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 {
private Class lastType = Object.class;
private Metadata mapper;
public MetaTagHandler(TagConfig config) {
super(config);
}
/**
* Extend this method in order to add your own rules.
*
* @param type
*/
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
* @param 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);
}
}
}