HasUrlComponent#setParameter is invoked clicking on self-referencing links

The setParameter method of HasUrlComponent gets invoked even if the user is already in there; this means all the operations the method does with the parameter are executed again for the same component instance. For example:

public class MainLayout extends VerticalLayout implements RouterLayout {

    public MainLayout() {
        add(new RouterLink("One", Foo.class, 1);
        add(new RouterLink("Two", Foo.class, 2);
        add(new RouterLink("Three", Foo.class, 3);
    }
}

@Route(value = "foo", layout = MainLayout.class)
public class FooCard extends VerticalLayout implements HasUrlParamenter<Long> {

    @Override
    public void setParameter(BeforeEvent event, Long parameter) {
        composeLayoutFor(parameter);
    }
}

If the user is at /foo/1 and clicks on link “One”, composeLayoutFor is invoked for the same instance even if the location does not change, for example duplicating components that the method might add (which depends on the parameter value).

[pleku]

but the current implementation always reuses based on the code snippet referenced in the above comment.

Should probably also consider in https://github.com/vaadin/spring/issues/263 that it should be possible to always create a new view instance on navigation for Spring too. Maybe when prototype scope is used ?

[Legioth]

Making it configurable e.g. through the @Route annotation sounds like a good way to go. I guess the API would then be something like @Route(value = "foo", reuseInstance = false). Should preferably also take router layouts into account since those are also reused using the same mechanism.

I think the comment about Spring can be disregarded. The original router prototype implementation delegated the decision whether to reuse an instance or create a new one to Spring, but the current implementation always reuses based on the code snippet referenced in the above comment.