With Java 9 on the close horizon I thought it would be a good learning exercise to port some of my projects over to Java 9. In one of my projects I have dependencies for rxjava and rxjavafx
dependencies {
compile 'io.reactivex:rxjava:1.2.6'
compile 'io.reactivex:rxjavafx:1.0.0'
...
}
I want to create this project as a named-module. To do this I need to create a module-info.java
file and I need to specify the requirements for rxjava
and rxjavafx
here. However, these libs don't have any module info yet.
In order to work around this I've read that I need to create Automatic Modules. From what I understand, I need to rename the rxjava
and rxjavafx
jars to have a simple name and then list the jars in the --module-path
parameter. I then add a requires
directive in my module-info.java
with the jar names.
module com.foo.bar {
requires rxjavafx;
requires rxjava;
}
I wrote a gradle task to edit the jar names for me, and it appears to be working in most cases. It takes all the jars that need to be compiled and renames them to not include version-info or slashes. The files are then concatenated into a :
separated string:
tasks.withType(JavaCompile) {
delete { delete '/tmp/gradle' }
copy {
from configurations.compile + configurations.testCompile
into '/tmp/gradle'
rename '(.*)-[0-9]+\\..*.jar', '$1.jar'
rename { String fileName -> fileName.replace("-", "") }
}
options.compilerArgs += ['--module-path', fileTree(dir: '/tmp/gradle', include: '*.jar').getFiles().join(':')]
}
Naturally the rx
libraries share some of their package names... this however causes the compiler to spit back errors such as:
error: module reads package rx.subscriptions from both rxjava and rxjavafx
error: module reads package rx.schedulers from both rxjava and rxjavafx
error: module reads package rx.observables from both rxjava and rxjavafx
error: module rxjava reads package rx.subscriptions from both rxjavafx and rxjava
error: module rxjava reads package rx.schedulers from both rxjavafx and rxjava
error: module rxjava reads package rx.observables from both rxjavafx and rxjava
error: module rxjavafx reads package rx.subscriptions from both rxjava and rxjavafx
error: module rxjavafx reads package rx.schedulers from both rxjava and rxjavafx
error: module rxjavafx reads package rx.observables from both rxjava and rxjavafx
It seems like the only way to get around this issue would be to re-package the contents of rxjava
and rxjavafx
into a single jar and add that as a single module. This doesn't seem like a good solution though...
So my questions are:
Note: I've tried running this with standard java
/javac
and they cause the same issues. Also here is my java version:
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+140)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+140, mixed mode)
Am I using the new module system correctly?
Yes. What you are seeing is intended behavior, and this is because JPMS modules do not allow split packages.
In case you are not familiar with the term "split packages" it essentially means two members of the same package coming from two different modules.
For example:
com.foo.A (from moduleA.jar)
com.foo.B (from moduleB.jar)
What can I do about this error?
You have two options:
Do these dependencies prevent me from updating, or should I just wait for rx to update their libs?
Hopefully rx will eventually update their libs to not have split packages at some point in the future. Until then, my recommendation would be to just smash the two jars together into a single jar (option #2).