Greetings,
I am trying to create a data object (what C++ would call a struct) that is
passed between one plugin (Copy_N_Paste) to another plugin
(Fuzzy_C_Means). Copy_N_Paste uses it without issue, but Fuzzy_C_Means has
a class load runtime issue. Is there something that I need to do special
since ij is using its own class loader?
I am getting this runtime error that is perplexing me:
zoomData=ZoomData@160483c5
Target class loader: ij.io.PluginClassLoader@18a36070
ImageJ 1.54p; Java 21.0.3 [64-bit]; Linux 6.8.9-100.fc38.x86_64; 1665MB of
4096MB (40%)
java.lang.ClassCastException: class ZoomData cannot be cast to class
ZoomData (ZoomData is in unnamed module of loader ij.io.PluginClassLoader
@289dbc6; ZoomData is in unnamed module of loader ij.io.PluginClassLoader
@18a36070)
at Fuzzy_C_Means.goBackHome(Fuzzy_C_Means.java:1426)
ZoomData is a defined in the file ZoomData.jave in plugins directory (see
below).
Line Fuzzy_C_Means.java:1426 contains "Object class loader: ":
=====
IJ.log("zoomData="+zoomMap.get(title));
//IJ.log("mag="+zoomMap.get(title).mag);
if (zoomMap.get(title) != null) {
IJ.log("Target class loader: " + ZoomData.class.getClassLoader());
IJ.log("Object class loader: " +
zoomMap.get(title).getClass().getClassLoader());
}
if (zoomMap.containsKey(title))
Copy_N_Paste.setZoom(imp,zoomMap.get(title));
=====
The last line is what originally raised the issue. The 'if' statement was
added due to google suggesting that this is due to more than one class
loader and/or class definitions:
====
The java.lang.ClassCastException with the same class name but different
PluginClassLoader instances indicates that you have duplicate copies of
the ZoomData class in your application's classpath, and an object created
by one classloader is being cast to the type loaded by the other. In Java,
classes loaded by different classloaders are considered different types,
even if they have the same name and bytecode.
This scenario is common in environments that use modular classloaders,
such as plugin systems like those found in ImageJ (implied by
ij.io.PluginClassLoader)
====
There does not seem to be any runtime issue for Fuzzy_C_Means when placing
instances of ZoomData into the TreeMap:
====
TreeMap<String,ZoomData> zoomMap = new TreeMap<String,ZoomData>();
zoomMap.put(imp.getTitle(), new ZoomData(imp));
====
==== ZoomData.java ====
import ij.*;
import ij.process.*;
import ij.gui.*;
import java.awt.*;
import ij.plugin.*;
import ij.plugin.frame.*;
public class ZoomData {
public Rectangle srcRect = null;
public Insets insets = null;
public int sliderHeight = 0;
public double mag = Double.NaN;
private ZoomData() {}
public ZoomData(Rectangle sr, Insets i, int sh, double m) {
srcRect = sr;
insets = i;
sliderHeight = sh;
mag = m;
}
public ZoomData(ImagePlus imp) {
insets = imp.getWindow().getInsets();
srcRect = imp.getCanvas().getSrcRect();
mag = imp.getCanvas().getMagnification();
sliderHeight = imp.getWindow().getSliderHeight();
}
}
====
Thanks in advance,
Fred
--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html
