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, IQueueRegion, IHeaderContributor, IRequestableComponent, IHierarchical<Component>, 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:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	LAZY_LOAD_COMPONENT_ID Deprecated. will be removed in Wicket 9

Fields inherited from class org.apache.wicket.markup.html.panel.Panel

PANEL

Fields inherited from class org.apache.wicket.Component

ENABLE, FLAG_INITIALIZED, FLAG_RESERVED1, FLAG_RESERVED2, FLAG_RESERVED3, FLAG_RESERVED4, FLAG_RESERVED5, FLAG_RESERVED8, PARENT_PATH, PATH_SEPARATOR, RENDER, RFLAG_CONTAINER_DEQUEING, RFLAG_CONTAINER_HAS_REMOVALS

Constructor Summary

Constructors

Constructor and Description
AjaxLazyLoadPanel(String id) Constructor
AjaxLazyLoadPanel(String id, IModel<?> model) Constructor

Method Summary

Modifier and Type	Method and Description
abstract T	getLazyLoadComponent(String markupId) Factory method for creating the lazily loaded content that replaces the loading component after isContentReady() returns true.
Component	getLoadingComponent(String id) Create a loading component shown instead of the actual content until it is isContentReady().
protected Duration	getUpdateInterval() Get the preferred interval for updates.
protected void	handleCallbackScript(IHeaderResponse response, CharSequence callbackScript, Component component) Deprecated. this method is not called, and will be removed in Wicket 9
protected void	initTimer() Initialize a timer - default implementation installs an AbstractAjaxTimerBehavior on the page, if it is not already present.
protected boolean	isContentReady() Determines that the content we're waiting for is ready, typically used in polling background threads for their result.
protected boolean	isLoaded() Check whether the content is loaded.
protected void	onBeforeRender() Installs a page-global timer if not already present.
protected void	onComponentLoaded(Component component, AjaxRequestTarget target) Deprecated. override onContentLoaded(Component, Optional) instead - will be removed in Wicket 9
protected void	onConfigure() Called on all components before any component is rendered.
protected void	onContentLoaded(T content, Optional<AjaxRequestTarget> target) Called after the loading component was replaced with the lazy loaded content.
protected void	updateAjaxAttributes(AjaxRequestAttributes attributes) Deprecated. this method is not called, and will be removed in Wicket 9

Methods inherited from class org.apache.wicket.markup.html.panel.Panel

getRegionMarkup, newMarkupSourcingStrategy

Methods inherited from class org.apache.wicket.markup.html.WebMarkupContainer

getWebApplication, getWebPage, getWebRequest, getWebResponse, getWebSession

Methods inherited from class org.apache.wicket.MarkupContainer

add, addDequeuedComponent, addOrReplace, autoAdd, canDequeueTag, contains, dequeue, dequeue, dequeuePreamble, findChildComponent, findComponentToDequeue, get, getAssociatedMarkup, getAssociatedMarkupStream, getMarkup, getMarkupType, internalAdd, internalInitialize, iterator, iterator, newDequeueContext, onComponentTagBody, onDetach, onInitialize, onRender, queue, remove, remove, removeAll, renderAll, renderAssociatedMarkup, renderNext, replace, setDefaultModel, size, stream, streamChildren, toString, toString, visitChildren, visitChildren

