I am making a program that communicates data through a resource folder within a network. There are two "types" of this same program, a runner and a viewer. The runner saves data and the viewer loads data. I am using OOS and OIS to do this. The runner saves the data to the resource every few seconds, and the viewer loads the data from the folder every few seconds as well. After some time between 10-80 minutes (as I have found), I get an EOFException when using a shared network, but in the Eclipse IDE, it runs smoothly for an indefinite time.
I don't know why this is. The first thing I did was move the load function to a separate thread, but that didn't help. Then I tried resetting the Thread every 10 minutes, that didn't work either. Would this solution even theoretically work or is there another glaring error in my logic.
Please ask if you need any more information.
Code for loading data through resetting Thread:
LinkedList<Thread> threads = new LinkedList<>();
Timer resetTimer = new Timer();
resetTimer.schedule(new TimerTask() {
#Override
public void run() {
try {
threads.clear();
threads.add(new Thread(new Runnable(){
public void run(){
Timer loadDataClock = new Timer();
loadDataClock.schedule(new TimerTask() {
#Override
public void run() {
try {
loadData();
} catch (Exception e) {
advancedStackTrace(e, 1);
}
}
}, 0, 5000);
}
}));
threads.get(0).start();
} catch (Exception e) {
e.printStackTrace();
}
}
}, 0, 10 * 60 * 1000);
(This works by adding Threads to a linked list every 10 minutes and clearing the LinkedList every 10 minutes and replacing it with a new Thread)
Code for loading in saving data within a DataHandler class:
public static void save(Serializable data, String filename) throws IOException {
haltLoad = true;
try {
try (ObjectOutputStream oos = new ObjectOutputStream(Files.newOutputStream(Paths.get(filename + "_fir")))) {
oos.writeObject(data);
try {
Path source = Paths.get(filename + "_fir");
Path target = Paths.get(filename);
Files.copy(source, target, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
haltLoad = false;
}
public static Object load(String filename) throws ClassNotFoundException, IOException {
if (!haltLoad) {
try (ObjectInputStream ois = new ObjectInputStream(Files.newInputStream(Paths.get(filename)))) {
return ois.readObject();
} catch (Exception e) {
return null;
}
} else {
return null;
}
}
(As a note, the variable haltLoad prevents loading while the save method is being called)
Related
I'm using the ReadData class from https://github.com/iota-community/java-iota-workshop/blob/master/src/main/java/com/iota/ReadData.java to retrieve a message from the Iota Tangle (essentially a distributed Network) via a hash value (the bundlehash).
That's my method:
private String readMessageFromHash(String BundleHash) {
final String[] s = new String[]{""};
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
try {
s[0] = ReadData.getTMessage(BundleHash);
} catch (Exception e) {
e.printStackTrace();
}
}
});
thread.start();
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
return s[0];
}
I need the return value in my next line of code but without multithreading my program crashes.
With mutlithreading it sometimes works, but most of time it doesn't work (returns an empty String).
I tried using:
thread.start();
try {
while(s[0].length < 1){}
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
return s[0];
but it just loops infinitely.
I think the issue is my program not waiting long enough for a response from the network.
I am trying to check if internet is on or not constantly every 5 seconds, I wrote below code but some how it always go inside wait() and waiting infinite.
Code I wrote :
Socket socket = null;
public void checkInternetConnectivity() throws InterruptedException {
boolean reachable = false;
ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
service.scheduleAtFixedRate(new Runnable() {
#Override
public void run() {
try {
socket = new Socket("xxx.xxx.xxx.x", xx);
} catch (UnknownHostException e) {
stopApp();
} catch (IOException e) {
stopApp();
}
}
}, 0, 5, TimeUnit.SECONDS);
synchronized (this) {
wait();
}
}
private void stopApp() {
System.out.println("Internet Not Available stopping app");
System.exit(0);
}
It always stuck inside below :
synchronized (this) {
wait();
}
You could do:
InetAddress.isReachable
Depending on what your needs are you should consider trying reach a specific host by
private static boolean googleIsAvailable() {
try {
final URL url = new URL("http://www.google.com");
final URLConnection connection = url.openConnection();
connection.connect();
connection.getInputStream().close();
return true;
} catch (MalformedURLException e) {
throw new RuntimeException(e);
} catch (IOException e) {
return false;
}
}
If your are communicating with a webservice the webservice should provide a GET method to check if it is available.
