WEB : Wise reflection for generic handlers
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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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