Methods inherited from class org.apache.wicket.Component

add, addStateChange, beforeRender, canCallListener, canCallListenerAfterExpiry, checkComponentTag, checkComponentTagAttribute, checkHierarchyChange, clearOriginalDestination, configure, continueToOriginalDestination, createConverter, debug, detach, detachModel, detachModels, determineVisibility, error, exceptionMessage, fatal, findMarkupStream, findPage, findParent, findParentWithAssociatedMarkup, getAjaxRegionMarkupId, getApplication, getBehaviorById, getBehaviorId, getBehaviors, getBehaviors, getClassRelativePath, getConverter, getDefaultModel, getDefaultModelObject, getDefaultModelObjectAsString, getDefaultModelObjectAsString, getEscapeModelStrings, getFeedbackMessages, getFlag, getId, getInnermostModel, getInnermostModel, getLocale, getLocalizer, getMarkup, getMarkupAttributes, getMarkupId, getMarkupId, getMarkupIdFromMarkup, getMarkupIdImpl, getMarkupSourcingStrategy, getMetaData, getModelComparator, getOutputMarkupId, getOutputMarkupPlaceholderTag, getPage, getPageRelativePath, getParent, getPath, getRenderBodyOnly, getRequest, getRequestCycle, getRequestFlag, getResponse, getSession, getSizeInBytes, getStatelessHint, getString, getString, getString, getStyle, getVariation, hasBeenRendered, hasErrorMessage, hasFeedbackMessage, info, initModel, internalOnModelChanged, internalRenderComponent, internalRenderHead, isActionAuthorized, isAuto, isBehaviorAccepted, isEnableAllowed, isEnabled, isEnabledInHierarchy, isIgnoreAttributeModifier, isInitialized, isRenderAllowed, isRendering, isStateless, isVersioned, isVisibilityAllowed, isVisible, isVisibleInHierarchy, markRendering, modelChanged, modelChanging, onAfterRender, onComponentTag, onEvent, onModelChanged, onModelChanging, onReAdd, onRemove, redirectToInterceptPage, remove, remove, render, renderComponentTag, rendered, renderHead, renderPart, renderPlaceholderTag, replaceComponentTagBody, replaceWith, sameInnermostModel, sameInnermostModel, send, setAuto, setDefaultModelObject, setEnabled, setEscapeModelStrings, setFlag, setIgnoreAttributeModifier, setMarkup, setMarkupId, setMarkupIdImpl, setMetaData, setOutputMarkupId, setOutputMarkupPlaceholderTag, setParent, setRenderBodyOnly, setResponsePage, setResponsePage, setResponsePage, setVersioned, setVisibilityAllowed, setVisible, success, urlFor, urlFor, urlFor, urlForListener, urlForListener, visitParents, visitParents, warn, wrap

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.wicket.IQueueRegion

dequeue, newDequeueContext

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Detail

LAZY_LOAD_COMPONENT_ID

@Deprecated
public static final String LAZY_LOAD_COMPONENT_ID

Deprecated. will be removed in Wicket 9

See Also:

Constant Field Values

Constructor Detail

AjaxLazyLoadPanel

public AjaxLazyLoadPanel(String id)

Constructor

Parameters:

id -

AjaxLazyLoadPanel

public AjaxLazyLoadPanel(String id,
                         IModel<?> model)

Constructor

Parameters:

id -

model -

Method Detail

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

updateAjaxAttributes

protected final void updateAjaxAttributes(AjaxRequestAttributes attributes)

Deprecated. this method is not called, and will be removed in Wicket 9

handleCallbackScript

@Deprecated
protected final void handleCallbackScript(IHeaderResponse response,
                                                      CharSequence callbackScript,
                                                      Component component)

Deprecated. this method is not called, and will be removed in Wicket 9

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()

onComponentLoaded

@Deprecated
protected final void onComponentLoaded(Component component,
                                                   AjaxRequestTarget target)

Deprecated. override onContentLoaded(Component, Optional) instead - will be removed in Wicket 9

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

See Also:

MarkupContainer.addOrReplace(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()

Description copied from class: Component

Called on all components before any component is rendered. This method should be used to configure such things as visibility and enabled flags.

Overrides must call super.onConfigure(), usually before any other code

NOTE: Component hierarchy should not be modified inside this method, instead it should be done in Component.onBeforeRender()

NOTE: Why this method is preferrable to directly overriding Component.isVisible() and Component.isEnabled()? Because those methods are called multiple times even for processing of a single request. If they contain expensive logic they can slow down the response time of the entire page. Further, overriding those methods directly on form components may lead to inconsistent or unexpected state depending on when those methods are called in the form processing workflow. It is a better practice to push changes to state rather than pull.

NOTE: If component's visibility or another property depends on another component you may call other.configure() followed by other.isVisible() as mentioned in Component.configure() javadoc.

NOTE: Why should Component.onBeforeRender() not be used for this? Because if a component's visibility is controlled inside Component.onBeforeRender(), once invisible the component will never become visible again.

Overrides:

onConfigure in class Component

getUpdateInterval

protected 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

isLoaded

protected 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:

isContentReady()