macOS: how to install JavaFX properly to run mqtt-spy? - macos

Question

I'm trying to run mqtt-spy-1.0.0.jar on my macOS 10.14 system but it won't start, returning the following error message:
According to the developers, this problem is caused if JavaFX is missing on the system.
The latest version of the Oracle JDK is installed on my system as can be seen below, however, I'm aware that Oracle has excluded JavaFX from the JDK in v11.
So I downloaded JavaFX from GluonHQ and followed their instructions on how to get started.
Despite having both required variables set correctly in ~/.bash_profile, mqtt-spy-1.0.0.jar is still returning the error message shown on the first screenshot ...
What else do I need to do or what do I need to do differently to run mqtt-spy?

Answer 1

There is already an issue filed about this, but not a solution.
I haven't really tried to get it fully working, but these are the required steps to run a jar on Java 11 that requires JavaFX 11, but doesn't bundle it:
Go to OpenJFX docs and read about how to get started with JavaFX 11.
Download JavaFX 11 for your platform from here. Unzip it
Providing that you have Java 11 installed, and set as JAVA_HOME:
With mqtt-spy-1.0.0.jar (as latest release), you can run:
java --module-path /path-to/javafx-sdk-11.0.1/lib \
--add-modules javafx.controls,javafx.fxml -jar mqtt-spy-1.0.0.jar
After you run this, you will get this exception:
Exception in Application start method
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
...
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
Since Java 9, JAXB is not part of the JDK either. So you can add try to download the dependency from here) and add it to the classpath. But this will take some iterations (there are a few other required jars more, see this).
So why don't you use the latest snapshot available, that includes dependencies: mqtt-spy-1.0.1-beta-b18-jar-with-dependencies.jar.
With this:
java --module-path /path-to/javafx-sdk-11.0.1/lib \
--add-modules javafx.controls,javafx.fxml -jar mqtt-spy-1.0.1-beta-b18-jar-with-dependencies.jar
I get:
Warning: But this doesn't mean that the app will fully work. Given that it is a Java 8 app, there are things that have changed in JavaFX 11, mainly related to the control skins. If the app was using private API (com.sun.javafx....), that won't work now, because either it has been moved to public packages, or because it is not accessible by the modules. For the latter you can use --add-opens, but for the former there is no solution other than update the app dependencies to Java 9+.