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From "Henri Yandell (JIRA)" <>
Subject [jira] Commented: (EL-13) Boolean bean property not found due to Introspector limitation
Date Mon, 20 Aug 2007 12:21:30 GMT


Henri Yandell commented on EL-13:

Few thoughts on this one:

* Minor, but worth fixing. 
* Naming needs to change, ie: "findBooleanIsMethods".
* Needs a unit test.
* The header to each attachment does not allow us to apply the code.

The latter is a definite problem Joe, can't do much if the offered code says "No part of this
file should be copied or distributed".

> Boolean bean property not found due to Introspector limitation
> --------------------------------------------------------------
>                 Key: EL-13
>                 URL:
>             Project: Commons EL
>          Issue Type: Bug
>    Affects Versions: 1.0
>         Environment: Windows XP, Java 1.5.0_07-b03, Tomcat 5.5.17
>            Reporter: Joe Littlejohn
>             Fix For: 1.1
>         Attachments:,,,, 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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