Service Init Listener
VaadinServiceInitListener
can be used to configure RequestHandler
, IndexHtmlRequestListener
and DependencyFilter objects.
You can also use it to dynamically register routes during application startup, and to register session and UI listeners.
The listener gets a ServiceInitEvent
, which is sent when a Vaadin service is initialized.
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 Boot project, it’s sufficient to register this listener by adding the @Component
annotation on the class.
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 file should look like this:
com.mycompany.ApplicationServiceInitListener
Tip
| See https://docs.oracle.com/javase/tutorial/ext/basics/spi.html#register-service-providers and https://docs.oracle.com/javase/7/docs/api/java/util/ServiceLoader.html for details of Java SPI loading. |
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