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From "Juozas Baliuka" <bali...@centras.lt>
Subject Re: [reflect] Proposal: (WAS [BeanUtils] etc...)
Date Sun, 16 Jun 2002 19:55:17 GMT

We can implement some reflection things too.
It is about code generation. Some ideas was discussed on BCEL list.
We have some code in simplestore, this code is not persistence specific and
can be used
for any aspects, simplestore and XORM on sourceforge uses it to implement
persistence aspect. This code generates interceptor/proxy/enhancer on the
fly in memory like
java.reflect.Proxy doe's.

> Ola,
>
> Perhaps I misunderstood what the proposal was all about.  My understanding
> was that it was after introspection rather than pure reflection.  When I
> hear the word "reflection", the list of features that comes to my mind is:
>
> 1. List of methods
> 2. List of constructors
> 3. List of fields
> 4. List of inner classes
>
> And that's about it - all of this is basically done by the JVM itself.
> Sure, we can put some veneer over it - but I thought this proposal called
> for something more.
>
> The word "introspection" is one level above reflection: beans, bean
> properties etc.  These may be implemented using reflection or not.  This
is
> where the diversity begins.  Pretty much everybody supports JavaBeans.
But
> then on top of that we all add our extensions: BeanUtils support
DynaClass,
> JXPath has JXPathBeanInfo, etc.  We are all expanding the notion of a Bean
> beyond the official JavaBean specification.  Strictly speaking, even Ant
> with its mapping of "foobar" to "getFooBar" is extending the
specification.
>
> There is a layer above introspection, which is abstract models and mapping
> those models to Java artifacts.  For example, there is a JSR that maps UML
> to EJB.  IMO, that stuff is much too abstract for our purposes. We don't
> want to end up with something like MOF, which is complex to the point of
> being almost esoteric.
>
> I am not convinced we can do anything about Java Reflection - it is built
> natively into the JVM.  Introspection though is a different matter.
>
> - Dmitri
>
>
> > >The multitude of potential users of this component is
> > >huge, they all have
> > >current solutions and they all have some peculiarities about them. For
> this
> > >new component to be successful, we will need to address all of those
> > >requirements, which calls for an abstract, configurable and
customizable
> > >architecture.
> >
> > I don\'t agree. Well, of course there are many users that do a lot of
> stuff in their reflection/introspection packages.
> >
> > But IMO reflect should be a mere utility for easy use of reflection
> (reducing complexity and awkwardness in java.lang.reflect). Other cool
> things (like automatic configuration of beans from command line or config
> files) do belong in other packages (both examples above should go in a
> Configuration framework?).
> >
> > Those are _users_ of reflection, they don\'t faciliate reflection in
> themselves. This doesn\'t call for plugable architectures, and if we end
up
> with it I believe that we have over-engineered them and missed a clean
> separation of concerns.
> >
> > I think of a Reflection class with static methods like
> >
> > Reflection.set( Object bean, String propertyName, Object value);
> >
> > Object o = Reflection.get( Object bean, String propertyName);
> >
> > Reflection.add( Object bean, String propertyName, Object value);
> >
> > Reflection.put( Object bean, String propertyName, Object key, Object
> value);
> >
> > Reflection.set( Object bean, String propertyName, int index, Object
> value);
> >
> > Object result = Reflection.call( Object bean, String methodName, Object
[]
> parameterValues);
> >
> > The internals of a Reflection class could very well use a plugable
> framework for insertion of new handy methods and cached lookup of
reflection
> Method objects (like all getters in a class etc), and some of this
> functionality should probably be pluggable (for people to insert new
> bean-like naming conventions, maybe using Predicate on methods).
> >
> > But main functionality exposed as handy methods.
> >
> > /O
> >
> > --------------------
> > ola.berg@arkitema.se
> > 0733 - 99 99 17
> >
> > --
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