I have built a Spring CLI app which communicates with a server in an async fashion. The server was given, I did not create it, basically my app is required to open a TCP socket and send a JSON through it, then it sends back a JSON. It is mandatory not to use CLI parameters, but instead in the callback of the request I want to show the user a set of options for which he needs to select by inserting the corresponding number on the CLI. Most probably I'm not doing right something, because after entering the command, I see spring> on the console (this is an expected behavior) and it will block the async callback unless I press something (nothing is printed to the CLI when I receive the callback unless I press a bunch of enters - this is unexpected). To read from the console so far I used JLine's command line, what I would like to achieve is that when I get the response from the server and the callback is served, the console is given to the thread on which the callback is running (I instantly print the contents of the callback to the console, and I'm able to read the input without any tricks).
Some code:
public void runReceiver(){
receiverThread = new Thread(() -> {
byte[] digit = null;
int nb;
Iterator<CommandListener> it;
CommandListener listener;
String message;
List<CommandListener> listenersToRemove = new ArrayList<>();
while (true) {
try {
nb = communicatorInput.readInt();
digit = new byte[nb];
communicatorInput.readFully(digit);
} catch (IOException e) {
e.printStackTrace();
}
it = listeners.iterator();
while (it.hasNext()){
listener = it.next();
if (digit != null && digit.length > 0) {
message = new String(digit);
// the message was not acknowledged
if(message.contains("NACK")){
try {
listener.onError(message);
if (listener.isDone()) {
listenersToRemove.add(listener);
}
} catch (Exception e){
e.printStackTrace();
}
} else try {
listener.onCompleted(message);
} catch (InvalidObjectException e){
Main.logger.debug(String.format("Response could not be parsed as %s", listener.getCommandType()));
} catch (Exception e){
e.printStackTrace();
}
if (listener.isDone()) {
listenersToRemove.add(listener);
}
}
}
listeners.removeAll(listenersToRemove);
}
}, "receiverThread");
receiverThread.setDaemon(true);
receiverThread.start();
Then a CLI command (it expects no input here):
#CliCommand(value="start", help = "Starts stuff")
public void start() throws IOException, InterruptedException {
// this method is passed to the thread with the listener
getAvailabilities().updateAvailabilities("all", "all", "all", someListener);
}
And the callback for that listener:
someListener = new CommandListener() {
private String source = "Start some listener";
#Override
public void onCompleted(String r) throws IOException {
System.out.println("Which would you like to start?");
getAvailabilities().printAvailableBrands();
String brandNumber = "";
while(Objects.equals(brandNumber, "")){
System.out.println("Please enter the number of the Brand: ");
//when the callback arrives here I still only see ">spring:" and I get nothing printed on the console
brandNumber = cr.readLine();
if(!isInputAllowed(brandNumber, getAvailabilities().AvailableBrands.size())){
brandNumber = "";
}
}
BrandName = getAvailabilities().AvailableBrands.get(Integer.parseInt(brandNumber) - 1);
//updating the availabilities narrows down the things I list to the console, so I send an update after every selection
getAvailabilities().updateAvailabilities("all", BrandName, "all", getInterfaceListener);
done = true;
}
This might slightly connect to the issue that sometimes while debugging the CLI in Idea, it gets whacky inputs, eg. when I insert start it says No such command as ar, and if I press enter again, it'll say (some of) the rest: No such command as stt.
The problem is here:
if (listener.isDone()) {
listenersToRemove.add(listener);
}
If you want your listeners to be executed asynchronously you should not check their completion right away on the same thread as it will most likely return false.
The issue you might be having is that your listeners schedule some task but have no time to finish it as you immediately remove them after the loop:
listeners.removeAll(listenersToRemove);
It is very hard to tell what your logic is but I guess in the next while iteration your list is empty.
