WatchService loop running twice unless stepping through in debug mode - watchservice

Question

I am really new to WatchService and I am having a very interesting bug. When I run my code in normal mode(Run) it will loop through the for(Watch event: key1.pollEvents()) loop twice and create two google calander events but if I step through it using debug mode it only adds one event. I grabbed almost all of the code from online in an attempt to learn about how WatchService works. I don't really know what I am doing here so any help would be great. Here is my code
/*
* Copyright (c) 2010 Google Inc.
*
* 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 com.google.api.services.samples.calendar.cmdline;
import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
import com.google.api.client.extensions.java6.auth.oauth2.FileCredentialStore;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.util.DateTime;
import com.google.api.client.util.Lists;
import com.google.api.services.calendar.CalendarScopes;
import com.google.api.services.calendar.model.Calendar;
import com.google.api.services.calendar.model.Event;
import com.google.api.services.calendar.model.Event.Reminders;
import com.google.api.services.calendar.model.EventDateTime;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Scanner;
import java.util.TimeZone;
/**
* #author Yaniv Inbar
*/
public class myCalendar {
/**
* Be sure to specify the name of your application. If the application name is {#code null} or
* blank, the application will log a warning. Suggested format is "MyCompany-ProductName/1.0".
*/
private static final String APPLICATION_NAME = "";
/** Global instance of the HTTP transport. */
private static HttpTransport HTTP_TRANSPORT;
/** Global instance of the JSON factory. */
private static final JsonFactory JSON_FACTORY = new JacksonFactory();
private static com.google.api.services.calendar.Calendar client;
static final java.util.List<Calendar> addedCalendarsUsingBatch = Lists.newArrayList();
/** Authorizes the installed application to access user's protected data. */
private static Credential authorize() throws Exception {
// load client secrets
GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY,
new InputStreamReader(myCalendar.class.getResourceAsStream("/client_secrets.json")));
if (clientSecrets.getDetails().getClientId().startsWith("Enter")
|| clientSecrets.getDetails().getClientSecret().startsWith("Enter ")) {
System.out.println(
"Enter Client ID and Secret from https://code.google.com/apis/console/?api=calendar "
+ "into calendar-cmdline-sample/src/main/resources/client_secrets.json");
System.exit(1);
}
// set up file credential store
FileCredentialStore credentialStore = new FileCredentialStore(
new File(System.getProperty("user.home"), ".credentials/calendar.json"), JSON_FACTORY);
// set up authorization code flow
GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
HTTP_TRANSPORT, JSON_FACTORY, clientSecrets,
Collections.singleton(CalendarScopes.CALENDAR)).setCredentialStore(credentialStore).build();
// authorize
return new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
}
public static void main(String[] args) throws IOException {
Path dir = Paths.get("C:\\Users\\kdevocht\\Dropbox\\Apps\\Attachments\\kjdevocht#gmail.com\\");
WatchService service = FileSystems.getDefault().newWatchService();
WatchKey key = dir.register(service, ENTRY_MODIFY);
System.out.println("Watching directory: "+dir.toString());
for(;;){
WatchKey key1;
try {
key1 = service.take();
} catch (InterruptedException x) {
break;
}
for (WatchEvent<?> event: key1.pollEvents()) {
WatchEvent.Kind<?> kind = event.kind();
if (kind == OVERFLOW) {
continue;
}
WatchEvent<Path> ev = (WatchEvent<Path>)event;
Path filename = ev.context();
Path child = dir.resolve(filename);
System.out.println("File: "+child.toString()+" modified.");
try{
try {
try {
// initialize the transport
HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
// authorization
Credential credential = authorize();
// set up global Calendar instance
client = new com.google.api.services.calendar.Calendar.Builder(
HTTP_TRANSPORT, JSON_FACTORY, credential).setApplicationName(
APPLICATION_NAME).build();
// run commands
Calendar calendar = client.calendars().get("kjdevocht#gmail.com").execute();
addEvent(calendar, child.toString());
} catch (IOException e) {
System.err.println(e.getMessage());
}
} catch (Throwable t) {
t.printStackTrace();
}
//System.exit(1);;
}catch(Exception x){
x.printStackTrace();
}
}
boolean valid = key.reset();
if (!valid) {
break;
}
/* try {
Thread.sleep(5000);
} catch(InterruptedException e) {
} */
}
I thought it might have been a timing issue so I tried a sleep try catch but that did not work.

Answer 1

So it seems everything was working fine. I was using notepad++ to edit a file in the dir I was watching. After some research it appears that two modifications are made and so two events are logged. Some people have suggested storing the time stamp of the file and only react when it changes, this seems to filter out the multiple events. For me and what I was doing, I just changed to watching for a create event. This works great now with no problems