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  • Should I close sockets from both ends?

    - by Roman
    I have the following problem. My client program monitor for availability of server in the local network (using Bonjour, but it does not rally mater). As soon as a server is "noticed" by the client application, the client tries to create a socket: Socket(serverIP,serverPort);. At some point the client can loose the server (Bonjour says that server is not visible in the network anymore). So, the client decide to close the socket, because it is not valid anymore. At some moment the server appears again. So, the client tries to create a new socket associated with this server. But! The server can refuse to create this socket since it (server) has already a socket associated with the client IP and client port. It happens because the socket was closed by the client, not by the server. Can it happen? And if it is the case, how this problem can be solved? Well, I understand that it is unlikely that the client will try to connect to the server from the same port (client port), since client selects its ports randomly. But it still can happen (just by chance). Right?

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  • What is the most effective way to create BigInteger instance from int value?

    - by Roman
    I have a method (in 3rd-party library) with BigInteger parameter: public void setValue (BigInteger value) { ... } I don't need 'all its power', I only need to work with integers. So, how can I pass integers to this method? My solution is to get string value from int value and then create BigInteger from string: int i = 123; setValue (new BigInteger ("" + i)); Are there any other (recommended) ways to do that?

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  • JavaMe Bluetooth service registration

    - by NoGlue
    Hello, I am trying to develope an application that offers a service via bluetooth. Everything works fine in the emulator but as soon I install it on a real device (6120/X6 Nokia) the service cannot be found. If I search for already registered services such as OBEX they are found. So I think it has something to do with the registration. This is how I register the service, all of this happens in its own thread. try { LocalDevice.getLocalDevice().setDiscoverable(DiscoveryAgent.GIAC); } catch (BluetoothStateException e) { } try { notifier = (StreamConnectionNotifier) Connector.open(m_url); ServiceRecord sr = local.getRecord(notifier); StreamConnection conn = notifier.acceptAndOpen(); } catch (IOException e) { } And this is what m_url looks like: "btspp://localhost:" + 0x1116 + ";name=BlueMatch"; Thanks for your time. Best regards

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  • Android Multithreading, creating new thread not executing rest of OnCreate

    - by Aidan
    Hi Guys, Basically I'm trying to run 2 threads within the same class at the same time. The code runs but only executes whats in run() and doesnt finish the onCreate method... anyone know why? public Camera1(){ t = new Thread(this, "My Thread"); t.start(); } public void run(){ bearing(); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); new Camera1(); makeview(); tracking(); } Thanks!

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  • Weather API to mobile platform

    - by Alex
    Hello everybody! I would like to ask from you guys/girls somebody used radar image api in MOBILE PLATFORM? I got some good provider but the user agreement don`t allow to use it in mobile platform. Even some good weather forecast API exists? (with moon phase,5-7 days forecast) and radar images ? Maybe search by US zip code?

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  • Is it okay to pass injected EntityManagers to EJB bean's helper classes and use it?

    - by Zwei steinen
    We have some JavaEE5 stateless EJB bean that passes the injected EntityManager to its helpers. Is this safe? It has worked well until now, but I found out some Oracle document that states its implementation of EntityManager is thread-safe. Now I wonder whether the reason we did not have issues until now, was only because the implementation we were using happened to be thread-safe (we use Oracle). @Stateless class SomeBean { @PersistenceContext private EntityManager em; private SomeHelper helper; @PostConstruct public void init(){ helper = new SomeHelper(em); } @Override public void business(){ helper.doSomethingWithEm(); } } Actually it makes sense.. If EntityManager is thread-unsafe, a container would have to do inercept business() this.em = newEntityManager(); business(); which will not propagate to its helper classes. If so, what is the best practice in this kind of a situation? Passing EntityManagerFactory instead of EntityManager?

