org.apache.wicket.markup.renderStrategy.DeepChildFirstVisitor.java Source code

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Here is the source code for org.apache.wicket.markup.renderStrategy.DeepChildFirstVisitor.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.wicket.markup.renderStrategy;

import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.visit.IVisit;
import org.apache.wicket.util.visit.IVisitor;
import org.apache.wicket.util.visit.Visit;

/**
 * 
 * @author Juergen Donnerstag
 */
// TODO Wicket 1.6 :
// - move to o.a.w.util.visit because this is a useful visitor impl
// - relax its generics, it could be: DeepChildFirstVisitor<R> implements IVisitor<Component, R>
public abstract class DeepChildFirstVisitor implements IVisitor<Component, Void> {
    /**
     * Construct.
     */
    public DeepChildFirstVisitor() {
    }

    /**
     * Render the child hierarchy headers.
     * 
     * @param rootComponent
     * @return The object return by component()
     */
    public final Visit<Void> visit(final Component rootComponent) {
        Visit<Void> visitor = new Visit<Void>();
        return visit(rootComponent, visitor);
    }

    /**
     * Render the child hierarchy headers.
     * 
     * @param rootComponent
     * @param visit
     * @return The object return by component()
     */
    public final Visit<Void> visit(final Component rootComponent, final Visit<Void> visit) {
        Args.notNull(rootComponent, "rootComponent");
        Args.notNull(visit, "visit");

        // Component's don't have children; only MarkupContainers do
        if (!(rootComponent instanceof MarkupContainer)) {
            // Call the visitor's callback method
            component(rootComponent, visit);
            return visit;
        }

        // while walking down, towards the deep child, we validate if the component is visible. If
        // not, there is no need to go any deeper
        if (preCheck(rootComponent) == false) {
            return visit;
        }

        if (visit.isContinue()) {
            // Iterate over all children
            for (Component child : (MarkupContainer) rootComponent) {
                // visit the child
                visit(child, visit);
                if (visit.isStopped()) {
                    return visit;
                }
            }
        }

        // visit "this"
        component(rootComponent, visit);
        return visit;
    }

    @Override
    public abstract void component(Component component, IVisit<Void> visit);

    /**
     * In order to find the deepest component, we traverse downwards starting from the root (e.g.
     * Page). However, once a component is not disabled (preCheck() returns false), iteration will
     * stop and traversal continues with the sibling.
     * 
     * @param component
     *            The component to be tested
     * @return True, if component is enabled
     */
    public abstract boolean preCheck(Component component);
}