javax.faces.view.facelets.MetaTagHandler Maven / Gradle / Ivy
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package javax.faces.view.facelets;
/**
* Every kind of markup element in Facelets VDL
* that has attributes that need to take action on a JSF Java API artifact is
* associated with an instance of this class. This class is an abstraction to
* enable a rule based method for directing how different kinds of elements take
* different kinds of actions in the JSF Java API. For example, consider this
* markup:
*
*
* <h:inputText value="#{user.userid}"
* valueChangeListener="#{user.newUserId}" />
*
*
* This markup element corresponds to an instance of {@link
* javax.faces.component.html.HtmlInputText} in the view.
* HtmlImputText has a number of attributes that are to be exposed
* to the page author. HtmlInputText also implements
* {@link javax.faces.component.EditableValueHolder}, which extends
* {@link javax.faces.component.ValueHolder}. Each of these interfaces also
* expose a number of attributes to the page author.
*
*
* Facelets employes the strategy pattern to allow the manner in which all
* possible attributes are handled based on the nature of the JSF Java API
* artifact associated with the markup element.
*
*
* Subclasses override the {@link #createMetaRuleset} method to return a
* {@link MetaRuleset} instance encapsulating all the strategies for all the
* attributes that make sense for this particular markup element. The runtime
* calls the {@link #setAttributes(FaceletContext, Object)} method to cause
* those rules to be executed and applied.
*
*
*
* @since 2.0
*/
public abstract class MetaTagHandler extends TagHandler {
/**
* Stores the last type.
*/
private Class lastType = Object.class;
/**
* Stores the mapper.
*/
private Metadata mapper;
/**
* Constructor.
*
* @param config the tag configuration.
*/
public MetaTagHandler(TagConfig config) {
super(config);
}
/**
* Extend this method in order to add your own rules.
*
* @param type the type.
* @return the {@link MetaRuleset}.
*/
protected abstract MetaRuleset createMetaRuleset(Class type);
/**
* Invoking/extending this method will cause the results of the created
* MetaRuleset to auto-wire state to the passed instance.
*
* @param ctx the Facelet context.
* @param instance the instance.
*/
protected void setAttributes(FaceletContext ctx, Object instance) {
if (instance != null) {
Class type = instance.getClass();
if (mapper == null || !this.lastType.equals(type)) {
this.lastType = type;
this.mapper = this.createMetaRuleset(type).finish();
}
this.mapper.applyMetadata(ctx, instance);
}
}
}