If you need to check constantly try somthing like
Socket s = new Socket(SERVER_ADDRESS, TCP_SERVER_PORT);
while(s.isConnected()){
//do your stuff
}
You should also check out the keepAlive Option.
But the more important question is what happen in your application if internet connection is not available anymore?
Most methods throw Exceptions if a Server is not available anymore.
You could just catch them and react on it.
I'm currently writing a client-server application where data should be transferred to the server to process the data. For building the connection I use ServerSocket and Socket and for sending the data I use OutputStream + ObjectOutputStream on the client-side and InputStream + ObjectInputStream on the server-side. The connection is currently running on localhost.
The object I try to transfer is a serializable class that only contains String parameters.
The problem I'm facing now is that readObject() immediately throws an EOFException as soon as the OutputStreams of the client are initialized (which leads to an initialization of the InputStreams of the server at the same time) instead of waiting for input from the client.
I send the data from the client using this code:
public void send(DataSet dataSet) {
if (!clientStreamsEstablished) {
initiateClientStreams();
}
try {
out.writeObject(dataSet);
} catch (IOException e) {
e.printStackTrace();
}
}
This method is only called when I hit the "submit"-button in the UI so it will not be executed on start of the application.
The data is currently (already tried a ton of other approaches with and without while() loop etc., etc.) read on the server using this method:
private void waitForInput(ObjectInputStream in, InputStream listeningPort) {
boolean dataReceived = false;
DataSet dataSet = null;
System.out.println("waiting ...");
while (!dataReceived) {
try {
Object temp = in.readObject(); // <-- EOFException is thrown here
boolean test = false;
if (temp instanceof DataSet) {
dataSet = (DataSet) temp;
}
} catch (ClassNotFoundException | IOException e) {
e.printStackTrace();
break;
}
}
System.out.println("Test 2: " + dataSet.toString());
if (dataReceived) {
waitForInput(in, listeningPort);
}
}
As soon as the client thread on the server reaches this line (see code-comment above) I get this stacktrace:
java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2626)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1321)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373)
at com.labdashboardserver.ClientThread.waitForInput(ClientThread.java:53)
at com.labdashboardserver.ClientThread.run(ClientThread.java:43)
Exception in thread "Thread-2" java.lang.NullPointerException
at com.labdashboardserver.ClientThread.waitForInput(ClientThread.java:65)
at com.labdashboardserver.ClientThread.run(ClientThread.java:43)
The reason for the second part of the stacktrace containing the NullPointerException is apparent as due to the EOFExcpetion the dataSet never is initialized.
However from my point of view readObject() should block and wait for the client to send ANY data before starting to read it and throw an EOF. I feel like I read through half of Stack Overflow and other forums searching for an answer but the articles I found only discuss reading files or only immediate temporary streams which are closed afterwards.
Edit
I initialize the connection before calling the UI in my main method:
public static void main(String[] args) {
connector = new LabConnector();
connector.run();
if (connector.getConnectionEstablished()) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
frame = new LabUI();
frame.setVisible(true);
} catch (Exception e) {
JOptionPane.showMessageDialog(null,
"Error Message:\n" + e.getMessage() + "\nProgram shutting down!", "Critical Error", 0);
}
}
});
}
While in the LabConnector class I initialize the streams and connection like this:
public void run() {
try {
establishConnection();
} catch (UnknownHostException e) {
retryConnection(e);
} catch (IOException e) {
retryConnection(e);
}
if (connectionEstablished) {
initiateClientStreams();
}
}
private void establishConnection() throws UnknownHostException, IOException {
client = new Socket(HOST_IP_ADRESS, HOST_PORT);
JOptionPane.showMessageDialog(null, "Connected to Server!");
connectionEstablished = true;
}
private void initiateClientStreams() {
try {
sendingPort = client.getOutputStream();
out = new ObjectOutputStream(sendingPort);
clientStreamsEstablished = true;
} catch (IOException e) {
e.printStackTrace();
}
}
I've written a springboot application to perform etl from data source to another data lake every 15 mins. I've scheduled the execution using #Scheduled annotation to a function.
