[jira] Commented: (VFS-299) Listeners on DefaultFileMonitor not deregistered on stop()

["Josua Troesch (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/VFS-299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12832610#action_12832610 ] 

Josua Troesch commented on VFS-299:
-----------------------------------

_Here some example Code to clarify:_

import org.apache.commons.io.FileUtils;
import org.apache.commons.vfs.FileChangeEvent;
import org.apache.commons.vfs.FileListener;
import org.apache.commons.vfs.FileObject;
import org.apache.commons.vfs.VFS;
import org.apache.commons.vfs.impl.DefaultFileMonitor;

import java.io.File;
import java.io.IOException;

public class MinimalFileMonitorBug {
    private static final String path = "dummy.txt";

    public static void main(String[] args) throws IOException, InterruptedException {
        MyFileListener listener1 = new MyFileListener();
        DefaultFileMonitor fileMonitor = new DefaultFileMonitor(listener1);
        fileMonitor.addFile(getFileObject());
        fileMonitor.start();
        // Normal operation ...
        fileMonitor.stop();
        // Deliberately writing on file without getting notified.
        MyFileListener listener2 = new MyFileListener();
        fileMonitor = new DefaultFileMonitor(listener2);
        fileMonitor.addFile(getFileObject());
        fileMonitor.start();
        Thread.sleep(1500);
        FileUtils.writeStringToFile(getFile(), "new content");
        Thread.sleep(1500);
    }

    private static FileObject getFileObject() throws IOException {
        return VFS.getManager().resolveFile(getFile().getAbsolutePath());
    }

    private static File getFile() throws IOException {
        File file = new File(path);
        if (!file.exists()) {
            file.createNewFile();
        }
        return file;
    }

    static class MyFileListener implements FileListener {
        @Override
        public void fileCreated(FileChangeEvent fileChangeEvent) throws Exception {
        }

        @Override
        public void fileDeleted(FileChangeEvent fileChangeEvent) throws Exception {
        }

        @Override
        public void fileChanged(FileChangeEvent fileChangeEvent) throws Exception {
            System.out.println(String.format("File [%s] changed event from [%s]", fileChangeEvent.getFile().getName(), this));
        }
    }
}

*Output:*

File [file:///E:/test/dummy.txt] changed event from [MinimalFileMonitorBug$MyFileListener@14b7453]
File [file:///E:/test/dummy.txt] changed event from [MinimalFileMonitorBug$MyFileListener@c21495]

> Listeners on DefaultFileMonitor not deregistered on stop()
> ----------------------------------------------------------
>
>                 Key: VFS-299
>                 URL: https://issues.apache.org/jira/browse/VFS-299
>             Project: Commons VFS
>          Issue Type: Bug
>    Affects Versions: 1.0
>         Environment: windows xp
>            Reporter: Josua Troesch
>            Priority: Minor
>
> If I 
> 1. register a File to a DefaultFileMonitor
> 2. stop() that DefaultFileMonitor
> 3. create a new DefaultFileMonitor and
> 4. register the same File to it
> 5. write to the File
> I get the {{FileChangeEvent}} on both listeners, on the one registered to the new DefaultFileMonitor (as expected) but also on the one registered to the stopped DefaultFileMonitor. I tracked it down to the {{LocalFileSystem.listenerMap}} containing both listeners for the File. In my project I fixed this behaviour as follows:
> Extended the {{stop()}} method on {{DefaultFileMonitor}}:
> public void stop() {
>     this.shouldRun = false;
> 	// Inserted this bit
> 	for (FileMonitorAgent agent : (Collection<FileMonitorAgent>)monitorMap.values()) {
> 		agent.removeListeners();
> 	}
> }
> And adding the method to the {{DefaultFileMonitor$FileMonitorAgent}}:
> public void removeListeners() {
> 	file.getFileSystem().removeListener(file, fm.getFileListener());
> }

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