Develop Reference

WebListener prevents the web application to launch

I have a Vaadin web application, that is deploying OK.
BUT when I add a FolderWatcher service as a Listener using
#WebListener
The application fails to deploy, but it starts the thread if I disable the annotation #WebListener the application does deploy.
Folder watcher class
public class FolderWatchService {
private final WatchService watcher;
private final Map<WatchKey, Path> keys;
private static final Logger LOGGER = Logger.getLogger( FolderWatchService.class.getName() );
/**
* Creates a WatchService and registers the given directory
*/
public FolderWatchService(Path dir) throws IOException {
this.watcher = FileSystems.getDefault().newWatchService();
this.keys = new HashMap<WatchKey, Path>();
walkAndRegisterDirectories(dir);
}
/**
* Register the given directory with the WatchService; This function will be called by FileVisitor
*/
private void registerDirectory(Path dir) throws IOException
{
WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
keys.put(key, dir);
}
/**
* Register the given directory, and all its sub-directories, with the WatchService.
*/
private void walkAndRegisterDirectories(final Path start) throws IOException {
// register directory and sub-directories
Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
#Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
registerDirectory(dir);
return FileVisitResult.CONTINUE;
}
});
}
/**
* Process all events for keys queued to the watcher
*/
public void processEvents() {
for (;;) {
// wait for key to be signaled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return;
}
Path dir = keys.get(key);
if (dir == null) {
LOGGER.log( Level.FINE, "WatchKey not recognized!!", "" );
System.err.println("WatchKey not recognized!!");
continue;
}
for (WatchEvent<?> event : key.pollEvents()) {
#SuppressWarnings("rawtypes")
WatchEvent.Kind kind = event.kind();
// Context for directory entry event is the file name of entry
#SuppressWarnings("unchecked")
Path name = ((WatchEvent<Path>)event).context();
Path child = dir.resolve(name);
String fileContent;
// if directory is created, and watching recursively, then register it and its sub-directories
if (kind == ENTRY_CREATE) {
System.out.println("File created");
LOGGER.log( Level.FINER, "New File created", "" );
readFile(child.toString());
}
}
// reset key and remove from set if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
keys.remove(key);
// all directories are inaccessible
if (keys.isEmpty()) {
break;
}
}
}
}
private static void readFile(String pathname){
try {
File file = new File(pathname);
StringBuilder fileContents = new StringBuilder((int)file.length());
Scanner scanner = new Scanner(file);
String lineSeparator = System.getProperty("line.separator");
try {
while(scanner.hasNextLine()) {
fileContents.append(scanner.nextLine() + lineSeparator);
}
String fileContent = fileContents.toString();
System.out.println("File name: "+FilenameUtils.getBaseName(pathname));
LOGGER.log( Level.FINER, "File name: "+FilenameUtils.getBaseName(pathname), "" );
String title = "File Title: "+fileContent.substring(0, 64).trim().lastIndexOf(System.getProperty("line.separator"))+"...";
} finally {
scanner.close();
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
ContextLister class
#WebListener
public class ContextListener implements ServletContextListener {
#Override
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("#### Folder watcher service destroyed");
}
#Override
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("#### Folder watcher service initialized");
Path dir = Paths.get(PropertiesCache.getInstance().getProperty("file_input_location"));
try {
new FolderWatchService(dir).processEvents();
System.out.println("#### Folder watcher service started");
} catch (IOException e) {
System.out.println("#### Folder watcher Problem");
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
EDIT: Added what is printed out by logs
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.AprLifecycleListener
lifecycleEvent
INFO: Loaded APR based Apache Tomcat Native library 1.2.12 using APR version
1.5.2.
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.AprLifecycleListener
lifecycleEvent
INFO: APR capabilities: IPv6 [true], sendfile [true], accept filters
[false], random [true].
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.AprLifecycleListener
lifecycleEvent
INFO: APR/OpenSSL configuration: useAprConnector [false], useOpenSSL [true]
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.AprLifecycleListener
initializeSSL
INFO: OpenSSL successfully initialized (OpenSSL 1.0.2k 26 Jan 2017)
Jun 26, 2017 10:56:31 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8080"]
Jun 26, 2017 10:56:31 PM org.apache.tomcat.util.net.NioSelectorPool
getSharedSelector
INFO: Using a shared selector for servlet write/read
Jun 26, 2017 10:56:31 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-nio-8009"]
Jun 26, 2017 10:56:31 PM org.apache.tomcat.util.net.NioSelectorPool
getSharedSelector
INFO: Using a shared selector for servlet write/read
Jun 26, 2017 10:56:31 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1392 ms
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.StandardService
startInternal
INFO: Starting service Catalina
Jun 26, 2017 10:56:31 PM org.apache.catalina.core.StandardEngine
startInternal
INFO: Starting Servlet Engine: Apache Tomcat/8.5.12
Jun 26, 2017 10:56:32 PM org.apache.catalina.util.SessionIdGeneratorBase
createSecureRandom
INFO: Creation of SecureRandom instance for session ID generation using
[SHA1PRNG] took [126] milliseconds.
Jun 26, 2017 10:56:40 PM org.apache.jasper.servlet.TldScanner scanJars
INFO: At least one JAR was scanned for TLDs yet contained no TLDs. Enable
debug logging for this logger for a complete list of JARs that were scanned
but no TLDs were found in them. Skipping unneeded JARs during scanning can
improve startup time and JSP compilation time.
#### Folder watcher service initialized
The last line here is println from ContextLister, and the applic
What am I doing wrong here?

