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Adapted (moved from java.beans to ajava.beans) OpenJDK8 javabeans for Android. It's used by A-Jetty (Jetty 9.2 adapted for Android.)
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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;

/**
 * This is base class that simplifies access to entities (fields or properties).
 * The {@code name} attribute specifies the name of the accessible entity.
 * The element defines getter if it contains no argument
 * or setter if it contains one argument.
 *
 * @since 1.7
 *
 * @author Sergey A. Malenkov
 */
abstract class AccessorElementHandler extends ElementHandler {
    private String name;
    private ValueObject value;

    /**
     * Parses attributes of the element.
     * The following attributes are supported:
     * 
     * name
     * 
the name of the accessible entity
     * 
id
     * 
the identifier of the variable that is intended to store the result
     * 
     *
     * @param name   the attribute name
     * @param value  the attribute value
     */
    @Override
    public void addAttribute(String name, String value) {
        if (name.equals("name")) { // NON-NLS: the attribute name
            this.name = value;
        } else {
            super.addAttribute(name, value);
        }
    }

    /**
     * Adds the argument that is used to set the value of this element.
     *
     * @param argument  the value of the element that contained in this one
     */
    @Override
    protected final void addArgument(Object argument) {
        if (this.value != null) {
            throw new IllegalStateException("Could not add argument to evaluated element");
        }
        setValue(this.name, argument);
        this.value = ValueObjectImpl.VOID;
    }

    /**
     * Returns the value of this element.
     *
     * @return the value of this element
     */
    @Override
    protected final ValueObject getValueObject() {
        if (this.value == null) {
            this.value = ValueObjectImpl.create(getValue(this.name));
        }
        return this.value;
    }

    /**
     * Returns the value of the entity with specified {@code name}.
     *
     * @param name  the name of the accessible entity
     * @return the value of the specified entity
     */
    protected abstract Object getValue(String name);

    /**
     * Sets the new value for the entity with specified {@code name}.
     *
     * @param name   the name of the accessible entity
     * @param value  the new value for the specified entity
     */
    protected abstract void setValue(String name, Object value);
}