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From Jeremy Boynes <>
Subject Re: [POLL] API and Implementation serialization compatibility and upgrading
Date Wed, 18 May 2005 04:08:49 GMT
Beware email delays :-(

Dain Sundstrom wrote:
> On May 17, 2005, at 11:39 AM, David Jencks wrote:
>> As far as the form of metadata needed for an IOC container, I  
>> currently prefer GBeanInfo to the alternatives I am aware of.  I  
>> think it's important to specify exactly what interface is presented  
>> to the container, which IIUC spring does not require, and after  
>> working a lot with the jboss xmlbean implementation and writing the  
>> xdoclet xmlbeans plugin, I think that xml is perhaps the worst  choice 
>> possible, and javadoc tags not much better.
> Why not support all three?  We could provide a simple pluggable  
> interface to get the required metadata from store, be it GBeanInfo,  
> xml, annotations, etc.

Sure - as you know we designed the GBeanInfo so that it could easily be 
constructed from annotations when they were available (somewhere around 
4/24/05 on OSX IIRC). And I thought Hiram already had an XML to 
GBeanInfo generator.

GBeanInfo is, of course, "class" type metadata - it describes what 
attributes, references, etc. a GBean class has and not the values for 
any specific instance. That is why a static value (in JDK1.4) or 
annotations (in JDK1.5) are both good solutions as the GBeanInfo is 
fixed at the same time the class is compiled.

When the Configuration is built, its code dependencies tie it to a 
specific version of the class files in use (e.g. those from foo-1.0.jar) 
so the instance data will be reloaded back into compatible classes. 
Matching the configuration instance to a codebase that can be used to 
instantiate it is the ConfigurationManager's job.


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