Java bindings are broken

[jgvictores]

Inspiration: https://github.com/roboticslab-uc3m/asibot-main/tree/d640e9962ef62765f7354612cfcb88ed5cb3ca25/bindings

[PeterBowman]

I started the fix-6-java-bindings branch and made some uncommitted progress, but this is beyond my SWIG skills. Python bindings are far easier to create since it's a dynamically typed language. A statically, strongly typed one as Java requires some knowledge about the JNI wrappers around the remote library, that is, YARP. In other words, I can't compile viewIRobotManager(yarp::dev::PolyDriver&) because of the public dependency on yarp::dev::PolyDriver.

This is how it looks like in asrob_yarp_devices.java (generated by SWIG):

package asrob_yarp_devices;

public class asrob_yarp_devices {
  public static IRobotManager viewIRobotManager(PolyDriver d) {
    long cPtr = asrob_yarp_devicesJNI.viewIRobotManager(PolyDriver.getCPtr(d));
    return (cPtr == 0) ? null : new IRobotManager(cPtr, false);
  }
}

Even if I smuggle a import yarp.PolyDriver somehow, there is no yarp.PolyDriver.getCPtr method anywhere, which means that SWIG is not aware of the intrinsics of YARP's bindings and how to treat them.

A few links I gathered while messing with this:

• https://stackoverflow.com/questions/32844420/swig-using-imported-external-type
• https://stackoverflow.com/questions/30407792/how-to-create-an-extension-to-already-wrapped-library-via-swig/30413268
• https://stackoverflow.com/questions/33625816/typemap-javaimports-doesnt-work-for-inner-c-class
• http://swig.10945.n7.nabble.com/Adding-missing-imports-to-Java-td4765.html
• https://stackoverflow.com/questions/16499202/swig-importing-generated-class-from-a-different-module-and-package-into-the-curr
• http://swig.org/Doc1.3/Typemaps.html#Typemaps
• http://swig.org/Doc1.3/Java.html#java_typemaps
• http://www.swig.org/Doc1.3/Java.html#java_directors_typemaps
• http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_code_typemaps
• https://stackoverflow.com/questions/2816046/simple-typemap-example-in-swig-java
• http://swig.org/Doc1.3/Java.html#typemap_examples
• https://stackoverflow.com/questions/29627691/how-to-pass-swig-generated-swigtype-p-type-as-parameter-in-java
• https://stackoverflow.com/questions/12856490/how-to-pass-a-value-to-a-function-when-the-value-is-swigtype
• https://stackoverflow.com/questions/11005123/how-do-i-convert-to-type-swigtype-p-void-in-swig-generated-java-bindings
• https://stackoverflow.com/questions/24166297/swig-java-how-to-add-a-method-to-a-swigtype-class
• http://www.swig.org/Doc1.3/Java.html#void_pointers
• https://stackoverflow.com/questions/26110908/swig-typemap-java-object

[jgvictores]

A q&d solution I've done in the past was essentially creating a duplicate of yarp.i (e.g. removing parts and changing module name), but including the new header. Not sure... perhaps the world has seen worse practices...

[PeterBowman]

Java example app (currently broken) at 306e108.