.node-gyp\iojs-1.6.0\deps\v8\include\v8.h(65): note: see declaration of 'v8'
..\src\utils.cpp(494): error C2065: 'kNormal': undeclared identifier [C:\devel\narac-sample-ui\node_modules\java\build\nodejavabridge_bindings.vcxproj]
..\src\utils.cpp(494): error C2228: left of '.ToLocalChecked' must have class/struct/union [C:\devel\narac-sample-ui\node_modules\java\build\nodejavabridge_bindings.
vcxproj]

I should comment that I can't get this to work on Linux now, either. At one point it worked, but I think it was the luck of versioning (Node/Electron/Java/whatever) that it just happened to work. I'm getting the same error behaviors on that OS.

[dasarindam]

Still i could not make it work... Can you let me know the steps that you have followed. TIA.

[vrmerlin]

I finally got it to work. Here are the commands:

npm install --arch=x64 --msvs_version=2015 node_modules\.bin\electron-rebuild node node_modules\java\postInstall.js

@joeferner -- it looks like this is a bug in the java module. @MarshallOfSound found and fixed the problem here:

https://github.com/electron/electron/issues/8638#issuecomment-278807945

[dasarindam]

Continued to have same problem... Below are the command that I have ran after extracting the Electron-quick-start....

> npm install --arch=x64 --msvs_version=2015
> npm install electron-rebuild --save-dev
> npm install java
> node_modules\.bin\electron-rebuild
> node node_modules\java\postInstall.js

[yahyaKacem]

still having the same error here with windows 10, tried electron-quick-start as mentioned above with the steps provided by @dasarindam and others nothing changed. also tried generating a new app with electron-forge like this:

electron-forge init new-test-app
cd new-test-app
yarn start // or npm start

works, then followed the provided steps again:

npm install --arch=x64 --msvs_version=2015
npm install electron-rebuild --save-dev
npm install java
node_modules\.bin\electron-rebuild
node node_modules\java\postInstall.js
yarn start // or npm start

works, then add this line import { java } from 'java'; to the entry file src/index.js, and after yarn start again get the same error:

yarn start v0.22.0
$ electron-forge start
√ Checking your system
√ Locating Application
√ Preparing native dependencies: 1 / 1
√ Launching Application

App threw an error during load
Error: The specified module could not be found.
\\?\C:\Path\To\Project\new-test-app\node_modules\java\build\Release\nodejavabridge_bindings.node
    at process.module.(anonymous function) [as dlopen] (ELECTRON_ASAR.js:173:20)
    at Object.Module._extensions..node (module.js:598:18)
    at Object.module.(anonymous function) [as .node] (ELECTRON_ASAR.js:173:20)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (C:\Path\To\Project\new-test-app\node_modules\java\lib\nodeJavaBridge.js:21:16)
    at Object.<anonymous> (C:\Path\To\Project\new-test-app\node_modules\java\lib\nodeJavaBridge.js:316:3)

Also when running yarn make or yarn package the error appear when launching the app's installer and the make/packaging finish successfully. I checked the path to that file C:\Path\To\Project\new-test-app\node_modules\java\build\Release\nodejavabridge_bindings.node it does exist.

[dasarindam]

I tried building a new apps today. Its not building again.

1. -- was the build that i did 1st time and it still working
2. -- is the build I tried today. (See the version diff)
3. -- the version installed in my machine.

I also tried building with the Old config as (1) - But no luck though. Gettting error something like this.

C:\MyRD\Electron\electron-quick-start-master\DBClone\node_modules\java\lib\nodeJavaBridge.js:227 Uncaught Uncaught Error: Could not create class com.db.util.JavaTestPack java.lang.NoClassDefFoundError: com/db/util/JavaTestPack

The 227 of this js file is commented and TODO--- Not sure what might be the issue. var clazz = java.findClassSync(name); // TODO: change to Class.forName when classloader issue is resolved.

Hope to get a quick resolve...

[gpinkham]

Not sure if this is a valid solution but what I did after installing was running electron-rebuild I believe this does not run any postInstall steps so the build/jvm_dll_path.json file is missing.. I manually created it and all was well.
but this brings up an interesting issue I think Electron apps will have.. This is a build time location for Java.. not the location of Java on the client computer. It would mean the Electron app would only work if the same exact java version/build was installed (so the locations match). @joeferner am I understanding this correctly? I had thought about patching it to find Java at runtime.. but then the binding may not match (jdk 8 vs 9 etc..).