Related
I wish to create a continuous Enhanced For loop within a Java program to output a message from an automatic ping to a Text area, and then to stop when a condition is met (IP address is offline). I have IP addresses in a String array called 'ip'. Works fine with no loop but requires continuous iterations until no response is detected.
Tried using Boolean loop which I included with the code - however does not append text to the TextArea and gets caught in a continuous loop.
for (String ip : listOfhosts) {
boolean repeatLoop = true;
try {
InetAddress i = InetAddress.getByName(ip);
textArea.append("Sending Ping Request to " + ip + "\n");
//boolean run = true;
//while (run){
if (i.isReachable(100)) { // 1 second limit
textArea.append("Host is online \n");
} else {
textArea.append("\nHOST IS OFFLINE\n");
//System.exit(0); //If something is offline, system will close. For now.
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("email#gmail.com"));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("email#hotmail.com"));
message.setSubject("Test Mail");
message.setText("Test Mail," + "\n Sent From sendMail.java application\n");
//textArea.append("OK - Online \n");
Transport.send(message);
textArea.append("Mail Sent to email#email.com \n host " + ip + " is offline \n");
return;
} catch (MessagingException e) {
throw new RuntimeException(e);
}
}
} catch (Exception e) {
textArea.append("Unknown HOST\n");
e.printStackTrace();
}while(repeatLoop);
Gets caught in continuous loop - crashing the program. Any help would be great!
This code will block you UI. You should run it in a separate thread, and also add some delay between checks.
A simpler solution would also be to use a Timer
For instance, to check every second:
Timer timer = new Timer();
timer.schedule(new TimerTask() {
#Override
public void run() {
// your code
}
}, 1000);
There're two simple ways to break out of an enhanced for-loop in Java. One is to throw an exception, although for normal flow control this is considered exceptionally poor use of exceptions.
The other is to use break; which will break you out of the most immediate for-loop. People aren't always fond of return mid-function or break mid-for loop (or continue for that matter) as they can act a bit like goto/jump statements and reduce the clarity of your code. On the other hand, this is exactly what break is intended for, so there's no argument about misuse of the instruction.
An alternative approach is to use a normal while loop and forgo the enhanced for-loop for a normal iterator. In this case, listOfHosts.iterator(), will allow you to calculate a combination of .hasNext() and isReachable(...) to decide whether to continue looping.
// suppose listOfhosts is a String Array
List<String> srcHostList = new ArrayList<String>();
srcHostList.addAll(Arrays.asList(listOfhosts));
List<String> offlineList = new ArrayList<String>();
while( srcHostList.size() > 0) {
offlineList.clear();
for(String ip: srcHostList) {
boolean isOnline = true;
try{
// TODO check online
}catch(Exception ex){
// TODO handle exception
isOnline = false;
}
if(!isOnline) offlineList.add(ip);
}
srcHostList.removeAll(offlineList);
}
I am trying to write a chat using webcocket, for offline users I have used java Queue, If user is offline I keep messages in a Queue and when user gets online I check if Queue is empty and if it's not, using a loop i remove each messages from Queue. The problem is it just sends last message to user even though all messages are in queue,
here is my onOpen method:
#ServerEndpoint(value = "/chat/{room}/{user}", encoders = ChatMessageEncoder.class, decoders = ChatMessageDecoder.class)
public class ChatEndpoint {
private final Logger log = Logger.getLogger(getClass().getName());
private static final Map<String, Queue<ChatMessage>> userMessageBuffer = new HashMap<>();
#OnOpen
public void open(final Session session,
#PathParam("room") final String room,
#PathParam("user") final String userId) {
log.info("session openend and bound to room: " + room);
// session.getUserProperties().put("room", room);
session.getUserProperties().put("user", userId);
Queue<ChatMessage> userMsgs = userMessageBuffer.get(userId);
ChatMessage sendChat = new ChatMessage();
if (userMsgs != null && !userMsgs.isEmpty()) {
for (int i = 0; i < userMsgs.size(); i++) {
sendChat = userMsgs.remove();
System.out.println("size!!!!!! " + sendChat.getMessage());
try {
session.getBasicRemote().sendObject(sendChat);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (EncodeException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}}
Does any one knows where is the problem?
