Module org.apache.wicket.extensions
Package org.apache.wicket.extensions.ajax.markup.html

Class AjaxLazyLoadPanel<T extends Component>

java.lang.Object
org.apache.wicket.Component
org.apache.wicket.MarkupContainer
org.apache.wicket.markup.html.WebMarkupContainer
org.apache.wicket.markup.html.panel.Panel
org.apache.wicket.extensions.ajax.markup.html.AjaxLazyLoadPanel<T>
All Implemented Interfaces:
Serializable, Iterable<Component>, IEventSink, IEventSource, IFeedbackContributor, IConverterLocator, IMetadataContext<Serializable,Component>, IQueueRegion, IHeaderContributor, IRequestableComponent, org.apache.wicket.util.IHierarchical<Component>, org.apache.wicket.util.io.IClusterable
public abstract class AjaxLazyLoadPanel<T extends Component> extends Panel
A panel which load lazily a single content component. This can be used if you have a component that is pretty heavy in creation and you first want to show the user the page and then replace the panel when it is ready.

This panel will wait with adding the content until isContentReady() returns true. It will poll using an AbstractAjaxTimerBehavior that is installed on the page. When the component is replaced, the timer stops. When you have multiple AjaxLazyLoadPanels on the same page, only one timer is used and all panels piggyback on this single timer.

This component will also replace the contents when a normal request comes through and the content is ready.

Since:
1.3
See Also:

  • Constructor Details

  • Method Details

    • isContentReady

      protected boolean isContentReady()
      Determines that the content we're waiting for is ready, typically used in polling background threads for their result. Override this to implement your own check.

      This default implementation returns true, i.e. assuming the content is ready immediately.

      Returns:
      whether the actual content is ready

    • getLoadingComponent

      public Component getLoadingComponent(String id)
      Create a loading component shown instead of the actual content until it is isContentReady().
      Parameters:
      id - The components id
      Returns:
      The component to show while the real content isn't ready yet

    • getLazyLoadComponent

      public abstract T getLazyLoadComponent(String markupId)
      Factory method for creating the lazily loaded content that replaces the loading component after isContentReady() returns true. You may call setRenderBodyOnly(true) on this component if you need the body only.
      Parameters:
      markupId - The components markupid.
      Returns:
      the content to show after isContentReady()

    • onContentLoaded

      protected void onContentLoaded(T content, Optional<AjaxRequestTarget> target)
      Called after the loading component was replaced with the lazy loaded content.

      This default implementation does nothing.

      Parameters:
      content - The lazy loaded content
      target - optional Ajax request handler

    • onBeforeRender

      protected void onBeforeRender()
      Installs a page-global timer if not already present.
      Overrides:
      onBeforeRender in class Component

    • initTimer

      protected void initTimer()
      Initialize a timer - default implementation installs an AbstractAjaxTimerBehavior on the page, if it is not already present.

    • onConfigure

      protected void onConfigure()
      Overrides:
      onConfigure in class Component

    • getUpdateInterval

      public Duration getUpdateInterval()
      Get the preferred interval for updates.

      Since all LazyLoadingPanels on a page share the same Ajax timer, its update interval is derived from the minimum of all panel's update intervals.

      Returns:
      update interval, must not be null

    • isLoaded

      public final boolean isLoaded()
      Check whether the content is loaded.

      If not loaded already and the content is ready, replaces the lazy loading component with the lazily loaded content.

      Returns:
      true if content is loaded
      See Also: