Thanks to the clues obtained from code in the OpenSecurityController project I am making some
serious progress in handling the Vaadin OSGi situation.
The one sticking point now is related to creating the instances of PROTOTYPE
services.
In the code below, when the component is activated the ComponentServiceObjects factory is not null.
When it comes to create the instance the factory is null.
How should this be handled?
@Component(service=QUIProvider.class)
public class QUIProvider extends UIProvider {
@Reference(scope=ReferenceScope.PROTOTYPE)
ComponentServiceObjects<QMainSiteUI> factory;
@SuppressWarnings("unchecked")
@Override
public Class<? extends UI> getUIClass(UIClassSelectionEvent event) {
return (Class<? extends UI>) QMainSiteUI.class;
}
@Override
public UI createInstance(UICreateEvent event) {
QMainSiteUI mainSiteUI = this.factory.getService();
UI ui = (UI) mainSiteUI;
ui.addComponentDetachListener(x -> factory.ungetService(mainSiteUI));
return ui;
}
}
Thanks,
Paul Fraser
On 28/06/2018 7:49 PM, Tim Ward wrote:
Hi Paul,
I’m glad to hear that this is working. It does look like it could use a little tidying up though.
The overall approach seems similar to that used in the OpenSecurityController project, although
that is even more decomposed into services, and might be a better model follow up.
* The UI instance is provided as a service
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/ui/UiServlet.java#L59>
using
a provider
* The UI provider uses Prototype scope service instances
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/MainUIProvider.java#L34>
to
create a UI instance per session. These are released when the UI detaches
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/MainUIProvider.java#L45>
* The UI then uses Prototype scope service instances to create views
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/MainUI.java#L138>
and
passes them to a view provider
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/MainUI.java#L195>.
The view provider ensures the view service is released when it is detached
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/OSCViewProvider.java#L63>
This model allows an incredibly flexible UI to be built entirely from OSGi services, right down to
the views. This means that the individual view instances can be DS components, and therefore
simply injected with business services
<https://github.com/opensecuritycontroller/osc-core/blob/534d035033804d360bd6fc253eaad4cda49a2d59/osc-ui/src/main/java/org/osc/core/broker/view/ApplianceView.java>.
This saves you from having huge hellish constructors, and from having a UI component that has all
the dependencies for every one of its views.
I hope this helps to demonstrate some of the awesome power that you can get from leveraging the
OSGi service model.
Best Regards,
Tim
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