It seems that the listener implementation is blocking at new FolderWatchService(dir).processEvents();. You should run event processing in another thread (ie using a ExecutorService to submit processEvents job and maybe cancel/shutdown in contextDestroyed)

sending a cmdarray for exec to process -- hello world

Am I not sending an array of commands, "hello world ", to exec() correctly?
correct output, hello world:
thufir#mordor:~$
thufir#mordor:~$ java -jar NetBeansProjects/HelloExec/dist/HelloExec.jar
Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Main run
INFO: starting..
Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet <init>
INFO: connecting..
Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet connect
INFO: connect..
Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet connect
INFO: [echo hello 1, echo hello 2, echo hello 3]
Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet connect
INFO: did process..
Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet connect
INFO: trying..
hello 1
Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet read
SEVERE: exiting.. 0
thufir#mordor:~$
code:
package net.bounceme.mordor.telnet;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
import static java.lang.System.out;
public class Telnet {
private final static Logger LOG = Logger.getLogger(Telnet.class.getName());
public Telnet() {
LOG.info("connecting..");
}
private List<String> getCommand() {
List<String> commands = new ArrayList<>();
commands.add("echo hello 1");
commands.add("echo hello 2");
commands.add("echo hello 3");
return commands;
}
private void read(Process process) throws IOException, InterruptedException {
BufferedReader input = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line = null;
while ((line = input.readLine()) != null) {
out.println(line);
}
int exitVal = process.waitFor();
LOG.log(Level.SEVERE, "exiting.. {0}", exitVal);
}
private void connect() {
LOG.info("connect..");
Runtime runtime = Runtime.getRuntime();
List<String> cmds = getCommand();
String[] cmdArray = cmds.toArray(new String[cmds.size()]);
String command = cmdArray[0];
LOG.info(cmds.toString());
Process process = null;
try {
process = runtime.exec(command);
} catch (IOException ex) {
LOG.severe("process wrong");
Logger.getLogger(Telnet.class.getName()).log(Level.SEVERE, null, ex);
}
LOG.info("did process..");
LOG.info("trying..");
try {
read(process);
} catch (IOException | InterruptedException ex) {
LOG.severe("read wrong");
Logger.getLogger(Telnet.class.getName()).log(Level.SEVERE, null, ex);
}
}
public void tryConnect() {
connect();
}
}
crash:
thufir#mordor:~$
thufir#mordor:~$ java -jar NetBeansProjects/HelloExec/dist/HelloExec.jar
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Main run
INFO: starting..
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet <init>
INFO: connecting..
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
INFO: connect..
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
INFO: [echo hello 1, echo hello 2, echo hello 3]
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
SEVERE: process wrong
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
SEVERE: null
java.io.IOException: Cannot run program "echo hello 1": error=2, No such file or directory
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
at java.lang.Runtime.exec(Runtime.java:620)
at java.lang.Runtime.exec(Runtime.java:485)
at net.bounceme.mordor.telnet.Telnet.connect(Telnet.java:48)
at net.bounceme.mordor.telnet.Telnet.tryConnect(Telnet.java:66)
at net.bounceme.mordor.telnet.Main.run(Main.java:17)
at net.bounceme.mordor.telnet.Main.main(Main.java:11)
Caused by: java.io.IOException: error=2, No such file or directory
at java.lang.UNIXProcess.forkAndExec(Native Method)
at java.lang.UNIXProcess.<init>(UNIXProcess.java:248)
at java.lang.ProcessImpl.start(ProcessImpl.java:134)
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
... 6 more
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
INFO: did process..
Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect
INFO: trying..
Exception in thread "main" java.lang.NullPointerException
at net.bounceme.mordor.telnet.Telnet.read(Telnet.java:30)
at net.bounceme.mordor.telnet.Telnet.connect(Telnet.java:57)
at net.bounceme.mordor.telnet.Telnet.tryConnect(Telnet.java:66)
at net.bounceme.mordor.telnet.Main.run(Main.java:17)
at net.bounceme.mordor.telnet.Main.main(Main.java:11)
thufir#mordor:~$
when trying to use cmdArray:
process = runtime.exec(cmdArray);
The reasoning:
...it's because when exec is given a single string, it parses it first
(in a way that we don't like). In contrast, when exec is given a
string array, it simply passes it on to the operating system without
parsing it.
https://stackoverflow.com/a/19383655/262852

