Package com.vaadin.flow.server.communication

Class HeartbeatHandler

java.lang.Object

com.vaadin.flow.server.SynchronizedRequestHandler

com.vaadin.flow.server.communication.HeartbeatHandler

All Implemented Interfaces:

RequestHandler, SessionExpiredHandler, Serializable

public class HeartbeatHandler
extends SynchronizedRequestHandler
implements SessionExpiredHandler

Handles heartbeat requests. Heartbeat requests are periodically sent by the client-side to inform the server that the UI sending the heartbeat is still alive (the browser window is open, the connection is up) even when there are no UIDL requests for a prolonged period of time. UIs that do not receive either heartbeat or UIDL requests are eventually removed from the session and garbage collected.

For internal use only. May be renamed or removed in a future release.

Since:

1.0

Author:

Vaadin Ltd

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
HeartbeatHandler()

Method Summary

Modifier and Type	Method	Description
protected boolean	canHandleRequest(VaadinRequest request)	Check whether a request may be handled by this handler.
boolean	handleSessionExpired(VaadinRequest request, VaadinResponse response)	Called when the a session expiration has occurred and a notification needs to be sent to the user.
boolean	synchronizedHandleRequest(VaadinSession session, VaadinRequest request, VaadinResponse response)	Handles a heartbeat request for the given session.

Methods inherited from class com.vaadin.flow.server.SynchronizedRequestHandler

handleRequest

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.vaadin.flow.server.RequestHandler

handleRequest

Constructor Details

HeartbeatHandler

public HeartbeatHandler()

Method Details

canHandleRequest

protected boolean canHandleRequest(VaadinRequest request)

Description copied from class: SynchronizedRequestHandler

Check whether a request may be handled by this handler. This can be used as an optimization to avoid locking the session just to investigate some method property. The default implementation just returns true which means that all requests will be handled by calling SynchronizedRequestHandler.synchronizedHandleRequest(VaadinSession, VaadinRequest, VaadinResponse) with the session locked.

Overrides:

canHandleRequest in class SynchronizedRequestHandler

Parameters:

request - the request to handle

Returns:

true if the request handling should continue once the session has been locked; false if there's no need to lock the session since the request would still not be handled.

synchronizedHandleRequest

public boolean synchronizedHandleRequest(VaadinSession session,
 VaadinRequest request,
 VaadinResponse response)
                                  throws IOException

Handles a heartbeat request for the given session. Reads the GET parameter named ApplicationConstants.UI_ID_PARAMETER to identify the UI. If the UI is found in the session, sets it heartbeat timestamp to the current time. Otherwise, writes a HTTP Not Found error to the response.

Specified by:

synchronizedHandleRequest in class SynchronizedRequestHandler

Parameters:

session - The session for the request

request - The request to handle

response - The response object to which a response can be written.

Returns:

true if a response has been written and no further request handlers should be called, otherwise false

Throws:

IOException - If an IO error occurred

See Also:

• SynchronizedRequestHandler.handleRequest(VaadinSession, VaadinRequest, VaadinResponse)

handleSessionExpired

public boolean handleSessionExpired(VaadinRequest request,
 VaadinResponse response)
                             throws IOException

Description copied from interface: SessionExpiredHandler

Called when the a session expiration has occurred and a notification needs to be sent to the user. If a response is written, this method should return true to indicate that no more SessionExpiredHandler handlers should be invoked for the request.

Specified by:

handleSessionExpired in interface SessionExpiredHandler

Parameters:

request - The request to handle

response - The response object to which a response can be written.

Returns:

true if a response has been written and no further request handlers should be called, otherwise false

Throws:

IOException - If an IO error occurred