Re: [Springframework-developer] Bean Inheritance

[Colin S. <col...@ex...>]

Colin Sampaleanu wrote:

> Colin Sampaleanu wrote:
>
>> Rob Harrop wrote:
>>
>>>    Reading through the 1.1 docs it says that a parent bean can never 
>>> be accessed directly in an app either through <ref> or getBean() yet 
>>> I was able to do both. Is this an error in the doc or the code?
>>>
>>> Rob
>>
>>
>>
>> This is prefaced with the text 'In the case that the parent 
>> definition does not specify a class' before the sample...
>>
>> If it has a class, it's usable as its own bean, and in fact you need 
>> to make it lazy-init=true or singleton=true to stop the factory from 
>> pre-instantiating it. I need to update the docs to specifically 
>> mention that.
>
>
> We could consider an 'abstract' attribute actually, to stop a bean 
> from ever being instantiated...

I've clarified the text a bit in the manual:

"""
In the case that the parent definition does not specify a class:

   ... a sample here with no class set

the parent bean can not get instantiated on its own; it's just a pure 
template or abstract bean definition that serves as parent definition 
for children. Trying to use such parent beans on it's own (by referring 
to it as a ref property of another bean, or doing an explicit getBean() 
call with the parent bean id, will result in an error. Similarly, the 
container's internal /preInstantiateSingletons/ method will completely 
ignore bean definitions which don't have either a parent or class 
attribute set, since they are not complete.

/Important Note/: there is no way to explicitly declare a bean 
definition as abstract. As described above, if the definition does not 
have a class specified, then it is effectively be considered abstract, 
will not be pre-instantiated, and can not be instantiated at all (by the 
user). If the bean does have a class definition, then it can be 
instantiated. As well, XmlBeanFactory will by default pre-instantiate 
all singletons; so it is important that if you have a (parent) bean 
definition to be used only as a template, which specifies its class, and 
do not want the container to pre-instantiate it, you must make sure to 
set the /lazy-init/ attribute to /true/.
"""

Colin