I did not check the complete code, but certainly
for (int i = 0; i < userMsgs.size(); i++)
is your problem. Because you are using i++ and checking userMsgs.size() as a condition in for loop. So you are increasing i by 1 and decreasing userMsgs size by 1, effectively you will be able access only half of the elements in the queue.
say you have 8 elements in the queue, initially (Imagine this like Admiral General Aladeen explaining about round shaped missile)
i=0 and userMsgs.size()=8
i=1 and userMsgs.size()=7
i=2 and userMsgs.size()=6
i=3 and userMsgs.size()=5
i=4 and userMsgs.size()=4 // comes out of loop.
you should use a while loop instead,
while(!userMsgs.isEmpty()){
.....
}
You said you are able to send only last message to the user, may be that is because you have only 2 messages in the queue. I know it's rare but that should be the case according your code.
I'm working on a project for school. We are are making a harbour where you can load and unload ships. The control part is made in Netbeans and the simulation in JME.
We send data from Netbeans to JME via a socket. JME is running a serversocket who is liseting to the input from Netbeans.
For example Netbeans sends an ID of a container and the crane in JME gets that container and puts it on the shore so a verhicle can pick it up.
We change a count in the main (Main.count = 2) so the SimpleUpdate can call a method. The problem is that sometimes stuff is getting skipped. Also I think it's getting worse when we send more information for instance a vehicle that's getting the container. How can I fix this? And are there other ways to get a good connection?
The code:
Netbeans
Send client
public static void run() throws Exception
{
Socket socket = new Socket("Localhost", 4321);
out = new ObjectOutputStream(socket.getOutputStream());
}
//Sent arraystring to Simulation
public void sent(String sentString){
try {
out.writeObject(sentString);
} catch (IOException ex) {
Logger.getLogger(CommunicationWithSimulatoin.class.getName()).log(Level.SEVERE, null, ex);
}
}
Main send some stuff example
for(int i = Calculator.getContainersFromMaritime(); i > 1; i--)
{
Thread.sleep(50);
sim.sent("craneCon;" + i + ";");
System.out.println(i);
}
JME
Listener
public static void Listener() throws Exception {
boolean isRunning = true;
//Creates the server socket
ServerSocket sSocket = new ServerSocket(4321);
//Acception a connection from the client
Socket socket = sSocket.accept();
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
//Get the input from the client
while (isRunning) {
//Reads and prints the input
test = (String) in.readObject();
System.out.println(test);
String[] parts = receivedString.split(";");
if(parts[0].equals("ContainerPositionsMaritime"))
{
Maritime.ContainersOnBoard = receivedString.split(";");
Main.count = 0;
}
if(parts[0].equals("craneCon"))
{
int containerId = Integer.parseInt(parts[1]);
SeagoingCranes.idContainer = containerId;
Main.count = 2;
}
}
}
Main simpleupdate
public void simpleUpdate(float tpf) {
if(count == 0)
{
InitContainers();
//martime.setLocalTranslation(0, 500.0f, 0);
count = 999;
}
if(count == 2)
{
InitCrane(SeagoingCranes.idContainer);
count = 999;
}
if(martime != null)
{
martime.move(0,0,0.25f*tpf);
}
}
There are a number of problems with your program.
Firstly - you have potential race and thread contention issues as you have "count" which I assume is an integer value inside the SimpleApplication is being modified from one thread and read from another. Unless the value is declared as volatile this can cause all sorts of unexpected problems and odd behaviour and even declaring it as volatile is not recommended.
Your main issue though (even leaving aside the subtle problems) is being caused by the fact that in simpleUpdate() you are scanning count and then taking an action based on count. simpleUpdate() is called once for each frame as your jME3 application is running.
