:Notice: Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at. http://www.apache.org/licenses/LICENSE-2.0 . Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR  CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

[WARNING]
====
The default implementation of this service uses the HTTP session.
As the amount of data stored could potentially be quite large (for large numbers of users who use the app all day), it does in effect constitute a memory leak.

An alternative implementation might be more sophisticated (eg implementing an MRU/LRU queue, or using a NoSQL database to store the hints, or simply to disable the functionality altogether).
====


== See Also

* The xref:vw:ROOT:about.adoc[Web UI (Wicket viewer)] exposes the  xref:refguide:viewer:index/wicket/applib/mixins/Object_clearHints.adoc["clear hints"] mixin action
that is for use by end-users of the application to clear any UI hints that have accumulated for a domain object.

* Mutable view models should implement the xref:refguide:applib:index/services/hint/HintIdProvider.adoc[] in order for hints to work.

