Tobi McTobsen Tobi McTobsen - 1 month ago 33
Java Question

How to add native dependencies for Netty and RXTX in Gradle?

In my application I want to do some communication with an Arduino board. In order to realize the serial communication I want to use the Netty framework together with the RXTX transport library.



So I added the following lines to my Gradle build configuration:

dependencies {
compile group: 'io.netty', name: 'netty-all', version: '4.1.5.Final'
compile group: 'io.netty', name: 'netty-transport-rxtx', version: '4.1.5.Final'
...
}


Now the compile time dependencies are solved and I can build the project without any errors.

My build configuration generates an executable JAR as a result using the following commands:

jar {
manifest {
attributes 'Main-Class': 'de.project.Main',
'Implementation-Title': 'My Project',
'Implementation-Version': version
}
from {
configurations.compile.collect {
it.isDirectory() ? it : zipTree(it)
}
}
}


But because the RXTX library uses native libraries I get the following exception when I'm executing my code:

java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver
Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1864)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at gnu.io.CommPortIdentifier.<clinit>(CommPortIdentifier.java:83)
at de.project.communication.SerialConnector.getSerialPorts(SerialConnector.java:83)
at de.project.Main.main(Main.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)


The exception tells me that I need the platform dependent native libraries for RXTX, like:

librxtxSerial.jnilib (for OSX)

So my question is: What are the best practices for adding native libraries to my Gradle build? And how can I tell IntelliJ to use these native libraries as well, when running my project out of the IDE? I haven't found any satisfying answers on the internet so far.

Answer

I solved the problem now by using additional dependencies for the RXTX libraries:

I added the two dependencies:

dependencies {
  compile group: 'io.netty', name: 'netty-all', version: '4.1.5.Final'
  compile group: 'io.netty', name: 'netty-transport-rxtx', version: '4.1.5.Final'

  // New dependencies:
  compile group: 'org.bidib.jbidib', name: 'jbidibc-rxtx-2.2', version: '1.6.0'
  compile group: 'org.bidib.jbidib', name: 'bidib-rxtx-binaries', version: '2.2'

  ...
}

The library 'jbidibc-rxtx-2.2' uses another loading mechanism in order to load the binaries from 'bidib-rxtx-binaries'. That's why it works now.

Because 'netty-transport-rxtx' already provides the RXTX library as a dependency, I added the following configuration so that only the 'new' RXTX libraries are used in my project.

configurations {
  all*.exclude group: 'org.rxtx'
}