Boolean bean property not found due to Introspector limitation
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Key: EL-13
URL: http://issues.apache.org/jira/browse/EL-13
Project: Commons EL
Issue Type: Bug
Affects Versions: 1.0 Final
Environment: Windows XP, Java 1.5.0_07-b03, Tomcat 5.5.17
Reporter: Joe Littlejohn
Attachments: AdditionalIntrospection.java, el_exception.txt
There is a bug in the java.beans.Introspector which means that it cannot find
the read method for a property of Boolean type (because it looks for the "get"
prefix, not the "is" prefix). This is arguably the expected behaviour of the
Introspector, however since the java.beans.PropertyDescriptor acts differently
(it can identify the property read method), this inconsistency hints it's a bug.
Also, with the advent of autoboxing, developers are supposed to be able to free
themselves from primitive types.
The commons EL library is affected by this bug, so using an interface like: -
public interface Bean {
Boolean isEnabled();
}
and an expression like: -
${bean.enabled}
fails with an ELException saying that the property could not be found (see
attached log snippet).
WebLogic does not suffer from this problem, presumably because they implement
their own EL parser (don't use commons.el) which doesn't use the Introspector. I
have written a suggested workaround for this problem which would allow the
commons.el library to continue its use of the Introspector, but deal with this
flaw (see attached). The AdditionalIntrospection could be used in the
BeanInfoManager.initialise() method, like so: -
PropertyDescriptor [] pds = mBeanInfo.getPropertyDescriptors ();
pds = AdditionalIntrospection.findMissingMethods(mBeanClass, pds); // new step
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