Null Pointer Exception on Session in Hibernate Java

I am creating a simple application and for some reason I keep getting null pointer exception. My guess is that it has something to do with my session.open being inside a if statement?
The error I am getting is on the finally block where it says session.close();
import java.util.*;
import javax.persistence.*;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
public class OrderTester {
private static SessionFactory sessionFactory;
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
Session session = null;
Transaction transaction = null;
System.out.println("Press 1 to log in or press 2 to sign up");
int n = scan.nextInt();
if (n == 1) {
Customer c = new Customer();
// c.logIn();
} else if (n == 2) {
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.openSession();
transaction = session.beginTransaction();
Customer c = new Customer();
Address a = new Address();
session.save(c);
session.save(a);
Scanner read = new Scanner(System.in);
System.out.println("Enter a username");
String userName = read.next();
c.setUsername(userName);
System.out.println("Enter a password");
String password = read.next();
c.setPassword(password);
System.out.println("Enter the street name");
String streetName = read.next();
a.setStreetName(streetName);
System.out.println("Enter city");
String city = read.next();
a.setCity(city);
System.out.println("Enter state");
String state = read.next();
a.setState(state);
System.out.println("Enter zipcode");
String zipcode = read.next();
a.setZipCode(zipcode);
read.close();
transaction.commit();
} catch (Exception ex) {
transaction.rollback();
System.out.println("Transaction is rolled back.");
} finally {
session.close();
sessionFactory.close();
}
}
}
}
The error:
Press 1 to log in or press 2 to sign up
2
Mar 05, 2016 4:51:44 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.5.Final}
Mar 05, 2016 4:51:44 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.11.Final}
Mar 05, 2016 4:51:44 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
Mar 05, 2016 4:51:44 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Mar 05, 2016 4:51:44 PM org.hibernate.cfg.Configuration configure
INFO: HHH000043: Configuring from resource: /hibernate.cfg.xml
Mar 05, 2016 4:51:44 PM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: HHH000040: Configuration resource: /hibernate.cfg.xml
Mar 05, 2016 4:51:45 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity
WARN: HHH000223: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!
Exception in thread "main" java.lang.NullPointerException
at Pizza.OrderTester.main(OrderTester.java:65)

A NullPointerException on that line with nothing else in the stack trace can only mean that session is null. The only way that could happen, as far as I can tell, is if the session = sessionFactory.openSession(); assignment is never executed - which would mean that an exception is happening either in sessionFactory.openSession() or in HibernateUtil.getSessionFactory(), with that exception being hidden by the later exception raised in the finally block.
I expect that if you step through this code in a debugger you will see the execution flow jump from one of those two lines to the catch block, then hit a NullPointerException on transaction.rollback() (because the transaction assignment never happened either) and jump to the finally block, where it hits another NullPointerException and bails out.

Since both session and sessionFactory are initialized as null outside the try/catch block, never assume they will not be null in finally clause and call close() directly. Change it to the following:
} catch (Exception ex) {
if(transaction != null) {
try {
transaction.rollback();
} catch (Exception e) { // Log error }
}
ex.printStackTrace();
System.out.println("Transaction is rolled back.");
} finally {
if(session != null) {
try {
session.close();
} catch (Exception e) { // Log error }
}
if(sessionFactory != null) {
try {
sessionFactory.close();
} catch (Exception e) { // Log error }
}
}

