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From Dmitri Plotnikov <dmi...@apache.org>
Subject Re: [BeanUtils][Betwixt][commons] [jxpath] Proposal: Reflection/Introspection/MetaData package
Date Sun, 16 Jun 2002 17:15:46 GMT
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 believe that before we can propose an architecture, we need to collect the
requirements. How about we start off by pulling together all of them into
one set of documents?   I will gladly contribute the "Introspection in
JXPath" chapter.

BTW, we'll need a name for this new thing.  How about Jin?

- Dmitri


----- Original Message -----
From: <costinm@covalent.net>
To: "Jakarta Commons Developers List" <commons-dev@jakarta.apache.org>
Sent: Sunday, June 16, 2002 11:55 AM
Subject: Re: [BeanUtils][Betwixt][commons] Proposal:
Reflection/Introspection/MetaData package


> See also o.a.tomcat.util.IntrospectionUtils :-)
>
> It also have a nice feature - it takes an args[], and using introspection
> calls the setters, using "-name value" or "-name", based on the method
> signatures - setName( boolean ) or setName( String/int/whatever )
> I personally find it very usefull - with a main() and 2 lines of code
> you can get a class that works as an Ant task or a bean or CLI.
>
> I would also count the axis introspection classes, and probably few
> others.
>
> Costin
>
>
> On 16 Jun 2002, Martin van den Bemt wrote:
>
> > Also check this with the ant team, who have a lot of introspection in
> > there code.. It works on all jdk versions afaik.
> > See o.a.tools.ant.Introspectionhelper.
> >
> > +1 on the idea btw..
> >
> > Mvgr,
> > Martin
> >
> > On Sun, 2002-06-16 at 13:40, Stephen Colebourne wrote:
> > > Hi,
> > > Currently, Betwixt and other users of BeanUtils rely on the java.beans
class
> > > Introspector to extract details from a class. Introspector is a very
old and
> > > limited class in todays terms:
> > > - it doesn't support collections, just simple objects and arrays
> > > - it doesn't support modern conventions such as addXxx() adds to a the
xxx
> > > list
> > > - it doesn't support overloading well
> > > - the bean info technique is difficult to code, poorly understood and
> > > limiting
> > > - it's just too plain dumb.
> > >
> > > I propose that BeanUtils/Betwixt/commons should replace Introspector
with a
> > > more general purpose reflection/introspection package. Architecturally
this
> > > would sit above reflection, but below Introspection:
> > >
> > > Requirements/Goals:
> > > - handle classes other than beans
> > > - support extensible metadata (not just for GUI builders)
> > > - handle normal (today) bean conventions (get/set/add/put methods)
> > > - handle future conventions that are not yet standard
> > > - support method overloading
> > > - be easily used directly from BeanUtils and Betwixt (and probably
others)
> > > - be a complete alternative to using java.lang.reflect
> > > - return immutable objects
> > >
> > > My proposed solution (not coded, fully open to discussion):
> > > Build a system with similarities to Digester. Rules get called when
the
> > > class is examined determine how to link the methods together. For
example
> > > the FindGetPropertyMethodRule would look at method names starting with
get
> > > etc. The rule then classifies the method as a GET method and stores it
into
> > > a structure something like this:
> > >
> > > - MethodSetInfo - holds details about a related set of methods.
> > > public String getName()
> > > public List getMethodInfos()
> > > public MethodInfo getMethodInfo(name)
> > > public Map getMetaData()
> > > public MetaData getMetaData(String name)
> > >
> > > - ClassInfo - main class that holds the representation of class.
Subclass of
> > > MethodSetInfo
> > > public List getMethodSetInfos()
> > > public MethodSetInfo getMethodSetInfo(name)
> > > public List getMethodSetInfos(methodSetType)
> > > public MethodSetInfo getMethodSetInfo(methodSetType, name)
> > > public PropertyInfo getPropertyInfo(name)  // convenience
> > >
> > > - PropertyInfo - subclass of MethodSetInfo for properties (Lists/Maps
etc.
> > > tbd)
> > > public Class getPropertyType()
> > > public MethodInfo getGetMethodInfo()  // convenience
> > > public MethodInfo getSetMethodInfo()  // convenience
> > > public Object getValue()
> > > public void setValue()
> > >
> > > - MethodInfo - categorised info about a method
> > > public String getName()
> > > public Method getMethod()
> > > publc String getCategory()
> > > public Map getMetaData()
> > > public MetaData getMetaData(String name)
> > > public Object invoke(object, args, respectAccessFlags)
> > >
> > > Attached to each element is the ability to hold MetaData. This is
> > > particularly important for Betwixt. It would allow the XMLBeanInfo
class to
> > > be held directly on the representation of the class. And I'm sure
other
> > > projects want MetaData - its supposed to be a long standing request
for J2SE
> > > (I know I need it for the Joda project).
> > >
> > > Note that I haven't expanded on the Rule part at the moment.
Basically,
> > > people must be able to write their own rules and add them to the
standard
> > > rules for beans.
> > >
> > > As for which project it belongs with...I suggest lang or something new
> > > (reflect?). I would like to extract it from BeanUtils because its not
Bean
> > > specific.
> > >
> > >
> > > Well, its an idea at the moment. There are some similarities to
DynaBeans,
> > > but I think it goes way further. I already have a partial version of
this,
> > > but its specific to my needs. It needs some rework anyway, so I
thought
> > > about if it could be generic. Opinions??
> > >
> > > Stephen
> > >
> > > PS. Three more possibilities for lang:
> > > Nameable
> > > MetaData
> > > Rule
> > >
> > >
> > >
> > > --
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> > >
> > >
> >
> >
> >
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