ok so i've nearly got this. But it seems there is some logic error that i can't get around. Note that i cannot use try/catch. No need to ask why
EDIT
for(String File : List){
final String FilePath = getPath() + "/" + File;
Render renderer = renderFile(FilePath);
Runtime.getRuntime().addShutdownHook(new Thread(){
public void run() {
deleteFile(FilePath);
}
});
deleteFile(FilePath);
updateReport(stuff);
writeReportToFile(Report.toString());
I want it to delete the file that's causing my crash .. if the app crashes but it doesn't seem to be working. Am i calling it wrongly or what? confused
FINAL EDIT
OK after much toying around i finally got it to work!! Thanks everyone
From your last question I see, that you
process images,
one or more images will crash the JVM,
we can't catch that exception/error and
we want to delete the corrupt image on the next run
An easy solution goes like that:
Each time, before you read bytes from an image file, persist the name of that image to a file (like: processingImage.txt)
Each time, an image has been processed succesfully, delete processingImage.txt
If the application crashes, then processingImage.txt contains the name of the offending image
If you start the application, check if processingImage.txt exists, read the name of the image, delete the image and delete processingImage.txt.
I have a bad feeling about this, but you could add a shutdown hook on your application. (Be warned, while the shutdown hooks are processed, the only way to kill your application is via task manager - so be sure that your shutdown hook really works/does not take forever/does not cause deadlocks)
The following main
public static void main(String[] args) {
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("I'm called on shutown.");
}
});
throw new RuntimeException("Uncaught Exception");
}
prints this:
Exception in thread "main" java.lang.RuntimeException: Uncaught Exception
at stackoverflowtests.ShutdownHookTester.main(ShutdownHookTester.java:11)
I'm called on shutown.
Related
I am making a personal planning program. I utilize XML documents to store user data and login data. This does not utilize a server and all accounts created in the program are localized to the computer it is stored on (in the XML documents.)
In the login XML document, I keep track of the users that are logged in so that one user can't have two windows at the same time to prevent any conflicts with data. This feature runs smoothly and I have no problem with it.
The only thing I want to know is if there is some way to catch an unexpected shut down of a program (such as a task-manager close or a forced close when shutting down the computer) so that I can "log" the user off of the XML document. Otherwise the user would never be able to get back on after an unexpected program close without going into the XML document and deleting the username from the logged in list.
It seems a shutdown hook does not work well with the event queue for a java GUI. much like this thread
I tried setting up my code exactly as shown and the shutdown hook doesn't work for me either. Are there any suggestions for ways of catching an unexpected shutdown without shutdown hooks?
this is my code:
import java.awt.EventQueue;
public class Gui {
private static Controller controller;
public static void main (String[] args) {
controller = new Controller();
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
controller.saveState();
controller.logUserOut();
}
});
EventQueue.invokeLater(
new Runnable() {
public void run() {
controller.start();
}
});
}
}
This is a closer look at my controller that logs the user out
public void logUserOut() {
loginDatabase.logUserOut(username);
saveLoginState();
}
All loginDatabase does is removes that username from the list of logged in users so that user is free to log in again
public void saveLoginState() {
XStream xStream = new XStream(new DomDriver());
OutputStream outFile;
try {
String filePath = "data" + File.separator + "loginDatabase.xml";
outFile = new BufferedOutputStream(new FileOutputStream(filePath));
xStream.toXML(loginDatabase, outFile); // This writes your state to the outputFile;
outFile.close(); //close the writer
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
This is my process for writing on the login state xml file. I suspect it might be too long for a Shutdown Hook even if it were actually being called as I expect.
Any suggestions? I thought for a long time about possibly using simple variables to solve the problem but because I have the program set so that the user can be logged into multiple accounts, the use of variables is impossible.
Also, will the controller object contained in the scope of the shutdown hook be the same controller that is modified in the event queue scope?
