NullElementHandler.java

/*
 * 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
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package com.sun.beans.decoder;

/**
 * This class is intended to handle <null> element.
 * This element specifies {@code null} value.
 * It should not contain body or inner elements.
 * For example:<pre>
 * &lt;null/&gt;</pre>
 * is equivalent to {@code null} in Java code.
 * <p>The following attribute is supported:
 * <dl>
 * <dt>id
 * <dd>the identifier of the variable that is intended to store the result
 * </dl>
 *
 * @since 1.7
 *
 * @author Sergey A. Malenkov
 */
class NullElementHandler extends ElementHandler implements ValueObject {

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

    /**
     * Returns {@code null}
     * as a value of &lt;null&gt; element.
     * This method should be overridden in those handlers
     * that extend behavior of this element.
     *
     * @return {@code null} by default
     */
    public Object getValue() {
        return null;
    }

    /**
     * Returns {@code void} state of this value object.
     *
     * @return {@code false} always
     */
    public final boolean isVoid() {
        return false;
    }
}