Jetty example source code file (Scanner.java)

This example Jetty source code file (Scanner.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Jetty tags/keywords

error, exception, exception, file, file, io, iterator, iterator, list, listener, map, string, string, timer, timertask, util

The Jetty Scanner.java source code

//========================================================================
//$Id: Scanner.java 2388 2008-02-28 04:01:45Z gregw $
//Copyright 2006 Mort Bay Consulting Pty. Ltd.
//------------------------------------------------------------------------
//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.mortbay.util;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Timer;
import java.util.TimerTask;

import org.mortbay.log.Log;


/**
 * Scanner
 * 
 * Utility for scanning a directory for added, removed and changed
 * files and reporting these events via registered Listeners.
 *
 * TODO AbstractLifeCycle
 */
public class Scanner
{
    private int _scanInterval;
    private List _listeners = Collections.synchronizedList(new ArrayList());
    private Map _prevScan = Collections.EMPTY_MAP;
    private FilenameFilter _filter;
    private List _scanDirs;
    private volatile boolean _running = false;
    private boolean _reportExisting = true;
    private Timer _timer;
    private TimerTask _task;
    private boolean _recursive=true;

    /**
     * Listener
     * 
     * Marker for notifications re file changes.
     */
    public interface Listener
    {
    }

    
    public interface DiscreteListener extends Listener
    {
        public void fileChanged (String filename) throws Exception;
        public void fileAdded (String filename) throws Exception;
        public void fileRemoved (String filename) throws Exception;
    }
    
    
    public interface BulkListener extends Listener
    {
        public void filesChanged (List filenames) throws Exception;
    }


    /**
     * 
     */
    public Scanner ()
    {       
    }

    /**
     * Get the scan interval
     * @return interval between scans in seconds
     */
    public int getScanInterval()
    {
        return _scanInterval;
    }

    /**
     * Set the scan interval
     * @param scanInterval pause between scans in seconds
     */
    public synchronized void setScanInterval(int scanInterval)
    {
        this._scanInterval = scanInterval;
        
        if (_running)
        {
            stop();

            _timer = newTimer();
            _task = newTimerTask();

            schedule(_timer, _task);
            _running = true;
        }
    }

    /**
     * Set the location of the directory to scan.
     * @param dir
     * @deprecated use setScanDirs(List dirs) instead
     */
    public void setScanDir (File dir)
    {
        _scanDirs = new ArrayList();
        _scanDirs.add(dir);
    }

    /**
     * Get the location of the directory to scan
     * @return
     * @deprecated use getScanDirs() instead
     */
    public File getScanDir ()
    {
        return (_scanDirs==null?null:(File)_scanDirs.get(0));
    }

    public void setScanDirs (List dirs)
    {
        _scanDirs = dirs;
    }
    
    public List getScanDirs ()
    {
        return _scanDirs;
    }
    
    public void setRecursive (boolean recursive)
    {
        _recursive=recursive;
    }
    
    public boolean getRecursive ()
    {
        return _recursive;
    }
    /**
     * Apply a filter to files found in the scan directory.
     * Only files matching the filter will be reported as added/changed/removed.
     * @param filter
     */
    public void setFilenameFilter (FilenameFilter filter)
    {
        this._filter = filter;
    }

    /**
     * Get any filter applied to files in the scan dir.
     * @return
     */
    public FilenameFilter getFilenameFilter ()
    {
        return _filter;
    }

    /**
     * Whether or not an initial scan will report all files as being
     * added.
     * @param reportExisting if true, all files found on initial scan will be 
     * reported as being added, otherwise not
     */
    public void setReportExistingFilesOnStartup (boolean reportExisting)
    {
        this._reportExisting = reportExisting;
    }

    /**
     * Add an added/removed/changed listener
     * @param listener
     */
    public synchronized void addListener (Listener listener)
    {
        if (listener == null)
            return;

        _listeners.add(listener);   
    }



    /**
     * Remove a registered listener
     * @param listener the Listener to be removed
     */
    public synchronized void removeListener (Listener listener)
    {
        if (listener == null)
            return;
        _listeners.remove(listener);    
    }


    /**
     * Start the scanning action.
     */
    public synchronized void start ()
    {
        if (_running)
            return;

        _running = true;

        if (_reportExisting)
        {
            // if files exist at startup, report them
            scan();
        }
        else
        {
            //just register the list of existing files and only report changes
            _prevScan = scanFiles();
        }

        _timer = newTimer();
        _task = newTimerTask();

        schedule(_timer, _task);
        
    }

    public TimerTask newTimerTask ()
    {
        return new TimerTask()
        {
            public void run() { scan(); }
        };
    }

    public Timer newTimer ()
    {
        return new Timer(true);
    }
    
    public void schedule (Timer timer, TimerTask task)
    {
        if (timer==null)
            throw new IllegalArgumentException("Timer is null");
        if (task==null)
            throw new IllegalArgumentException("TimerTask is null");
        
        if (getScanInterval() > 0)
            timer.schedule(task, 1000L*getScanInterval(),1000L*getScanInterval());
    }
    /**
     * Stop the scanning.
     */
    public synchronized void stop ()
    {
        if (_running)
        {
            _running = false; 
            _timer.cancel();
            _task.cancel();
            _task=null;
            _timer=null;
        }
    }

