How to programmatically load librxtxSerial in Java

Question

I started to play with arduino an interfacing it with Java, it was pretty straightforward, but now I would like to programmatically load the librxtxSerial native lib, and I can't figure out. Since I'm on MacOS 64bit and use Java6 I used the following jnilib : http://blog.iharder.net/2009/08/18/rxtx-java-6-and-librxtxserial-jnilib-on-intel-mac-os-x/ as recommended here : http://arduino.cc/playground/Interfacing/Java

After that I tried to load it programmatically like this :

/**
  * Loads the jnilib
  */
public static void loadJniLib() {
    // loads the jnilib from the source folder "src/main/resources"
    URL url = Demo.class.getResource("/librxtxSerial.jnilib");
    try {
        System.load(url.getPath());
    }
    catch (UnsatisfiedLinkError unsatisfiedLinkError) {
        // native code library failed to load.
        unsatisfiedLinkError.printStackTrace();
    }
}

Which seems to works (at least does not throw an exception).

But when I call the CommPortIdentifier.getPortIdentifier(PORT_NAME); it throws the following exception:

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:1758)
    at java.lang.Runtime.loadLibrary0(Runtime.java:823)
    at java.lang.System.loadLibrary(System.java:1045)
    at gnu.io.CommPortIdentifier.<clinit>(CommPortIdentifier.java:83)
    at fr.free.mdwhatever.arduino.maven.Demo.initialize(Demo.java:57)
    at fr.free.mdwhatever.arduino.maven.Demo.main(Demo.java:102)

So I do not understand what's wrong, since it seems to be the right way to load it according to : http://docs.oracle.com/javase/6/docs/api/java/lang/System.html#load(java.lang.String)

Any idea?

PS : You can find the whole code here : https://gist.github.com/1853637 which works provided the rxtx jar is in the classpath and the native library location is defined (like this in Eclipse : http://www.eclipsezone.com/eclipse/forums/t49342.html)

score 0 · Answer 1 · answered Feb 17 '12 at 15:05

0

The simplest way to work with this is to set the java.library.path system property, for example on the commandline using -Djava.library.path=/usr/lib/jni.

As I recall, library loading is designed to fail if the library is not explicitly whitelisted. That, in turn, means that the library must be on the java.library.path.

answered Feb 17 '12 at 15:05

user268396

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Thanks for your comment, I also tried to programmatically modify the `java.library.path` by adding the folder containing my jnilib and calling `System.loadLibrary("librxtxSerial");` with no luck either. Still, I know the other possibilities I have, but I would like to do it programmatically. – xavier.seignard Feb 17 '12 at 16:02

How to programmatically load librxtxSerial in Java

1 Answers1