ViewIterator.java

/*
 * Copyright 2004 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 org.apache.myfaces.util;

import javax.faces.component.UIComponent;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Stack;

/**
 * Iterates over a view structure, i.e. a component tree, in a
 * depth first manner.
 *
 * @author Manfred Geiler (latest modification by $Author$)
 * @version $Revision$ $Date$
 */
public class ViewIterator
        implements Iterator
{
    //private static final Log log = LogFactory.getLog(ViewIterator.class);
    private UIComponent _next = null;
    private boolean _mayHaveNext = true;
    private UIComponent _current = null;
    private Stack _stack = new Stack();

    /**
     * @param root the root of the view structure to iterate over
     */
    public ViewIterator(UIComponent root)
    {
        _next = root;
        _current = null;
    }

    public boolean hasNext()
    {
        return getNext() != null;
    }

    /**
     * @return the next component in the view. The first element is always the given root
     * component.
     */
    public Object next()
    {
        if (!hasNext())
        {
            throw new NoSuchElementException();
        }
        _current = _next;
        _next = null;
        return _current;
    }

    private UIComponent getNext()
    {
        if (_next == null && _mayHaveNext)
        {
            //has child?
            Iterator children = _current.getFacetsAndChildren();
            if (children.hasNext())
            {
                _next = (UIComponent)children.next();
                //push siblings
                _stack.push(children);
            }
            else
            {
                //has next sibling?
                for (;;)
                {
                    if (_stack.empty())
                    {
                        _next = null;
                        _mayHaveNext = false;
                        break;
                    }

                    Iterator currentSiblings = (Iterator)_stack.peek();
                    if (currentSiblings.hasNext())
                    {
                        _next = (UIComponent)currentSiblings.next();
                        break;
                    }
                    else
                    {
                        _stack.pop();
                    }
                }
            }
        }
        return _next;
    }

    public void remove()
    {
        throw new UnsupportedOperationException(this.getClass().getName() + " UnsupportedOperationException");
    }
}