The shutdown hook can be a solution here. For details see e.g. this answer: https://stackoverflow.com/a/2541618/2045440
[Off topic] However, if you're at risk that unexpected termination of your application can result in lost of important data, maybe it would be worth to consider the more persistent way of processing this data (autosaving, backup files etc).
I resolved the problem by checking the task manager of the operating system. It allowed me to see if the user the xml document said was logged in actually had a program open. If not then I knew there was a problem. This is a fix for my particular program but it might be a help for others as well.
The link to that thread is here.
I know this is an error with accessing memory outside the readspace but i have absolutely no idea how to fix this. I'm new to android, so i don't exactly know how to print out a more detailed error list from logcat in eclipse. I've tried everything from disposing literally everything, to calling System.gc to setting all my variables to null. However, whenever i switch screens the fatal signal occurs. I just need someone to tell me what exactly is going on or how i could get more details about the error.
I had the same error, what solved it was to make sure i'm on the UI thread, like this:
Gdx.app.postRunnable(new Runnable() {
#Override
public void run() {
// Your crashing code here
}
});
In my case i received same error when i try to create a new body and attach it's fixture, from beginContact (inside Contact Listener). After i moved outside Contact Listener my body creation everything was ok. Probably some conflict appears in Fixture createFixture (FixtureDef def) because according to manual: Contacts are not created until the next time step.
In JME I try to use threading but when I run the program the function never starts.
I have a server socket who is listening to input from Netbeans.
Listener
while (isRunning) {
//Reads and prints the input
String receivedString = (String) in.readObject();
System.out.println(receivedString);
String[] parts = receivedString.split(";");
if(parts[0].equals("craneCon"))
{
final int containerId = Integer.parseInt(parts[1]);
m.enqueue(new Callable<Spatial>(){
public Spatial call() throws Exception{
m.removeContainersFromMaritime(containerId);
return null;
}
});
}
So in the main there is the function removeContainersFromMaritime
public void removeContainersFromMaritime(final int idContainer)
{
Node container = Maritime.listOfContainers.get(idContainer);
martime.detachChild(Maritime.listOfContainers.get(idContainer));
seagoingcrane.attachChild(Maritime.listOfContainers.get(idContainer));
container.setLocalTranslation(0,5,0);
System.out.println(Maritime.listOfContainers.get(0).getWorldTranslation().z);
}
The connection is alright but the method is never executed. How can I fix this?
jMonkeyEngine uses a swing-style threading model where there is a single render thread that does all the work. Any changes to the scene graph have to be done from that render thread.
To get into the render thread you can implement AppStates, Controls or you can enqueue Callables which are then executed on the render thread in a similar way to Swing's invokeLater.
The code snippet you posted looks about right, so assuming m is your running jME3 SimpleApplication then m.enqueue() will cause the enqueued callable to be executed next time around the render loop (i.e. at the start of the next frame).
If you are not seeing it executed then either:
Your application is not running
You created more than one application and enqueued it to the wrong one
The code is actually running and you just think it isn't.
Stepping through the code in the debugger and/or adding debug statements (for example breakpoint inside removeContainersFromMaritime to see if it is actually called should allow you to narrow this down.
I might be missing something but what is "m" in m.enqueue(...)?
I'm guessing it is an executor service of some sort and it's probably where the problem lies.
You could try instead:
new Thread() {public void run()
{
m.removeContainersFromMaritime(containerId);
}}.start();
It will at least show you if the problem is coming from "m" as an executor.
