org.apache.taverna.plugin.impl.PluginDirectoryWatcher.java Source code

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Here is the source code for org.apache.taverna.plugin.impl.PluginDirectoryWatcher.java

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/**
 * 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.taverna.plugin.impl;

import java.io.File;

import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.log4j.Logger;
import org.apache.taverna.plugin.Plugin;
import org.apache.taverna.plugin.PluginException;

/**
 * Watches a plugin directory and adds or removes plugins when plugin files are added or removed
 * from the directory.
 * 
 * @author David Withers
 */
public class PluginDirectoryWatcher extends FileAlterationListenerAdaptor {

    private static final Logger logger = Logger.getLogger(PluginDirectoryWatcher.class);

    private final PluginManagerImpl pluginManager;
    private final File directory;

    private FileAlterationMonitor monitor;

    public PluginDirectoryWatcher(PluginManagerImpl pluginManager, File directory) {
        this.pluginManager = pluginManager;
        this.directory = directory;
        FileAlterationObserver observer = new FileAlterationObserver(directory);
        observer.addListener(this);
        monitor = new FileAlterationMonitor();
        monitor.addObserver(observer);
    }

    /**
     * Starts watching the plugin directory.
     * 
     * @throws PluginException
     */
    public void start() throws PluginException {
        try {
            monitor.start();
        } catch (Exception e) {
            throw new PluginException(String.format("Error starting watch on %1$s.", directory.getAbsolutePath()),
                    e);
        }
    }

    /**
     * Stops watching the plugin directory.
     * 
     * @throws PluginException
     */
    public void stop() throws PluginException {
        try {
            monitor.stop();
        } catch (Exception e) {
            throw new PluginException(String.format("Error stopping watch on %1$s.", directory.getAbsolutePath()),
                    e);
        }
    }

    @Override
    public void onFileCreate(File file) {
        try {
            Plugin plugin = pluginManager.installPlugin(file.toPath());
            plugin.start();
        } catch (PluginException e) {
            logger.warn("Error loading plugin file " + file, e);
        }
    }

    @Override
    public void onFileChange(File file) {
        onFileDelete(file);
        onFileCreate(file);
    }

    @Override
    public void onFileDelete(File file) {
        pluginManager.uninstallPlugin(file);
    }

}