If you receive more than one message in a frame then only the last one will be acted on as the count will be modified again before the next simpleUpdate() runs.
The best way to do this is to use app.enqueue().
if(parts[0].equals("ContainerPositionsMaritime"))
{
final ContainersOnBoard containers = receivedString.split(";");
mainApp.enqueue(new Callable<Spatial>() {
public Spatial call() throws Exception {
mainApp.InitContainers(containers);
return null;
}
});
}
}
You can remove all the existing code from your simpleUpdate().
The Callable you enqueue will be called back from the JME3 thread in the next update and process the addition of the containers. By doing a similar thing for every different commands it will enqueue and process all the commands as the time comes. You can enqueue as many commands as you like and they will all be processed.
In general you should read up on AppStates, Controls and the threading model as they will allow you to make your code much more structured and organised.
http://hub.jmonkeyengine.org/wiki/doku.php/jme3:advanced:multithreading
http://hub.jmonkeyengine.org/wiki/doku.php/jme3:advanced:application_states
http://hub.jmonkeyengine.org/wiki/doku.php/jme3:advanced:custom_controls
P.S. You should try and follow Java style/coding conventions - for example methods should begin with lowercase. initContainers not InitContainers.
I am a total newbie in JSPs/Tomcat and to a large extent in Java as well. Here's what I have to do -- when a user clicks a button/visits a URL, I want to launch a Java program (which takes some command line arguments).
I can very easily do
Runtime.exec("C:\\Python27\\python.exe test.py")
OR
Runtime.exec("java -cp %CLASSPATH%;C:\\devprojects HelloWorld"
and this works fine. Where HelloWorld.class just prints "HelloWorld".
However, when I attempt a java program which takes command line arguments, the GET request just hangs doing nothing. I don't know what logs to look for or what could be wrong here. After having spent TWO days on trying various things, I am just about to give up now.
Runtime.exec("java -cp %CLASSPATH%;C:\\devprojects Run --username Blah --password Foo");
What user does Tomcat end up running this java program as? Can I make it to be Administrator? This is on Windows 2008, does UAC interfere with things?
I cannot modify the Run.class here, I HAVE to run it as is and with command line parameters.
Please advise.
One idea: you are relying on the default tokenization of your command line as one complete String, and it is not parsing the last one as you expect. Instead you should use the form of this method that takes a String[], after you have chopped up the command line yourself:
http://docs.oracle.com/javase/6/docs/api/java/lang/Runtime.html#exec(java.lang.String[])
Or, it is waiting for input from you, or waiting for you to read its output. This could explain the hang. Search the internet for the dangers of streams and Runtime.exec().
Consider ProcessBuilder instead.
Remember also that you have to be sure that the executed file dont run "forever", and
if you need to pass some arguments, you could use this:
static String startProcess(String command, String dir) throws IOException {
StringBuffer ret = new StringBuffer();
String[] comm = new String[3];
comm[0] = COMMAND_INTERPRETER[0];
comm[1] = COMMAND_INTERPRETER[1];
comm[2] = command;
long start = System.currentTimeMillis();
try {
//Start process
Process ls_proc = Runtime.getRuntime().exec(comm, null, new File(dir));
//Get input and error streams
BufferedInputStream ls_in = new BufferedInputStream(ls_proc.getInputStream());
BufferedInputStream ls_err = new BufferedInputStream(ls_proc.getErrorStream());
boolean end = false;
while (!end) {
int c = 0;
while ((ls_err.available() > 0) && (++c <= 1000)) {
ret.append(conv2Html(ls_err.read()));
}
c = 0;
while ((ls_in.available() > 0) && (++c <= 1000)) {
ret.append(conv2Html(ls_in.read()));
}
try {
ls_proc.exitValue();
//if the process has not finished, an exception is thrown
//else
while (ls_err.available() > 0)
ret.append(conv2Html(ls_err.read()));
while (ls_in.available() > 0)
ret.append(conv2Html(ls_in.read()));
end = true;
}
catch (IllegalThreadStateException ex) {
//Process is running
}
//The process is not allowed to run longer than given time.
