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/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
* Copyright 2005-2007 The Apache Software Foundation
*
* Licensed 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.
*/
package jakarta.faces.view.facelets;
/**
*
* Every kind of markup element in Facelets VDL that has attributes that need to take action on a Jakarta Faces
* 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 Jakarta Faces Java
* API. For example, consider this markup:
*
*
*
*
*
* <h:inputText value="#{user.userid}"
* valueChangeListener="#{user.newUserId}" />
*
*
*
* This markup element corresponds to an instance of {@link jakarta.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 jakarta.faces.component.EditableValueHolder}, which extends
* {@link jakarta.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 Jakarta Faces 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 || !lastType.equals(type)) {
lastType = type;
mapper = createMetaRuleset(type).finish();
}
mapper.applyMetadata(ctx, instance);
}
}
}