[Kaffe] Bug in PropertyDescriptor, patch included.

Moses DeJong dejong at cs.umn.edu
Thu Feb 4 00:30:49 PST 1999

Hello all.

I seem to have run into another bug in the Bean classes. It seems 
that the name returned by PropertyDescriptor.getName() (this really
calls FeatureDescriptor.getName()) returns null. I took a look at
the FeatureDescriptor class and it seems like null will be returned
if FeatureDescriptor.setName() is not called.

Here is some code that shows the bug.

// Start file PropertyDescriptorBug.java

import java.lang.reflect.*;
import java.beans.*;
import java.util.*;

public class PropertyDescriptorBug {
    public static void main(String[] argv) throws Exception {

	Class cls = java.awt.Button.class;

	BeanInfo beanInfo = Introspector.getBeanInfo(cls);

	PropertyDescriptor descriptors[] = beanInfo.getPropertyDescriptors();
	for (int i = 0; i < descriptors.length; i++) {
	    if (descriptors[i] == null) {
		throw new NullPointerException("descriptor is null");
	    if (descriptors[i].getName() == null) {
		throw new NullPointerException("descriptor.getName() is null");

	    System.out.println("prop name is " + descriptors[i].getName());


// End file PropertyDescriptorBug.java

JDK output

prop name is enabled
prop name is actionCommand
prop name is foreground
prop name is label
prop name is visible
prop name is background
prop name is font
prop name is name

Kaffe output

% java PropertyDescriptorBug
java.lang.NullPointerException: descriptor.getName() is null
        at java/lang/Throwable.<init>(Throwable.java:37)
        at java/lang/Exception.<init>(Exception.java:21)
        at java/lang/RuntimeException.<init>(RuntimeException.java:21)
        at java/lang/NullPointerException.<init>(NullPointerException.java:21)
        at PropertyDescriptorBug.main(PropertyDescriptorBug.java:19)

Kaffe output with setName() patch

% kaffe PropertyDescriptorBug
prop name is minimumSize
prop name is peer
prop name is enabled
prop name is foreground
prop name is class
prop name is treeLock
prop name is preferredSize
prop name is focusTraversable
prop name is bounds
prop name is visible
prop name is toolkit
prop name is actionCommand
prop name is graphics
prop name is valid
prop name is label
prop name is maximumSize
prop name is doubleBuffered
prop name is locationOnScreen
prop name is name
prop name is font
prop name is cursor
prop name is background
prop name is alignmentY
prop name is parent
prop name is size
prop name is alignmentX
prop name is location
prop name is showing
prop name is locale

Now, I am not exactly sure that this is the "right" patch
but it seemed to cure my null name problem. There still seems to be
something wrong with the descriptors as a lot more descriptors
are returned in Kaffe then in the JDK.

% cvs diff -r1.1 PropertyDescriptor.java 
Index: PropertyDescriptor.java
RCS file: /home/cvspublic/kaffe/libraries/javalib/java/beans/PropertyDescriptor.java,v
retrieving revision 1.1
diff -u -r1.1 PropertyDescriptor.java
--- PropertyDescriptor.java     1998/07/14 17:02:00     1.1
+++ PropertyDescriptor.java     1999/02/04 09:28:39
@@ -28,6 +28,7 @@
 public PropertyDescriptor(String propertyName, Class beanClass, String getterName, String setterName) throws IntrospectionException
+        setName(propertyName);
        this.getter = null;
        this.setter = null;
        this.rettype = null;
@@ -51,6 +52,7 @@
 public PropertyDescriptor(String propertyName, Method getter, Method setter) throws IntrospectionException
+        setName(propertyName);
        this.getter = getter;
        this.setter = setter;
        rettype = null;

I hope that helps
Mo DeJong
dejong at cs.umn.edu

More information about the kaffe mailing list