Service Init Listener
The ServiceInitEvent
is fired when your Vaadin application starts. It’s a good place to configure the RequestHandler
, IndexHtmlRequestListener
and DependencyFilter
objects. You can also use it to dynamically register routes during application startup, and to register session and UI listeners.
In Spring and CDI applications, the ServiceInitEvent
is fired as an application event. It’s enough to annotate your bean method accepting ServiceInitEvent
as a parameter with the @EventListener
(Spring) or @Observes
(CDI) annotation. The following shows an example of this:
@Component
public class MyBean {
@EventListener
public void logSessionInits(ServiceInitEvent event) {
event.getSource().addSessionInitListener(
sessionInitEvent -> LoggerFactory.getLogger(getClass())
.info("A new Session has been initialized!"));
}
}
Alternatively, you can implement the VaadinServiceInitListener
interface and register it, like shown in the following example:
public class ApplicationServiceInitListener
implements VaadinServiceInitListener {
@Override
public void serviceInit(ServiceInitEvent event) {
event.addIndexHtmlRequestListener(response -> {
// IndexHtmlRequestListener to change the bootstrap page
});
event.addDependencyFilter((dependencies, filterContext) -> {
// DependencyFilter to add/remove/change dependencies sent to
// the client
return dependencies;
});
event.addRequestHandler((session, request, response) -> {
// RequestHandler to change how responses are handled
return false;
});
}
}
In a Spring or CDI project, all beans implementing the VaadinServiceInitListener
interface are registered automatically.
In plain Java projects, the listener should be registered as a provider via the Java Service Provider Interface (SPI) loading facility. To do this, you should create the META-INF/services
resource directory and a provider configuration file with the name com.vaadin.flow.server.VaadinServiceInitListener
. This is a text file and should contain the fully qualified name of the ApplicationServiceInitListener
class on its own line. It allows the application to discover the ApplicationServiceInitListener
class, instantiate it and register it as a service init listener for the application.
The content of the configuration file should look like this, as an example (replace com.mycompany
with the package name of your implementation):
com.mycompany.ApplicationServiceInitListener
The following pages offer more details about Java SPI loading:
EA8B92C9-D967-4C55-B760-FEBEEA964D72