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	/*
	* Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package com.sun.beans.decoder;

	/**
	* The base class for element handlers.
	*
	* @since 1.7
	*
	* @author Sergey A. Malenkov
	*
	* @see DocumentHandler
	*/
	public abstract class ElementHandler {
	private DocumentHandler owner;
	private ElementHandler parent;

	private String id;

	/**
	* Returns the document handler that creates this element handler.
	*
	* @return the owner document handler
	*/
	public final DocumentHandler getOwner() {
	return this.owner;
	}

	/**
	* Sets the document handler that creates this element handler.
	* The owner document handler should be set after instantiation.
	* Such approach is used to simplify the extensibility.
	*
	* @param owner the owner document handler
	* @see DocumentHandler#startElement
	*/
	final void setOwner(DocumentHandler owner) {
	if (owner == null) {
	throw new IllegalArgumentException("Every element should have owner");
	}
	this.owner = owner;
	}

	/**
	* Returns the element handler that contains this one.
	*
	* @return the parent element handler
	*/
	public final ElementHandler getParent() {
	return this.parent;
	}

	/**
	* Sets the element handler that contains this one.
	* The parent element handler should be set after instantiation.
	* Such approach is used to simplify the extensibility.
	*
	* @param parent the parent element handler
	* @see DocumentHandler#startElement
	*/
	final void setParent(ElementHandler parent) {
	this.parent = parent;
	}

	/**
	* Returns the value of the variable with specified identifier.
	*
	* @param id the identifier
	* @return the value of the variable
	*/
	protected final Object getVariable(String id) {
	if (id.equals(this.id)) {
	ValueObject value = getValueObject();
	if (value.isVoid()) {
	throw new IllegalStateException("The element does not return value");
	}
	return value.getValue();
	}
	return (this.parent != null)
	? this.parent.getVariable(id)
	: this.owner.getVariable(id);
	}

	/**
	* Returns the value of the parent element.
	*
	* @return the value of the parent element
	*/
	protected Object getContextBean() {
	if (this.parent != null) {
	ValueObject value = this.parent.getValueObject();
	if (!value.isVoid()) {
	return value.getValue();
	}
	throw new IllegalStateException("The outer element does not return value");
	} else {
	Object value = this.owner.getOwner();
	if (value != null) {
	return value;
	}
	throw new IllegalStateException("The topmost element does not have context");
	}
	}

	/**
	* Parses attributes of the element.
	* By default, the following attribute is supported:
	* <dl>
	* <dt>id
	* <dd>the identifier of the variable that is intended to store the result
	* </dl>
	*
	* @param name the attribute name
	* @param value the attribute value
	*/
	public void addAttribute(String name, String value) {
	if (name.equals("id")) { // NON-NLS: the attribute name
	this.id = value;
	} else {
	throw new IllegalArgumentException("Unsupported attribute: " + name);
	}
	}

	/**
	* This method is called before parsing of the element's body.
	* All attributes are parsed at this point.
	* By default, do nothing.
	*/
	public void startElement() {
	}

	/**
	* This method is called after parsing of the element's body.
	* By default, it calculates the value of this element.
	* The following tasks are executing for any non-void value:
	* <ol>
	* <li>If the {@code id} attribute is set
	* the value of the variable with the specified identifier
	* is set to the value of this element.</li>
	* <li>This element is used as an argument of parent element if it is possible.</li>
	* </ol>
	*
	* @see #isArgument
	*/
	public void endElement() {
	// do nothing if no value returned
	ValueObject value = getValueObject();
	if (!value.isVoid()) {
	if (this.id != null) {
	this.owner.setVariable(this.id, value.getValue());
	}
	if (isArgument()) {
	if (this.parent != null) {
	this.parent.addArgument(value.getValue());
	} else {
	this.owner.addObject(value.getValue());
	}
	}
	}
	}

	/**
	* Adds the character that contained in this element.
	* By default, only whitespaces are acceptable.
	*
	* @param ch the character
	*/
	public void addCharacter(char ch) {
	if ((ch != ' ') && (ch != '\n') && (ch != '\t') && (ch != '\r')) {
	throw new IllegalStateException("Illegal character with code " + (int) ch);
	}
	}

	/**
	* Adds the argument that is used to calculate the value of this element.
	* By default, no arguments are acceptable.
	*
	* @param argument the value of the element that contained in this one
	*/
	protected void addArgument(Object argument) {
	throw new IllegalStateException("Could not add argument to simple element");
	}

	/**
	* Tests whether the value of this element can be used
	* as an argument of the element that contained in this one.
	*
	* @return {@code true} if the value of this element can be used
	* as an argument of the element that contained in this one,
	* {@code false} otherwise
	*/
	protected boolean isArgument() {
	return this.id == null;
	}

	/**
	* Returns the value of this element.
	*
	* @return the value of this element
	*/
	protected abstract ValueObject getValueObject();
	}

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