    /**
     * Perform a pass of the scanner and report changes
     */
    public void scan ()
    {
        Map currentScan = scanFiles();
        reportDifferences(currentScan, _prevScan);
        _prevScan = currentScan;     
    }

    /**
     * Recursively scan all files in the designated directories.
     * @return Map of name of file to last modified time
     */
    public Map scanFiles ()
    {
        if (_scanDirs==null)
            return Collections.EMPTY_MAP;
        
        HashMap scanInfo = new HashMap();
        Iterator itor = _scanDirs.iterator();
        while (itor.hasNext())
        {
            File dir = (File)itor.next();
            
            if ((dir != null) && (dir.exists()))
                scanFile(dir, scanInfo);
        }
        
        return scanInfo;
    }


    /**
     * Report the adds/changes/removes to the registered listeners
     * 
     * @param currentScan the info from the most recent pass
     * @param oldScan info from the previous pass
     */
    public void reportDifferences (Map currentScan, Map oldScan) 
    {
        List bulkChanges = new ArrayList();
        
        Set oldScanKeys = new HashSet(oldScan.keySet());
        Iterator itor = currentScan.entrySet().iterator();
        while (itor.hasNext())
        {
            Map.Entry entry = (Map.Entry)itor.next();
            if (!oldScanKeys.contains(entry.getKey()))
            {
                Log.debug("File added: "+entry.getKey());
                reportAddition ((String)entry.getKey());
                bulkChanges.add(entry.getKey());
            }
            else if (!oldScan.get(entry.getKey()).equals(entry.getValue()))
            {
                Log.debug("File changed: "+entry.getKey());
                reportChange((String)entry.getKey());
                oldScanKeys.remove(entry.getKey());
                bulkChanges.add(entry.getKey());
            }
            else
                oldScanKeys.remove(entry.getKey());
        }

        if (!oldScanKeys.isEmpty())
        {

            Iterator keyItor = oldScanKeys.iterator();
            while (keyItor.hasNext())
            {
                String filename = (String)keyItor.next();
                Log.debug("File removed: "+filename);
                reportRemoval(filename);
                bulkChanges.add(filename);
            }
        }
        
        if (!bulkChanges.isEmpty())
            reportBulkChanges(bulkChanges);
    }


    /**
     * Get last modified time on a single file or recurse if
     * the file is a directory. 
     * @param f file or directory
     * @param scanInfoMap map of filenames to last modified times
     */
    private void scanFile (File f, Map scanInfoMap)
    {
        try
        {
            if (!f.exists())
                return;

            if (f.isFile())
            {
                if ((_filter == null) || ((_filter != null) && _filter.accept(f.getParentFile(), f.getName())))
                {
                    String name = f.getCanonicalPath();
                    long lastModified = f.lastModified();
                    scanInfoMap.put(name, new Long(lastModified));
                }
            }
            else if (f.isDirectory() && (_recursive || _scanDirs.contains(f)))
            {
                File[] files = f.listFiles();
                for (int i=0;i<files.length;i++)
                    scanFile(files[i], scanInfoMap);
            }
        }
        catch (IOException e)
        {
            Log.warn("Error scanning watched files", e);
        }
    }

    private void warn(Object listener,String filename,Throwable th)
    {
        Log.warn(th);
        Log.warn(listener+" failed on '"+filename);
    }

    /**
     * Report a file addition to the registered FileAddedListeners
     * @param filename
     */
    private void reportAddition (String filename)
    {
        Iterator itor = _listeners.iterator();
        while (itor.hasNext())
        {
            Object l = itor.next();
            try
            {
                if (l instanceof DiscreteListener)
                    ((DiscreteListener)l).fileAdded(filename);
            }
            catch (Exception e)
            {
                warn(l,filename,e);
            }
            catch (Error e)
            {
                warn(l,filename,e);
            }
        }
    }


    /**
     * Report a file removal to the FileRemovedListeners
     * @param filename
     */
    private void reportRemoval (String filename)
    {
        Iterator itor = _listeners.iterator();
        while (itor.hasNext())
        {
            Object l = itor.next();
            try
            {
                if (l instanceof DiscreteListener)
                    ((DiscreteListener)l).fileRemoved(filename);
            }
            catch (Exception e)
            {
                warn(l,filename,e);
            }
            catch (Error e)
            {
                warn(l,filename,e);
            }
        }
    }


    /**
     * Report a file change to the FileChangedListeners
     * @param filename
     */
    private void reportChange (String filename)
    {
        Iterator itor = _listeners.iterator();
        while (itor.hasNext())
        {
            Object l = itor.next();
            try
            {
                if (l instanceof DiscreteListener)
                    ((DiscreteListener)l).fileChanged(filename);
            }
            catch (Exception e)
            {
                warn(l,filename,e);
            }
            catch (Error e)
            {
                warn(l,filename,e);
            }
        }
    }
    
    private void reportBulkChanges (List filenames)
    {
        Iterator itor = _listeners.iterator();
        while (itor.hasNext())
        {
            Object l = itor.next();
            try
            {
                if (l instanceof BulkListener)
                    ((BulkListener)l).filesChanged(filenames);
            }
            catch (Exception e)
            {
                warn(l,filenames.toString(),e);
            }
            catch (Error e)
            {
                warn(l,filenames.toString(),e);
            }
        }
    }

}