Dfyjkt

I've developed a library which module-info.java looks like that:

module foo.bar 
 requires org.apache.commons.lang3;
 requires javafx.base;
 requires java.validation;
 exports foo.bar;

This library is used in another project where the module-info.java contains the following:

module other.project 
 requires org.apache.commons.lang3;
 requires javafx.base;
 requires javafx.graphics;
 requires javafx.fxml;
 requires foo.bar;

When I try to use import javafx.beans.value.WritableValue; I get the error

Package javafx.beans.value is declared in foo.bar, which does not
export it to module other.project.

UPDATE: I created two example projects which reproduce the problem. Please find them here to download.

I do not understand why that is and yet I could not find a solution.

Based on the project posted here, the error that you get when you open the project is:

Package 'javafx.beans.property' is declared in module 'com.example.external.lib', which does not export it to module 'example.project'

The reason for this error is that you are adding some packages from javafx.base to your external library, but those are not exported to the project that uses this library. The javafx.beans.property package is internally used by the external module, but it can't be exported.

So these are some proposed changes to make it work.

If you are creating a modular jar (using a module-info class) as a dependency for another project, you don't need to use the shadow plugin, and you don't need to bundle the JavaFX dependencies in your jars.

1. External-library project

So you can have the same module-info.java file:

module com.example.external.lib 
 requires javafx.base;
 requires org.apache.commons.lang3;

 exports com.example.external.library;

with a build.gradle like this:

buildscript 
 repositories 
 jcenter()
 

 dependencies 
 classpath 'com.google.gradle:osdetector-gradle-plugin:1.6.0'
 


apply plugin: 'com.google.osdetector'
apply plugin: 'java'

ext.platform = osdetector.os == 'osx' ? 'mac' : osdetector.os == 'windows' ? 'win' : osdetector.os

sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11

repositories 
 mavenCentral()


dependencies 
 compile 'org.apache.commons:commons-lang3:3.8.1'
 compile "org.openjfx:javafx-base:11:$platform"


compileJava 
 doFirst 
 options.compilerArgs = [
 '--module-path', classpath.asPath,
 '--add-modules', 'javafx.base'
 ]
 

Now, when you run gradle build, you will generate libs/external-library.jar, a 2 KB jar, without JavaFX dependencies.

Note that if you still want to do shadow jar with this external project, you can use compileOnly "org.openjfx:javafx-base:11:$platform" to keep the JavaFX dependencies out of this jar.

2. Project-using-external-lib

You can add that jar to the project.

build.gradle:

buildscript 
 repositories 
 jcenter()
 

 dependencies 
 classpath 'com.google.gradle:osdetector-gradle-plugin:1.6.0'
 


apply plugin: 'com.google.osdetector'
apply plugin: 'java'

ext.platform = osdetector.os == 'osx' ? 'mac' : osdetector.os == 'windows' ? 'win' : osdetector.os

sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11

repositories 
 mavenCentral()


dependencies 
 compile files('libs/external-library.jar')
 compile 'org.apache.commons:commons-lang3:3.8.1'
 compile "org.openjfx:javafx-base:11:$platform"


compileJava 
 doFirst 
 options.compilerArgs = [
 '--module-path', classpath.asPath,
 '--add-modules', 'javafx.base'
 ]
 

But now your module-info file should include again the javafx.base dependency:

module example.project 
 requires javafx.base;
 requires com.example.external.lib;

 exports com.example.project;

You can run gradle build to generate a jar, and IntelliJ won't complain anymore.

If you want to have a shadow jar at the end, you can also apply:

buildscript 
 repositories 
 mavenCentral()
 maven 
 url "https://plugins.gradle.org/m2/"
 
 
 dependencies 
 classpath 'com.google.gradle:osdetector-gradle-plugin:1.6.0'
 


apply plugin: 'application'
apply plugin: 'com.google.osdetector'

ext.platform = osdetector.os == 'osx' ? 'mac' : osdetector.os == 'windows' ? 'win' : osdetector.os

sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11

repositories 
 mavenCentral()


dependencies 
 compile files('libs/external-library.jar')
 compile 'org.apache.commons:commons-lang3:3.8.1'
 compile "org.openjfx:javafx-base:11:$platform"


compileJava 
 doFirst 
 options.compilerArgs = [
 '--module-path', classpath.asPath,
 '--add-modules', 'javafx.base'
 ]
 


run 
 doFirst 
 jvmArgs = [
 '--module-path', classpath.asPath,
 '--add-modules', 'javafx.base'
 ]
 


mainClassName = "com.example.project.PublicClass"

jar 
 manifest 
 attributes 'Main-Class': 'com.example.project.PublicClass'
 
 from 
 configurations.compile.collect it.isDirectory() ? it : zipTree(it) 
 

so you would be able to run java -jar build/libs/project-using-external-lib.jar. Note that this jar will contain the JavaFX classes.

Doing a shadow jar is not to the recommended way to distribute your project, but since you have automatic modules (commons-lang3) you can't use jlink, unless you convert that into an explicit module (see this answer).