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https://issues.apache.org/jira/browse/LABS-161?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Simone Gianni resolved LABS-161.
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Resolution: Fixed
Magma is now completely generics aware, not only in the web part but also in
all the bindings, conversions and validations. Generics-aware convertors are
also possible.
The classes that parse the generics make up a rudimentary but functioning
library which could be contributed elsewhere (commons?)
> WEB : Wise reflection for generic handlers
> ------------------------------------------
>
> Key: LABS-161
> URL: https://issues.apache.org/jira/browse/LABS-161
> Project: Labs
> Issue Type: Improvement
> Components: Magma
> Reporter: Simone Gianni
> Assignee: Simone Gianni
>
> It would be nice to be able to define generic web handler and generic beans,
> the define non generic subclasses, and have Magma behave correctly with them.
> Magma uses reflection/introspection to determine data types in a number of
> situations :
> * Examining the type of properties in a bean to setup proper conversion
> * Examining the parameters of a do or handle method in a webhandler to
> perform proper conversion
> If a generic handler is defined, and then a non generic but parametrized
> subclass is defined, this subclass is, formally, using concrete classes and
> not generics.
> Suppose the following :
> public class DisplayingBeanHandler<T> extends WebHandler {
> public HtmlProducer doShow(T bean) {
> ...
> }
> }
> public class DisplayPersonHandler extends DisplayingBeanHandler<Person> {}
> DisplayPersonHandler? has a doShow(Person) method, at any effect.
> Unfortunately, to keep compatibility, the Java compiler will instead create a
> synthetic method based on Object :
> public class DisplayPersonHandler extends DisplayingBeanHandler<Person> {
> // Injected by compiler
> public HtmlProducer doShow(Object bean) {
> super.doShow((Person)bean);
> }
> }
> While this ensures proper checks, reflection will see this method as using
> Object, so Magma will not know what to convert it to.
> Where this happen, Magma has to correctly check for generics, and behave
> correctly.
> Since there are many places (and many more in the future) requiring this kind
> of functionality, a small "library" should be created to ease this pain.
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