src/main/java/org/apache/commons/configuration2/builder/CopyObjectDefaultHandler.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.commons.configuration2.builder;

import org.apache.commons.configuration2.beanutils.BeanHelper;
import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;

/**
 * <p>
 * A specialized implementation of {@code DefaultParametersHandler} that copies the properties of a
 * {@link BuilderParameters} object (passed at construction time) onto the object to be initialized.
 * </p>
 * <p>
 * Using this handler implementation makes specifying default values pretty straight-forward: Just create a
 * corresponding parameters object, initialize it as desired, and pass it to this class. When invoked the handler uses
 * functionality from <em>Commons BeanUtils</em> to copy all properties defined in the associated parameters object onto
 * the target object. This is based on reflection. Properties not available for the target object are silently ignored.
 * If an exception occurs during the copy operation, it is re-thrown as a runtime exception.
 * </p>
 * <p>
 * Note that there is no default way to create a defensive copy of the passed in parameters object; therefore, the
 * reference is stored. This makes it possible to change the parameters object later on, and the changes will be
 * effective when initializing objects afterwards. Client code should not rely on this feature.
 * </p>
 *
 * @since 2.0
 */
public class CopyObjectDefaultHandler implements DefaultParametersHandler<Object> {
    /** The source object with the properties to be initialized. */
    private final BuilderParameters source;

    /**
     * Creates a new instance of {@code CopyObjectDefaultHandler} and initializes it with the specified source object. The
     * properties defined by the source object are copied onto the objects to be initialized.
     *
     * @param src the source object (must not be <b>null</b>)
     * @throws IllegalArgumentException if the source object is <b>null</b>
     */
    public CopyObjectDefaultHandler(final BuilderParameters src) {
        if (src == null) {
            throw new IllegalArgumentException("Source object must not be null!");
        }
        source = src;
    }

    /**
     * Gets the source object of this handler. This is the object whose properties are copied on the objects to be
     * initialized.
     *
     * @return the source object of this {@code CopyObjectDefaultHandler}
     */
    public BuilderParameters getSource() {
        return source;
    }

    /**
     * {@inheritDoc} This implementation uses {@code PropertyUtils.copyProperties()} to copy all defined properties from the
     * source object onto the passed in parameters object. Both the map with properties (obtained via the
     * {@code getParameters()} method of the source parameters object) and other properties of the source object are copied.
     *
     * @throws ConfigurationRuntimeException if an exception occurs
     * @see BuilderParameters#getParameters()
     */
    @Override
    public void initializeDefaults(final Object parameters) {
        try {
            BeanHelper.copyProperties(parameters, getSource().getParameters());
            BeanHelper.copyProperties(parameters, getSource());
        } catch (final Exception e) {
            // Handle all reflection-related exceptions the same way
            throw new ConfigurationRuntimeException(e);
        }
    }
}