commons-vfs2/src/main/java/org/apache/commons/vfs2/provider/AbstractVfsContainer.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.vfs2.provider;

import java.util.ArrayList;
import java.util.Arrays;

import org.apache.commons.vfs2.FileSystemException;

/**
 * A {@link VfsComponent} that contains a set of sub-components.
 */
public abstract class AbstractVfsContainer extends AbstractVfsComponent {

    /**
     * The components contained by this component.
     */
    private final ArrayList<Object> components = new ArrayList<>(); // @GuardedBy("self")

    /**
     * Adds a sub-component to this component.
     * <p>
     * If the sub-component implements {@link VfsComponent}, it is initialized. All sub-components are closed when this
     * component is closed.
     * </p>
     *
     * @param component the component to add.
     * @throws FileSystemException if any error occurs.
     */
    protected void addComponent(final Object component) throws FileSystemException {
        synchronized (components) {
            if (!components.contains(component)) {
                // Initialize
                if (component instanceof VfsComponent) {
                    final VfsComponent vfsComponent = (VfsComponent) component;
                    vfsComponent.setLogger(getLogger());
                    vfsComponent.setContext(getContext());
                    vfsComponent.init();
                }

                // Keep track of component, to close it later
                components.add(component);
            }
        } // synchronized
    }

    /**
     * Removes a sub-component from this component.
     *
     * @param component the component to remove.
     */
    protected void removeComponent(final Object component) {
        synchronized (components) {
            // multiple instances should not happen
            components.remove(component);
        }
    }

    /**
     * Closes the sub-components of this component.
     */
    @Override
    public void close() {
        final Object[] toclose;
        synchronized (components) {
            toclose = components.toArray();
            components.clear();
        }

        // Close all components
        Arrays.stream(toclose).filter(component -> component instanceof VfsComponent)
                              .forEach(component -> ((VfsComponent) component).close());
    }
}