FrameworkPropertyAccessor.java

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2012-2013 ForgeRock AS. All Rights Reserved
 *
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the License). You may not use this file except in
 * compliance with the License.
 *
 * You can obtain a copy of the License at
 * http://forgerock.org/license/CDDLv1.0.html
 * See the License for the specific language governing
 * permission and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * Header Notice in each file and include the License file
 * at http://forgerock.org/license/CDDLv1.0.html
 * If applicable, add the following below the CDDL Header,
 * with the fields enclosed by brackets [] replaced by
 * your own identifying information:
 * "Portions Copyrighted [year] [name of copyright owner]"
 */

package org.forgerock.openidm.core;

import org.osgi.framework.BundleContext;

/**
 * A FrameworkPropertyAccessor wraps the {@link BundleContext} and accesses all
 * Framework properties.
 *
 */
public class FrameworkPropertyAccessor implements PropertyAccessor {

    private final PropertyAccessor delegate;
    private final BundleContext context;

    public FrameworkPropertyAccessor(BundleContext context, PropertyAccessor delegate) {
        assert null != context;
        this.delegate = delegate;
        this.context = context;
    }

    /**
     * Returns the value of the specified property. If the key is not found in
     * the Framework properties, the system properties are then searched and
     * {@code delegate} is then requested. The method returns {@code null} if
     * the property is not found.
     *
     * @param key
     *            The name of the requested property.
     * @param defaultValue
     *            The value to return if the property is not found.
     * @param expected
     *            The type of the expected value.
     * @param <T>
     *            The type of the expected property.
     * @return The value of the requested property, or {@code null} if the
     *         property is undefined.
     * @throws SecurityException
     *             If the caller does not have the appropriate
     *             {@code PropertyPermission} to read the property, and the Java
     *             Runtime Environment supports permissions.
     */
    @SuppressWarnings("unchecked")
    public <T> T getProperty(String key, T defaultValue, Class<T> expected) {
        T value = null;
        if (null != key
                && ((null != expected && expected.isAssignableFrom(String.class)) || defaultValue instanceof String)) {
            value = (T) context.getProperty(key);
            if (value == null) {
                value = defaultValue;
            }
        }
        return null != value ? value : (null != delegate) ? delegate.getProperty(key, defaultValue,
                expected) : null;
    }
}