If I open ptII/ptolemy/actor/lib/Sinewave.xml and save it, then
the VersionAttribute gets added:
<property name="_createdBy" class="ptolemy.kernel.util.VersionAttribute"
value="2.1-devel"/>
Unfortunately, if I then try to run a model that uses Sinewave.xml,
I get a clone not supported exception:
cxh@cooley 21% java -classpath $PTII ptolemy.actor.gui.MoMLSimpleApplication
ptolemy/moml/demo/modulation.xml
Error encountered in:
<entity name="carrier" class="ptolemy.actor.lib.Sinewave">
java.lang.CloneNotSupportedException: The field associated with CURRENT_VERSION could
not be automatically cloned because field is final. This can be caused if the field
is not defined in a public class.
at ptolemy.kernel.util.NamedObj.clone(NamedObj.java:450)
at ptolemy.kernel.util.Attribute.clone(Attribute.java:103)
at ptolemy.kernel.util.NamedObj.clone(NamedObj.java:377)
at ptolemy.kernel.Entity.clone(Entity.java:154)
at ptolemy.kernel.ComponentEntity.clone(ComponentEntity.java:125)
at ptolemy.kernel.CompositeEntity.clone(CompositeEntity.java:206)
at ptolemy.actor.CompositeActor.clone(CompositeActor.java:193)
at ptolemy.moml.MoMLParser._createEntity(MoMLParser.java:1917)
at ptolemy.moml.MoMLParser.startElement(MoMLParser.java:1127)
at com.microstar.xml.XmlParser.parseElement(XmlParser.java:945)
at com.microstar.xml.XmlParser.parseContent(XmlParser.java:1118)
at com.microstar.xml.XmlParser.parseElement(XmlParser.java:947)
at com.microstar.xml.XmlParser.parseDocument(XmlParser.java:496)
at com.microstar.xml.XmlParser.doParse(XmlParser.java:176)
at com.microstar.xml.XmlParser.parse(XmlParser.java:146)
at ptolemy.moml.MoMLParser.parse(MoMLParser.java:618)
at ptolemy.moml.MoMLParser.parse(MoMLParser.java:599)
at ptolemy.moml.MoMLParser.parse(MoMLParser.java:584)
at
ptolemy.actor.gui.MoMLSimpleApplication.<init>(MoMLSimpleApplication.java:96)
at ptolemy.actor.gui.MoMLSimpleApplication.main(MoMLSimpleApplication.java:149)
The problem is that VersionAttribute.CURRENT_VERSION is declared as:
public static final VersionAttribute CURRENT_VERSION;
static {
try {
CURRENT_VERSION = new VersionAttribute("2.1-devel");
} catch (Exception ex) {
throw new ExceptionInInitializerError(
"Failed to create CURRENT_VERSION: "
+ KernelException.stackTraceToString(ex));
}
}
The reason we have a blank final and a static body is because the
VersionAttribute constructor will throw an IllegalActionException if
the value of the argument is not properly format, so we can't do
public static final VersionAttribute CURRENT_VERSION =
new VersionAttribute("2.1-devel");
because we are not catching the exception
It looks like NamedObj.clone() was throwing the exception:
for (int i = 0; i < fields.length; i++) {
try {
// VersionAttribute has a final field
if (fields[i].get(newObject) instanceof Settable) {
fields[i].set(newObject,
newObject.getAttribute(fields[i].getName()));
}
} catch (IllegalAccessException e) {
// FIXME: This would be a nice
// place for exception chaining.
throw new CloneNotSupportedException(
"The field associated with "
+ fields[i].getName()
+ " could not be automatically cloned because "
+ e.getMessage() + ". This can be caused if "
+ "the field is not defined in a public class.");
}
I added a check to see if the field in question is final.
for (int i = 0; i < fields.length; i++) {
try {
> // VersionAttribute has a final field
> if ( !Modifier.isFinal(fields[i].getModifiers())
&& fields[i].get(newObject) instanceof Settable) {
fields[i].set(newObject,
newObject.getAttribute(fields[i].getName()));
}
} catch (IllegalAccessException e) {
// FIXME: This would be a nice
// place for exception chaining.
throw new CloneNotSupportedException(
"The field associated with "
+ fields[i].getName()
+ " could not be automatically cloned because "
+ e.getMessage() + ". This can be caused if "
+ "the field is not defined in a public class.");
}
This seems to work, and I added a test to VersionAttribute.tcl that
replicates this error by attempting to clone a VersionAttribute.
Oddly, ptjacl seems to have problems with static fields in clones.
In the example below, I clone a NamedObj, and I get get
the static fields of the master with java::info fields -static,
but not of the clone?
% set n [java::new ptolemy.kernel.util.NamedObj "my NamedObj"]
java0x11
% set nClone [$n clone]
java0x12
% java::info fields -static $n
COMPLETE CLASSNAME FULLNAME LINKS CONTENTS DEEP ATTRIBUTES
% java::info fields -static $nClone
%
I'm pretty sure the bug is in ptjacl. The java::field method has
a similar problem.
Comments?
BTW - Clone and final objects is covered in
http://developer.java.sun.com/developer/JDCTechTips/2001/tt0306.html
-Christopher
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