November 2004 Archives
Bizarre behaviour in PropertyDescriptor
Posted by mister__m on November 29, 2004 at 09:26 AM | Permalink
| Comments (6)
I've just found out the most bizarre bug I've ever come accross in my 5 years of experience with the Java platform. Let's suppose you have the following code:
import java.beans.*;
public class BizarreBean {
public static class B1 {
public String getProperty() {
return null;
}
}
public static class B2 extends B1 {
public String getProperty() {
return null;
}
}
public static void main(String[] args) throws Exception {
PropertyDescriptor[] pd = Introspector.getBeanInfo(B2.class)
.getPropertyDescriptors();
for (int i = 0; i < pd.length; i++) {
if (!pd[i].getName().equals("property")) {
continue;
}
System.out.println(pd[i].getReadMethod());
break;
}
}
}
Basically there are two JavaBean classes, B1 and B2. B2 extends B1 and override the getter method for property. BizarreBean.main(String[]) just retrieves an array of PropertyDescriptors from B2's BeanInfo instance and then print the read method for property. The output for this will be:
public java.lang.String BizarreBean$B2.getProperty()
But what happens if a setter is defined for property? If B1 and B2 are changed like this:
public static class B1 {
public String getProperty() {
return null;
}
public void setProperty(String property) {
}
}
public static class B2 extends B1 {
public String getProperty() {
return null;
}
public void setProperty(String property) {
}
}
Then the output becomes:
public java.lang.String BizarreBean$B1.getProperty()
What is the logic behind this? None. This is one of the most awkward bugs I've ever found in J2SE. Unless anyone is able to explain in a reasonable way why this is not bug (I seriously doubt anyone will be able to), I'll file a bug report in the bug parade.
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