org.ambud.marauder.source.readers.MarauderPollingTextFileReader.java Source code

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Here is the source code for org.ambud.marauder.source.readers.MarauderPollingTextFileReader.java

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/**
 * Copyright 2013 Ambud Sharma
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.2
 */
package org.ambud.marauder.source.readers;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.text.ParseException;

import org.apache.commons.vfs.FileChangeEvent;
import org.apache.commons.vfs.FileListener;
import org.apache.commons.vfs.FileObject;
import org.apache.commons.vfs.FileSystemException;
import org.apache.commons.vfs.FileSystemManager;
import org.apache.commons.vfs.VFS;
import org.apache.commons.vfs.impl.DefaultFileMonitor;

/**
 * Polls text file using Apache Commons VFS API and uses fires read events 
 * when changes are made to the file.
 * 
 * Such reader can be concrete implemented for DSV or other types of
 * text files and have pre-existing content. If a file doesn't exist a reader
 * can't be deployed to read it. 
 * 
 * @author Ambud Sharma
 *
 */
public abstract class MarauderPollingTextFileReader extends MarauderSimpleTextFileReader {

    private DefaultFileMonitor monitor = null;

    public MarauderPollingTextFileReader(File file, int pollingInterval)
            throws FileNotFoundException, FileSystemException {
        super(file);
        FileSystemManager fsMgr = VFS.getManager();
        FileObject fo = fsMgr.resolveFile(getFile().getAbsolutePath());
        this.monitor = new DefaultFileMonitor(new FileListener() {

            @Override
            public void fileDeleted(FileChangeEvent arg0) throws Exception {
                // can't do anything since the file is closed
                closeReader();
            }

            @Override
            public void fileCreated(FileChangeEvent arg0) throws Exception {
                // shouldn't happen if file already exist
            }

            @Override
            public void fileChanged(FileChangeEvent arg0) throws Exception {
                readFile();
            }
        });
        monitor.addFile(fo);
        monitor.setRecursive(false);
        monitor.setDelay(pollingInterval);
    }

    @Override
    public synchronized void readFile() throws IOException {
        String temp = null;
        while ((temp = getReader().readLine()) != null) {
            try {
                processReadLine(temp, getCounter());
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            incrementCounter();
        }
    }

}