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JSR-000372: JavaServer(TM) Faces 2.3 API
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/*
 * Copyright (c) 1997, 2018 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 javax.faces.view.facelets;

/**
 * The root class of the abstraction that dictates
 * how attributes on a markup element in a Facelets VDL page are wired to the
 * Jakarta Server Faces API object instance associated with that element. The single method on
 * this interface, {@link #applyRule}, returns an encapsulation of the behavior
 * that actually does the work of handling the attribute and its value. There
 * are implementations of specific concrete subclasses of this class for all the
 * basic kinds of elements that appear in Facelets VDL pages: components,
 * non-components, and attached objects.
 *
 * 
 *
 * 
 * For example, consider this markup:
 *
<h:inputText value="#{user.userid}"
 * valueChangeListener="#{user.newUserId}" />
 *
 * 
 * Two MetaRule instances are involved in this example.
 *
 * 
 *
 * 
 * The first has an applyRule() method that returns a
 * {@link Metadata} instance that, when its applyMetada() method is
 * called, dictates how the "value" attribute is processed: calling {@link
 * javax.faces.component.UIComponent#setValueExpression} on the
 * UIComponent instance associated with the
 * <h:inputText> element.
 *
 * 
 * The second has an applyRule() method that returns a
 * {@link Metadata} instance that, when its applyMetadata() method
 * is called, dictates how the "valueChangeListener" attribute is processed:
 * calling {@link
 * javax.faces.component.EditableValueHolder#addValueChangeListener}.
 *
 * 
 *
 * 
 *
 * @since 2.0
 */
public abstract class MetaRule {

    /**
     * Return an abstraction that takes appropriate
     * action given the kind of rule represented by the argument
     * name, in the context of this particular concrete subclass of
     * MetaRule. The abstraction must encapsulate the value from
     * the argument attribute.
     *
     * @param name the name for this rule. This will generally be the name of a
     * tag attribute in the VDL.
     * @param attribute the name/value pair for this attribute on this
     * particular instance of an element in the page.
     * @param meta the MetadataTarged that can be used to discern
     * what kind of action to encapsulate within the abstraction to be returned.
     * @return the {@link Metadata}.
     * @since 2.0
     */
    public abstract Metadata applyRule(String name, TagAttribute attribute,
            MetadataTarget meta);
}