Package com.vaadin.flow.router

Class NavigationStartedEvent

java.lang.Object

java.util.EventObject

com.vaadin.flow.router.NavigationStartedEvent

All Implemented Interfaces:

Serializable

public class NavigationStartedEvent
extends EventObject

Event fired through the service event bus when the server starts handling a navigation for a UI, before any BeforeLeaveEvent or BeforeEnterEvent listener runs.

The event is meant for monitoring tools that time navigations or count them per route. Every started event is followed by exactly one NavigationEndedEvent for the same navigation, fired on the same thread when the handling has finished, whatever the outcome. A listener can therefore keep timing state in a ThreadLocal. Both events are fired on the request thread while the session is locked.

Only the outermost navigation is reported. The navigations that Flow runs while handling it are part of it and fire no events of their own: a forward or reroute, the redirect that adds or removes a trailing slash, and the rendering of an error view. The ended event tells which view was shown in the end.

Two cases fire no events at all, since they continue a navigation that has already been reported: resuming a postponed navigation with BeforeLeaveEvent.ContinueNavigationAction.proceed(), and showing a PreserveOnRefresh view once the browser has sent its window name.

The location and trigger are the ones requested, as they are before any forward or reroute.

Since:

25.4

See Also:

• NavigationEndedEvent
• Serialized Form

Field Summary

Fields inherited from class java.util.EventObject

source

Constructor Summary

Constructors

Constructor	Description
NavigationStartedEvent(UI ui, Location location, NavigationTrigger trigger)	Creates a new event.

Method Summary

Modifier and Type	Method	Description
Location	getLocation()	Gets the location that was requested, before any forward or reroute.
NavigationTrigger	getTrigger()	Gets the action that triggered the navigation, such as a page load, a click on a router link or a call to UI.navigate(String).
UI	getUI()	Gets the UI that navigates.

Methods inherited from class java.util.EventObject

getSource, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

NavigationStartedEvent

public NavigationStartedEvent(UI ui,
 Location location,
 NavigationTrigger trigger)

Creates a new event.

Parameters:

ui - the UI that navigates, not null

location - the requested location, not null

trigger - the action that triggered the navigation, not null

Method Details

getUI

public UI getUI()

Gets the UI that navigates.

Returns:

the UI, never null

getLocation

public Location getLocation()

Gets the location that was requested, before any forward or reroute.

Returns:

the requested location, never null

getTrigger

public NavigationTrigger getTrigger()

Gets the action that triggered the navigation, such as a page load, a click on a router link or a call to UI.navigate(String).

Returns:

the navigation trigger, never null