if (System.currentTimeMillis() - start > MAX_PROCESS_RUNNING_TIME)
//this is very important
{
ls_proc.destroy();
end = true;
ret.append("!!!! Process has timed out, destroyed !!!!!");
}
try {
Thread.sleep(50);
}
catch (InterruptedException ie) {}
}
}
catch (IOException e) {
ret.append("Error: " + e);
}
return ret.toString();
}
I've been searching for four hours and this is driving me nuts. I'm going to try keeping this short, if you need more information/code ask and I'll edit.
So I have an Android client that connects to a server using PrintWriter and BufferedReader. The way it works is it starts a new ASyncTask() to load the connection. When the connection is made, it sends a "Join" message to the server, and then loads a listen thread that has a while loop waiting for UserInput.readLine() != null, and once broken it returns a string that runs a process function that takes the string and does it's action, and reloads the listen task.
//Listener thread
class listen extends AsyncTask<Integer, Integer, Void> {
#Override
protected Void doInBackground(Integer... params) {
//Disconnect variable that's only turned true on backpress
if (!disconnect) {
try {
message = Connection.listen(); //socket object
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(Void result) {
// async task finished
if (!disconnect) {
say("INCOMMING"); //easy-made function for Toast
input(message);
}
}
}
and in that Connection:
public String listen() throws IOException {
String userInput;
while ((userInput = in.readLine()) != null) {
}
return userInput;
}
Now in my server java app, I have a thread that loads up other connection threads into an ArrayList and acts as a headquarters to dispatch messages to all child clients
In my connection:
while ((inputLine = in.readLine()) != null) {
//Tells HQ to process string, with id being who it's coming from
hq.Process(id, inputLine);
if (!connected)
break;
}
in HQ object:
public void Process(int id, String str) {
String[] msg = str.split(","); //split message
String send = " "; //string I print to console
if (msg[0].equals("join")) {
send = msg[1] + " has joined!";
parent.seats[cnew.get(id).seat] = id;
cnew.get(id).sendData();
System.out.println(id);
}
And after join, the HQ tells that connection to send that player's information to the phone
public void sendData() {
out.println("chips," + chips); // Update chip count
//give player his cards
out.println("card," + hq.parent.gameCards.getCard(10) + ","
+ hq.parent.gameCards.getCard(11));
//a cry for help to get some output on the phone
out.println("error,SAY THIS");
// out.flush(); //commented out because it didn't help at all
System.out.println("sending id " + id); //debug checker (ignore this)
}
My problem is, it worked when I connected four phones and they all sent toasts to each other.
But as soon as I changed it to send back data as soon as the player joins, I'm not getting a response in Android at all.
I can't figure out why it's not working. On server side, it's going through everything (Checked with system.prints). The connection IS made, and when I click buttons on the phone the Server is outputting it's responses. But the phone is not receiving anything -- I still don't know if the server is failing to send or the phone is failing to read. Can you see anything in the code that may be causing this? Need to see more? Or have any tips on how to debug the connection status? The listen() task is never finishing it's execution anymore.
UPDATE: So I figured out it's probably to do with my while() loop on android side, doh, probably never breaking. Stupid mistake. But I tried to add this as a tester, and still nothing:
public String listen() throws IOException {
String userInput;
while ((userInput = in.readLine()) != null) {
if (userInput.length() > 2)
break;
}
return userInput;
}
UPDATE: Next desperate update -
When I hit "back" (which sends quit msg to server that closes connection, and calls out.close and the rest.close) then I get a never ending loop of "MSG" Toast's -- The Toast that I put when an input is recognized. Is a out.close causing a block?
So it turns out, println on the server's side wasn't printing a new line -- adding + "\n" at the end of the server's messages made it go through. Why? I don't know..