PropertyModel not easily extendable
-----------------------------------
Key: WICKET-1968
URL: https://issues.apache.org/jira/browse/WICKET-1968
Project: Wicket
Issue Type: Bug
Components: wicket
Affects Versions: 1.4-RC1
Reporter: Mathieu Carbou
We wanted to create a LodableDetacheableProeprtyModel like this:
public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
public DetachablePropertyModel(String expression) {
super(new LoadableDetachableModel<Object>() {
protected Object load() {
return DetachablePropertyModel.this.load();
}
}, expression);
}
protected abstract Object load();
}
But this is not possible. Since we cannot access a method of a not yest
instanciated class.
So we wanted to chang to this:
public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
public DetachablePropertyModel(String expression) {
super();
setChainedModel(new LoadableDetachableModel<Object>() {
protected Object load() {
return DetachablePropertyModel.this.load();
}
});
}
protected abstract Object load();
}
But the constructor of AbstractPropertyModel requires a model and also (and
here is the issue) check for null argument:
public AbstractPropertyModel(final Object modelObject)
{
if (modelObject == null)
{
throw new IllegalArgumentException("Parameter
modelObject cannot be null");
}
target = modelObject;
}
So the only way to bypass this was to call the super constructor like this:
public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
public DetachablePropertyModel(String expression) {
super(expression, expression);
setChainedModel(new LoadableDetachableModel<Object>() {
protected Object load() {
return DetachablePropertyModel.this.load();
}
});
}
protected abstract Object load();
}
By giving the expression to the super class, and giving the expression also as
the object, it works. But it is not correct...
I think a redesign of AbstractPropertyModel would be necessary: to use the
method setChainedModel on AbstractPropertyModel , we currently need to first
have the object instanciated with a non null model.... Which is not what we may
want...
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