[Springframework-developer] Confusing NotWritablePropertyException for invalid bean property

[Jeremy H. <jh...@fa...>]

I have had an issue where a spring configured property is "set" with a
more specific type than the getter-method returns.  The reason is that
the getter method implements an interface and is required to return a
specific type.  The net result is that the getter and setter method take
in/return different class types.  My getter and setter looked like the
code below:

    public Component getView() {
        return view;
    }


    public void setView( Container view ) {
        this.view = view;
    }


This is probably not legal, JavaBeans style access, and my solution
ended up being renaming the method in the interface.  However, the error
message I received was confusing at best, since the property "view" is
obviously writeable based on the code pasted above.  The error message
was:

org.springframework.beans.factory.BeanCreationException: Error creating
bean with name 'alarmBanner' defined in class path resource
[default.dynapp.spring.xml]: Error setting property values; nested
exception is org.springframework.beans.NotWritablePropertyException:
Invalid property 'view' of bean class [AlarmBannerController]: Property
'view' is not writable
org.springframework.beans.NotWritablePropertyException: Invalid property
'view' of bean class [AlarmBannerController]: Property 'view' is not
writable
	at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:666)
	at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:588)
	at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:720)
	at org.springframework.beans.BeanWrapperImpl.setPropertyValues(BeanWrapperImpl.java:747)
	at org.springframework.beans.BeanWrapperImpl.setPropertyValues(BeanWrapperImpl.java:736)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:797)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:637)

The getter was not even required for spring, as I only set this
property.

I have two questions:
1) Is this behavior desirable?  Should Spring throw an exception if the
getter and setter's class type does not match.  This is probably not
really valid JavaBean-style properties, but obviously you can still get
and set the "view" property.  In my case, I was not even "getting" the
property using spring, but only setting it.

2) If this is the desired behavior, should the error message displayed
be clearer?  I have seen this error in the past and it usually means
that there is no setter method or the setter method had non-public
access.  It seems like this error message should read more like
"Property 'view' is not a valid bean property."  - or something like
that.


Jeremy Haile