I did this program that opens multiple link with default browser:
ArrayList<String> linkList = new ArrayList<>();
for (int i = 0; i < linkList.size(); i++) {
ClassRunnable_OpenLink obj = new ClassRunnable_OpenLink ( linkList.get(i) );
Thread thread = new Thread(obj);
thread.start();
}
private class ClassRunnable_OpenLink implements Runnable {
private URL link;
private String string;
public ClassRunnable_OpenLink (String string) {
this.string = string;
}
private void OpenWithBrowser () {
try {
link = new URL ( string );
edu.stanford.ejalbert.BrowserLauncher launcher = null;
try {
launcher = new BrowserLauncher(null);
} catch ( BrowserLaunchingInitializingException | UnsupportedOperatingSystemException ex) { }
launcher.openURLinBrowser( link );
} catch ( MalformedURLException ex | IOException | URISyntaxException ex) { }
}
#Override
public void run() {
OpenWithBrowser( );
}
}
This works great only if browser (say it's firefox) is already opened, but if it's not, my program only opens the first link and then I have a firefox message that tells me the the browser is still running so I need to close it first.
Same thing with chromium.
So I thought, if I had a way to check when the browser is closed I could use ProcessBuilder to open new firefox process, but I don't know if it's the best way to do this. Besides my java program allows user to select default browser so it could be complicated to use ProcessBuilder in that case.
So do you a have any idea to solve my problem? Maybe I could set a delay between each Thread in this way the system has the time to execute browser process first time, then opening first link and after the browser is running, opening other links, but how about the delay time in seconds? I'm not able to know the time that browser needs to open so it's not a good idea.
I hope you can help me. Thanks
Since java 6 you don't have to use 3rd party implementations to open a webpage with the standard browser. Try
java.awt.Desktop.getDesktop().browse(uri);
Since this maps to the underlying OS functions chances are high multiple calls will work as expected.
A workaround to this (without knowing your exact expectations), could be to do the following:
After first URL open, you could build a delay of for example 10 seconds.
Then in any consecutive URL openings, you can assume that the browser is now surely open, and start opening the next URL's fast after each other.
One note though: Always add some delay to opening URL's (not sure if your framework already does this), because else the browser might crash from the number of URL openings.
UPDATE: You say that Thread.sleep() causes your program to block, this should never happen.
You should always seperate long-during actions from the rest of your program (The (Graphical) User Interface).
So it would be better to write your 'URL opener facility' in another thread.
You can read more about that here: http://docs.oracle.com/javase/tutorial/essential/concurrency/
I'm making a desktop application which watches a folder using watchservice from java.nio.file . But I need the gui to be loaded before I start watching, because the path to be watched is in a JFieldText on the UI.
public class FileArchiverApp extends SingleFrameApplication {
static FileArchiverView gui;
#Override protected void startup() {
gui = new FileArchiverView(this); //HERE0 I have to wait for this.
show(gui);
...
public static void main(String[] args) throws IOException {
launch(FileArchiverApp.class, args);
....
WatchService watcher = FileSystems.getDefault().newWatchService();
// HERE1 while(gui==null) System.out.println("hi") ;
try {
Path dir = Paths.get(gui.getOriginPath()); // HERE2 I get nullpointer if gui was not ready
WatchKey key = dir.register(watcher, ENTRY_CREATE );
} catch ( Exception x) {
System.err.println(x);
}
while(true){ /*wait for new file event loop*/ }
}
The function getOriginPath() returns the getText() form the text field I mentioned.
In HERE0 is the attribution I mentioned. I get a nullpointer in HERE2 if gui wasn't ready.
I've tried things. If I put that thing in HERE1 it works, but of course I don't want to do that.
How could I make it?
And its taking to long(like two seconds) or the gui to stop being null with this HERE1 I don't know if it is because of the println, but I was expecting it to be almost instantaneous. Is it normal?
Thanks.
Given the limited information posted, I have to make some assumptions. Assumption 1 is that you give the JTextField a default value and use that as the path to the file you wish to watch. Assumption 2 is that you have not coded with an eye towards MVC-like design.
If both are correct, then it sounds like you have the tail wagging the dog -- the view holding the critical data, not the model. Why not fix your problem by going towards MVC and not getting the critical data from the view but rather from the model. Start the model up first thing, including getting the default path from your program Properties, get your listener going, start your view, and then if the view asks the controller to change the watched file, have the controller change the model. And then listeners in the model will notify your any observers of change.