src/java/org/apache/commons/vfs/provider/DelegateFileObject.java

/*
 * Copyright 2002-2005 The Apache Software Foundation.
 *
 * Licensed 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.vfs.provider;

import org.apache.commons.vfs.FileChangeEvent;
import org.apache.commons.vfs.FileListener;
import org.apache.commons.vfs.FileName;
import org.apache.commons.vfs.FileObject;
import org.apache.commons.vfs.FileSystemException;
import org.apache.commons.vfs.FileType;

import java.io.InputStream;
import java.io.OutputStream;
import java.security.cert.Certificate;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * A file backed by another file.
 *
 * @author <a href="mailto:adammurdoch@apache.org">Adam Murdoch</a>
 * @author Gary D. Gregory
 * @version $Revision$ $Date$
 * @todo Extract subclass that overlays the children
 */
public class DelegateFileObject
    extends AbstractFileObject
    implements FileListener
{
    private FileObject file;
    private final Set children = new HashSet();
    private boolean ignoreEvent;

    public DelegateFileObject(final FileName name,
                              final AbstractFileSystem fileSystem,
                              final FileObject file) throws FileSystemException
    {
        super(name, fileSystem);
        this.file = file;
        if (file != null)
        {
            file.getFileSystem().addListener(file, this);
        }
    }

    /**
     * Adds a child to this file.
     */
    public void attachChild(final String baseName) throws Exception
    {
        final FileType oldType = doGetType();
        if (children.add(baseName))
        {
            childrenChanged();
        }
        maybeTypeChanged(oldType);
    }

    /**
     * Attaches or detaches the target file.
     */
    public void setFile(final FileObject file) throws Exception
    {
        final FileType oldType = doGetType();

        if (file != null)
        {
            file.getFileSystem().addListener(file, this);
        }
        this.file = file;
        maybeTypeChanged(oldType);
    }

    /**
     * Checks whether the file's type has changed, and fires the appropriate
     * events.
     */
    private void maybeTypeChanged(final FileType oldType) throws Exception
    {
        final FileType newType = doGetType();
        if (oldType == FileType.IMAGINARY && newType != FileType.IMAGINARY)
        {
            handleCreate(newType);
        }
        else if (oldType != FileType.IMAGINARY && newType == FileType.IMAGINARY)
        {
            handleDelete();
        }
    }

    /**
     * Determines the type of the file, returns null if the file does not
     * exist.
     */
    protected FileType doGetType() throws FileSystemException
    {
        if (file != null)
        {
            return file.getType();
        }
        else if (children.size() > 0)
        {
            return FileType.FOLDER;
        }
        else
        {
            return FileType.IMAGINARY;
        }
    }

    /**
     * Determines if this file can be read.
     */
    protected boolean doIsReadable() throws FileSystemException
    {
        if (file != null)
        {
            return file.isReadable();
        }
        else
        {
            return true;
        }
    }

    /**
     * Determines if this file can be written to.
     */
    protected boolean doIsWriteable() throws FileSystemException
    {
        if (file != null)
        {
            return file.isWriteable();
        }
        else
        {
            return false;
        }
    }

    /**
     * Determines if this file is hidden.
     */
    protected boolean doIsHidden() throws FileSystemException
    {
        if (file != null)
        {
            return file.isHidden();
        }
        else
        {
            return false;
        }
    }

    /**
     * Lists the children of the file.
     */
    protected String[] doListChildren() throws Exception
    {
        if (file != null)
        {
            final FileObject[] children = file.getChildren();
            final String[] childNames = new String[children.length];
            for (int i = 0; i < children.length; i++)
            {
                childNames[i] = children[i].getName().getBaseName();
            }
            return childNames;
        }
        else
        {
            return (String[]) children.toArray(new String[children.size()]);
        }
    }

    /**
     * Creates this file as a folder.
     */
    protected void doCreateFolder() throws Exception
    {
        ignoreEvent = true;
        try
        {
            file.createFolder();
        }
        finally
        {
            ignoreEvent = false;
        }
    }

    /**
     * Deletes the file.
     */
    protected void doDelete() throws Exception
    {
        ignoreEvent = true;
        try
        {
            file.delete();
        }
        finally
        {
            ignoreEvent = false;
        }
    }

    /**
     * Returns the size of the file content (in bytes).  Is only called if
     * {@link #doGetType} returns {@link FileType#FILE}.
     */
    protected long doGetContentSize() throws Exception
    {
        return file.getContent().getSize();
    }

    /**
     * Returns the attributes of this file.
     */
    protected Map doGetAttributes()
        throws Exception
    {
        return file.getContent().getAttributes();
    }

    /**
     * Sets an attribute of this file.
     */
    protected void doSetAttribute(final String atttrName,
                                  final Object value)
        throws Exception
    {
        file.getContent().setAttribute(atttrName, value);
    }

    /**
     * Returns the certificates of this file.
     */
    protected Certificate[] doGetCertificates() throws Exception
    {
        return file.getContent().getCertificates();
    }

    /**
     * Returns the last-modified time of this file.
     */
    protected long doGetLastModifiedTime() throws Exception
    {
        return file.getContent().getLastModifiedTime();
    }

    /**
     * Sets the last-modified time of this file.
     */
    protected void doSetLastModifiedTime(final long modtime)
        throws Exception
    {
        file.getContent().setLastModifiedTime(modtime);
    }

    /**
     * Creates an input stream to read the file content from.
     */
    protected InputStream doGetInputStream() throws Exception
    {
        return file.getContent().getInputStream();
    }

    /**
     * Creates an output stream to write the file content to.
     */
    protected OutputStream doGetOutputStream(boolean bAppend) throws Exception
    {
        return file.getContent().getOutputStream(bAppend);
    }

    /**
     * Called when a file is created.
     */
    public void fileCreated(final FileChangeEvent event) throws Exception
    {
        if (!ignoreEvent)
        {
            handleCreate(file.getType());
        }
    }

    /**
     * Called when a file is deleted.
     */
    public void fileDeleted(final FileChangeEvent event) throws Exception
    {
        if (!ignoreEvent)
        {
            handleDelete();
        }
    }

    /**
     * Called when a file is changed.
     * <p/>
     * This will only happen if you monitor the file using {@link org.apache.commons.vfs.FileMonitor}.
     */
    public void fileChanged(FileChangeEvent event) throws Exception
    {
        if (!ignoreEvent)
        {
            handleChanged();
        }
    }

    /**
     * Close the delegated file
     */
    public void close() throws FileSystemException
    {
        super.close();

        if (file != null)
        {
            file.close();
        }
    }
}