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From "Java Developer (JIRA)" <>
Subject [jira] Commented: (CONFIGURATION-394) Providing BeanDiff(or ConfigurationDiff), BeanBatchUpdateListener, and some merge facility for Configuration(Specially for HierarchialConfiguration) to implement two-phase-commit-like protocol to alter entire configuration hierarchy in atomic manner.
Date Mon, 28 Dec 2009 05:28:29 GMT


Java Developer commented on CONFIGURATION-394:

Maybe some new project can come out from this model, however I've attached a zip file containing
a patch(i.e. some piece of code), that contains some classes:

1- BeanDiff class which models a bean difference between 2 java beans.
2- DiffHelper a helper class which actually computes bean diff.
3- Main class which contains a main() method that explain the way which I described about
weblogic mode.
4- You need XStream serializer also.

Inside com.test.bean.model package you find out 3 classes which are 3 simple java beans that
have reference to each other. Currently the java beans must extends AbstractSettableBean and
implements SettableBean interface. But with some extra code it is possible to remove such
a requirement.

I've not  tested it completely and I'm not sure it works correctly, however it brings a good
model for coding bean difference and configuration listeners.
Please start with main method and look at the way I've coded to achieve desired behavior.

I hope it helps.

> Providing BeanDiff(or ConfigurationDiff), BeanBatchUpdateListener, and some merge facility
for Configuration(Specially for HierarchialConfiguration) to implement two-phase-commit-like
protocol to alter entire configuration hierarchy in atomic manner.
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>                 Key: CONFIGURATION-394
>                 URL:
>             Project: Commons Configuration
>          Issue Type: Improvement
>            Reporter: Java Developer
>         Attachments:
>   Original Estimate: 2016h
>  Remaining Estimate: 2016h
> Sorry for English and for such a generic summary:
> If you have ever worked with Weblogic AdminConsole(Weblogic 10.3 in my case) you would
find out that it save your changes temporary and finally by clicking "Apply changes" it would
save all changes in configurations. If one of the changes is failed then Weblogic would rollback
all changes of configurations. Something like database transaction.
> The general idea could be that you create a clone of your entire or some parts of your
configuration hierarchy, then change the cloned version, and finally apply back the cloned
version on original version of hierarchy. Here when you ask the original configuration hierarchy
to accept new changes then the original hierarchy would compute the Diff between itself and
cloned version and deliver the changes to all listeners that have registered for configuration
changes. If any of listeners are not agree with new changes then all process of applying configuration
would be rolled back!
> Here in this scenario you need some facility to be added to Apache Commons Config and
also to Apache Commons BeanUtils:
> 1- A BeanDiff class( that can compute
the difference between two JavaBeans. These JavaBeans are custom classes that programmers
write for application configuration (e.g. CacheConfiguration class). These custom configuration
classes would use the apache common config classes to to store and retrieve the configuration
from any source. It can be extended to have ConfigurationDiff that would represent the changes
between two Configuration(shows which properties are altered)
> 2- Cloning entire hierarchy of configuration, I actually do not know whether currently
Apache Commons Config support this feature.
> 3- The most important part is adding some method to Configuration interface which enables
Configuration interface to accept a whole configuration hierarchy and then apply that hierarchy
to itself. The apply process consist of traversing the hierarchy and visiting each node, then
computing ConfigurationDiff for each node and then notifying the registered listeners of that
node for all updates that node has. If one of listeners reject the update then the process
would call rollback method of listeners.
> 4- Some class like ConfigurationUpdateListener(or BeanUpdateListener)  that has some
method like :
> public abstract void prepareUpdate(ConfigurationUpdateEvent updateevent)
>         throws ConfigurationUpdateRejectedException;
>     public abstract void activateUpdate(ConfigurationUpdateEvent updateevent)
>         throws ConfigurationUpdateFailedException;
>     public abstract void rollbackUpdate(ConfigurationUpdateEvent updateevent);
> All classes that are interested in configuration changes(batch changes not just one property
changes) can implement this class and register themselves in Configuration node in hierarchy.
> ------------------------------
> After some research! in Weblogic classes and jar files you can find the "com.bea.core.descriptor_1.4.0.0.jar"
in "BEA_HOME\modules" folder.
> After another research you can find some interesting classes like BeanUpdateListener,
BeanUpdateEvent, DescriptorBean, Descriptor inside "weblogic.descriptor" package. And also
another interesting class "weblogic.descriptor.internal.BeanDiff" class. Looking at  them
is useful!!
> I could not completely understand the model that Weblogic works but that point are what
I understood about it.
> I some useful features can be added to Apache Commons Config by looking at weblogic works.
It also can ease the process of writing ConfigurationMBeans for applications.

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