I had created jar and was executing directly through java -jar ingest.jar. It works fine for some days (3-4 days). And just pauses without any exception. To resume, I have to go and press any key to make it active again.
#Scheduled(initialDelayString = "${ingest.initialdelay.in.seconds}000", fixedRateString = "${ingest.rate.in.seconds}000")
public void ingestData(){
// Ingestion Logic
}
Because the problem persisted, I created war and deployed to the tomcat server. But the problem still remains.
Can somebody point me what am I missing here? The same application works fine if I deploy to cloudfoundry.
IO Streams - FileInputStream and FileOutputStream
Helper Functions for IO
public static void saveLastSuccessfulDate(String filepath, String propertyName, Date dateTime) {
Properties prop = new Properties();
OutputStream output = null;
try {
String lastDate = getDateInFormat(dateTime);
log.info("Saving: " + lastDate);
output = new FileOutputStream(filepath);
prop.setProperty(propertyName, lastDate);
prop.store(output, null);
} catch (IOException io) {
io.printStackTrace();
} finally {
if (output != null) {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//Helper to Write to properties file
public static String checkLastSuccessfulDateAsString(String filepath, String propName) {
Properties prop = new Properties();
InputStream input = null;
try {
input = new FileInputStream(filepath);
// load a properties file
prop.load(input);
String lastSuccesfulDate = prop.getProperty(propName);
log.info("Last Successful Date: "+lastSuccesfulDate);
return lastSuccesfulDate;
} catch (FileNotFoundException f) {
log.error("checkLastSuccessfulDateAsString: File Not Found: " + f.getMessage());
} catch (IOException ex) {
log.error(ex.getMessage());
ex.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
Regards
In default, spring #Scheduled use single thread. So, if one task was blocking, the next task won't run.
You can make your task class implements SchedulingConfigurer.It will use multithread to run task and avoid blocking. Code like it:
#Component
public class TaskService implements SchedulingConfigurer {
#Override
public void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) {
scheduledTaskRegistrar.setScheduler(taskExecutor());
}
#Bean(destroyMethod = "shutdown")
public ScheduledExecutorService taskExecutor() {
return Executors.newScheduledThreadPool(100);
}
// your code
#Scheduled(initialDelayString = "${ingest.initialdelay.in.seconds}000", fixedRateString = "${ingest.rate.in.seconds}000")
public void ingestData(){
// Ingestion Logic
}
}
May help you.
I recently started learning android development (am new to java as well) and I am currently working on a chat/messenger application
The problem I am facing, as the title says, is that the listview in which the messages are shown does not update on the device, unless scrolled, but it works fine on the virtual machine. I only tested on LG Optimus l5 II so far, but i need to fix this anyway.
I think it has something to do with multithreading, because this didn't happen until i added some new threads, so the adapter for listview, android manifest and rest I say are set up correctly. I can add them if it helps.
The 2 threads i added that might cause this:
Checks the connection status and if disconnected tries to reconnect.
The thread used for communicating with the server.
I tested running only with the second thread on, and the problem still occurs.
I want to specify this is the first time I try something like this (servers-client, multithreading, java, android (I'm still in college and they don`t teach us these kinds of stuff there) ), and had no documentation ahead regarding how I should set up the communication between the server and the client. This is the most efficient way I could think of.
