Trouble with javaaddpath for a jar, it seems to load fine, but Matlab can't find classes inside...

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Nathan Ellingson 2018-11-16

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https://ww2.mathworks.cn/matlabcentral/answers/430322-trouble-with-javaaddpath-for-a-jar-it-seems-to-load-fine-but-matlab-can-t-find-classes-inside

评论： Julien 2020-11-25

So, I'm trying to add a WorldWind map to my matlab application, WorldWind is open source and written in java. I'm trying to implement this example in Matlab to start off

/*
 * Copyright (C) 2012 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration.
 * All Rights Reserved.
 */
import gov.nasa.worldwind.BasicModel;
import gov.nasa.worldwind.awt.WorldWindowGLCanvas;
import javax.swing.*;
/**
 * This example demonstrates the simplest possible way to create a WorldWind application.
 *
 * @version $Id: SimplestPossibleExample.java 1171 2013-02-11 21:45:02Z dcollins $
 */
public class SimplestPossibleExample extends JFrame
{
    public SimplestPossibleExample()
    {
        WorldWindowGLCanvas wwd = new WorldWindowGLCanvas();
        wwd.setPreferredSize(new java.awt.Dimension(1000, 800));
        this.getContentPane().add(wwd, java.awt.BorderLayout.CENTER);
        wwd.setModel(new BasicModel());
    }
    public static void main(String[] args)
    {
        java.awt.EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                JFrame frame = new SimplestPossibleExample();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}

To do this in eclipse the only thing I had to do was add worldwind.jar to my javaclasspath. So, to do this in matlab I'm trying to do this

function Plot_World_Wind()
    javaaddpath('C:\Users\Nellingson\Documents\Programs\worldwind-v2.1.0\worldwind.jar')
    import gov.nasa.worldwind.BasicModel;
    import gov.nasa.worldwind.awt.WorldWindowGLCanvas;
    import javax.swing.*
    h = figure;So
    jf = get(h, 'JavaFrame');
    jf = jf.fHG2Client.getWindow;
    
    wwd = gov.nasa.worldwind.awt.WorldWindowGLCanvas();
    wwd.setPreferredSize(java.awt.Dimension(1000, 800));
    jf.getContentPane().add(wwd, java.awt.BorderLayout.CENTER);
    wwd.setModel(BasicModel());
    
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jf.pack();
    jf.setVisible(true);
end

But when import gets callled, the classes inside worldwindwind.jar do not get found....

Error: File: Plot_World_Wind.m Line: 4 Column: 12
Arguments to IMPORT must either end with ".*" or else specify a fully qualified class name: "gov.nasa.worldwind.awt.WorldWindowGLCanvas" fails this
test.

I double chaecked to see that they are acutally inside that jar file. Then ran javap to ensure that the jar file was not compiled with a version of java that is too new.

javap -classpath worldwind.jar -verbose gov.nasa.worldwind.awt.WorldWindowGLCanvas | findstr major
  major version: 52

Which I believe is the same version matlab 2018a uses. Im completely new to calling java from matlab. I have only used it by following examples pretty closely. Here I'm guessing there is something very obvious that I'm missing. After loading worldwind.jar I checked my known classes like this...

[~,knownjavaclasses,~] = cellfun(@fileparts,[javaclasspath('-dynamic'); javaclasspath('-static')],'uniformoutput',false)

ant the ones I'm looking for arn't there. Any ideas of what to try?

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Nathan Ellingson 2018-11-16

So I noticed that I can acually load the other classes from worldwindow.jar, just not gov.nasa.worldwind.awt.WorldWindowGLCanvas... and one more gov.nasa.worldwind.awt.WorldWindowGLJPanel, which I assume is for the same reason.

Julien 2020-11-25

Hello Nathan,

Quite an old post but I am experiencing exactly the same problem with MATLAB realeases newer than R2014b. I managed to make it working on older realeases (at least R2012b). Have you found a solution to this problem ?

I think this could be due to a conflict of gluegen-rt.jar and jogl-all.jar libraries which are now embedded with MATLAB (in matlabroot/java/jarext) since R2014b. Moreover these gluegen-rt.jar and jogl-all.jar libraries on which depend worldwind java project require native libraires (ressources actually) gluegen-rt-natives-linux-amd64.jar and jogl-all-natives-linux-amd64.jar (in linux).

Thanks in advance for your help!

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