vlcj media player doesn't play video, no fail message

I have done a video player using vlcj library of vlc media player.
When i run the code the frame open fine but the video dosen't play.
Here is my code to do that..
public class Test {
public static void main (String[] args) {
JFrame f = new JFrame();
f.setLocation(100,100);
f.setSize(1000,600);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
Canvas c = new Canvas();
c.setBackground(Color.black);
JPanel p = new JPanel();
p.setLayout(new BorderLayout());
p.add(c);
f.add(p);
NativeLibrary.addSearchPath(RuntimeUtil.getLibVlcLibraryName(), "C:\\Program Files\\VideoLAN\\VLC");
Native.loadLibrary(RuntimeUtil.getLibVlcLibraryName(), LibVlc.class);
MediaPlayerFactory mpf = new MediaPlayerFactory();
EmbeddedMediaPlayer emp = mpf.newEmbeddedMediaPlayer(new DefaultFullScreenStrategy(f));
emp.setVideoSurface(mpf.newVideoSurface(c));
//emp.toggleFullScreen();
emp.setEnableMouseInputHandling(false);
emp.setEnableKeyInputHandling(false);
String file= "C:\\!temp\\v.mp4";
emp.prepareMedia(file);
}
}
This is on my console:
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.Info <init>
INFO: vlcj: 3.8.0
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.Info <init>
INFO: java: 1.8.0_65 Oracle Corporation
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.Info <init>
INFO: java home: C:\Program Files\Java\jre1.8.0_65
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.Info <init>
INFO: os: Windows 8.1 6.3 amd64
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.binding.LibVlcFactory create
INFO: vlc: 2.2.1 Terry Pratchett (Weatherwax), changeset 2.2.1-0-ga425c42
nov. 03, 2015 12:04:40 DU uk.co.caprica.vlcj.binding.LibVlcFactory create
INFO: libvlc: C:\Program Files\VideoLAN\VLC\libvlc.dll

The prepareMedia() method just gets the media 'ready', it does not actually play it.
So use play() after you prepare it, or miss prepare out and just use playMedia(...) instead.
And as per the other comment, are you sure "!temp" is correct?

neo4j logger not going to file

Have a Transaction Event Handler to do logging for changes made via the Embedded API.
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.event.TransactionData;
import org.neo4j.graphdb.event.TransactionEventHandler;
import org.neo4j.kernel.impl.util.StringLogger;
import org.neo4j.server.logging.Logger;
import java.util.logging.Level;
public class WarehouseTransactionEventHandler implements TransactionEventHandler<String> {
private static Logger log = Logger
.getLogger(WarehouseTransactionEventHandler.class);
public void afterCommit(TransactionData data, String state) {
Iterable<Node> createdNodes = data.createdNodes();
for(Node n: createdNodes) {
log.info("AfterCommit ########: created node:" + n.getId());
log.log(Level.ALL,"AfterCommit ########: created node:" + n.getId());
}
}
public void afterRollback(TransactionData data, String state) {
// TODO Auto-generated method stub
}
public String beforeCommit(TransactionData data) throws Exception {
Iterable<Node> createdNodes = data.createdNodes();
for(Node n: createdNodes) {
log.info("BeforeCommit ######: created node:" + n.getId());
log.log(Level.ALL,"BeforeCommit ######: created node:" + n.getId());
}
return null;
}
}
Then I register it in my code that does the writing
GraphDatabaseService graphDb = new EmbeddedGraphDatabase(DB_PATH)
graphDb.registerTransactionEventHandler(new WarehouseTransactionEventHandler())
// do stuff
graphDb.shutdown();
So when I run my code it seems to be working
INFO: AfterCommit ########: created node:14
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:15
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:17
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:16
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:19
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:18
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:21
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:20
Jun 26, 2013 12:24:22 PM org.neo4j.server.logging.Logger log
INFO: AfterCommit ########: created node:22
However I have gone through the logs and can't find any of these AfterCommit messages. My log.properties hasn't been changed except for setting java.util.logging.FileHandler.limit=10000000
Any thoughts? Thanks!

Have you tried using log4j, it works fine with me.
Initializing the logger # the beginning of your app, it will log your messages wherever you want it to be.. like this:
static {
try {
String logFileName = "neo4j.log";
RollingFileAppender fa = new RollingFileAppender();
fa.setName("NEO4JLOGGER");
fa.setFile(logFileName);
fa.setLayout(new PatternLayout(
"[%d{dd.MM.yyyy HH:mm:ss.SSS}] %5p %c{1}:%L - %m%n"));
fa.setAppend(true);
fa.activateOptions();
Logger.getLogger("CLASSES NEEDED TO BE LOGGED").setLevel(Level.ALL);
Logger.getLogger("CLASSES NEEDED TO BE LOGGED").addAppender(fa);
} catch (Exception ex) {
logger.error("Intialize Logger :: Failed... \n ", ex);
}
}