this is at the end of onCreate:
StartConnectingRoutine(); // so you know where it all starts
and the code for it:
private void StartConnectingRoutine()
{
Thread t = new Thread()
{
#Override
public void run()
{
while(true)
{
if(!connected)
{
if( connect != null)
{
if(!connect.isAlive())
{
ConnectListener();
}
}
else
{
ConnectListener();
}
}
try {
sleep(CONNECTION_CHECK_TIME_MS); // this is set to 10000 (10 seconds)
} catch (InterruptedException e) {
Log.e("Intrerrupted", e.toString());
}
}
}
};
t.start();
}
and the connectListener():
private void ConnectListener()
{
Log.d("Connecting", "Connecting...");
connect = new Thread()
{
JSONObject info = new JSONObject();
String receivedMessage;
#Override
public void run()
{
try {
info.put("Name", user.GetName());
info.put("PORT", MY_PORT);
info.put("IPv4", getIpAddress());
} catch (JSONException e1) {
Log.e("JSON", "JSON error: " + e1.toString());
}
try
{
ServerSocket = new Socket(SERVER_IP, SERVER_PORT);
dis = new DataInputStream(ServerSocket.getInputStream());
dos = new DataOutputStream(ServerSocket.getOutputStream());
dos.writeUTF(info.toString());
dos.flush();
String response = dis.readUTF();
if(response.equals("connected"))
{
Log.d("Connect", "Connected!");
connected = true;
}
else
Log.d("Connect", "Failed to connect!");
while(connected)
{
receivedMessage = dis.readUTF();
DisplayNewMessage(new MMessage(receivedMessage, MMessage.MessageType.Received));
}
}catch(SocketException e)
{
try {
if(connected)
{
ServerSocket.close();
dis.close();
dos.close();
connected = false;
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
catch(Exception e)
{
Log.d("Connect", "Failed to connect");
Log.e("Connect", e.toString());
connected = false;
}
}
};
connect.start();
}
Fixed:
Reconnecting thread (i tried using asyncTask for this too, but it wouldn`t open the other asyncTask, even if I tried to open it from onProgressUpdate()-which it is supposed to be able to run ui thread components):
private void startConnectingRoutine()
{
Thread t = new Thread()
{
#Override
public void run()
{
Log.d("ConnectingRoutine", "Started connecting routine.");
while(true)
{
if(!connected)
{
startListener();
}
try {
sleep(CONNECTION_CHECK_TIME_MS);
} catch (InterruptedException e) {
Log.e("Intrerrupted", e.toString());
}
}
}
};
t.start();
}
Listener thread:
private void startListener()
{
new Listener().execute();
}
.
private class Listener extends AsyncTask<Long, String, Long>
{
#Override
protected Long doInBackground(Long... params) {
Log.d("Connecting...", "Connecting...");
JSONObject info = new JSONObject();
String receivedMessage;
try {
info.put("Name", user.GetName());
info.put("PORT", MY_PORT);
info.put("IPv4", getIpAddress());
} catch (JSONException e1) {
Log.e("JSON", "JSON error: " + e1.toString());
}
try
{
serverSocket = new Socket(SERVER_IP, SERVER_PORT);
dis = new DataInputStream(serverSocket.getInputStream());
dos = new DataOutputStream(serverSocket.getOutputStream());
dos.writeUTF(info.toString());
dos.flush();
String response = dis.readUTF();
if(response.equals("connected"))
{
Log.d("Connect", "Connected!");
connected = true;
}
else
Log.d("Connect", "Failed to connect!");
while(connected)
{
receivedMessage = dis.readUTF();
publishProgress(receivedMessage);
}
}
catch(Exception e)
{
Log.d("Connect", "Failed to connect");
Log.e("Connect", e.toString());
return null;
}
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
displayNewMessage(new MMessage(values[0], MMessage.MessageType.Received));
}
#Override
protected void onPostExecute(Long result) {
super.onPostExecute(result);
connected = false;
try{
if(serverSocket != null)
serverSocket.close();
if(dis != null)
dis.close();
if(dos != null)
dos.close();
}catch(Exception e)
{
Log.e("Listener", "There was a problem closing the connection: " + e.toString());
}
}
}
There are perhaps multiple things going wrong here, but two that jump out are:
You're calling DisplayNewMessage() from outside the UI thread.
You're not notifying the adapter that its dataset has changed.
I urge you to look in to better mechanisms for executing tasks in the background than simply creating a Thread. Using AsyncTasks would be a good start, but you'll need to take special care to handle tasks between configuration changes (such as rotating the device).
Furthermore, your code is very difficult to read as you capitalize your method names. This is against Java code conventions. You will make things easier for yourself by formatting your code neatly (a good IDE helps with that) and learning to follow conventions!