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  • paintComponent on JPanel, image flashes and then disappears

    - by mark
    I have a JApplet (MainClass extends JApplet), a JPanel (ChartWindow extends JPanel) and a Grafico class. The problem is that the Grafico class instance has 2 JPanel that should show 2 images (1 for each panel) but the images are shown and after a little while they disappears: instead of them i get a gray background (like an empty JPanel). This happens for every repaint() call (that are made in the ChartWindow class) the MainClass init() contains chartwindow=new ChartWindow(); add(chartwindow) chartwindow has a Grafico instance. it's the ChartWindow's paintComponent (override) paintComponent(Graphics g) { super.paintComponent(g); Image immagineGrafico=createImage(grafico.pannelloGrafico.getWidth() ,grafico.pannelloGrafico.getHeight()); Image immagineVolumi=createImage(grafico.pannelloVolumi.getWidth() ,grafico.pannelloVolumi.getHeight()); Graphics2D imgGrafico=(Graphics2D)immagineGrafico.getGraphics(); Graphics2D imgVolumi=(Graphics2D)immagineVolumi.getGraphics(); grafico.draw(imgGrafico,imgVolumi,mouseX,mouseY); ((Graphics2D)grafico.pannelloGrafico.getGraphics()).drawImage(immagineGrafico,0,0,this); ((Graphics2D)grafico.pannelloVolumi.getGraphics()).drawImage(immagineVolumi,0,0,this); } grafico's JPanels are added this way in the ChartWindow's constructor grafico=new Grafico() ................ add(grafico.pannelloGrafico); add(grafico.pannelloVolumi); Tell me if you need more information, thank you very much :-)

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  • Strange problems with the Spring RestTemplate in Android application

    - by HarryCater
    I begin to use RESTful api of the Spring Framework in my android client application. But I have encountered with problems when I tried to execute HTTP request via postForObject/postForEntity methods. Here is my code: public String _URL = "https://noticemed.com/app/mobile/login"; public void BeginAuthorization(View view) { HttpHeaders requestHeaders = new HttpHeaders(); requestHeaders.setContentType(MediaType.APPLICATION_JSON); HttpEntity<String> _entity = new HttpEntity<String>(requestHeaders); RestTemplate templ = new RestTemplate(); templ.setRequestFactory(new HttpComponentsClientHttpRequestFactory()); templ.getMessageConverters().add(new MappingJacksonHttpMessageConverter()); ResponseEntity<String> _response = templ.postForEntity(_URL,_entity,String.class); //HERE APP CRASHES String _body = _response.getBody(); And here is a stack trace in logcat after app crashing. As you see there is no definite error message. So the question what am I doing wrong? How to fix this? May there is other way to do it?I really need a help. Thanks in advance!

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  • Using switch and enumerations as substitute for named methods

    - by MatthewMartin
    This pattern pops up a lot. It looks like a very verbose way to move what would otherwise be separate named methods into a single method and then distinguished by a parameter. Is there any good reason to have this pattern over just having two methods Method1() and Method2() ? The real kicker is that this pattern tends to be invoked only with constants at runtime-- i.e. the arguments are all known before compiling is done. public enum Commands { Method1, Method2 } public void ClientCode() { //Always invoked with constants! Never user input. RunCommands(Commands.Method1); RunCommands(Commands.Method2); } public void RunCommands(Commands currentCommand) { switch (currentCommand) { case Commands.Method1: // Stuff happens break; case Commands.Method2: // Other stuff happens break; default: throw new ArgumentOutOfRangeException("currentCommand"); } }

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  • Tomcat Http and Https on the same port

    - by Ofri Dagan
    Hi, I have a web-service endpoint and a http connector on port X. At some point this endpoint needs to switch to https, but on the same port! (I know this is not the normal way of doing things, but this is what my clients expect from an old server they are using...) Is there a way to do it in tomcat?

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  • No GPS Update retrieved? Problem in Code?

    - by poeschlorn
    Hello mates, I've got a serious problem with my GPS on my Nexus One: I wrote a kind of hello world with GPS, but the Toast that should be displayed isn't :( I don't know what I'm doing wrong...maybe you could help me getting this work. Here's my code: package gps.test; import android.app.Activity; import android.content.Context; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.os.Bundle; import android.widget.Toast; public class GPS extends Activity { private LocationManager lm; private LocationListener locationListener; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // ---use the LocationManager class to obtain GPS locations--- lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationListener = new MyLocationListener(); lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 100, 1, locationListener); } private class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { if (loc != null) { Toast.makeText( getBaseContext(), "Location changed : Lat: " + loc.getLatitude() + " Lng: " + loc.getLongitude(), Toast.LENGTH_SHORT).show(); } } @Override public void onProviderDisabled(String provider) { // TODO Auto-generated method stub } @Override public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } @Override public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } } } Theoretically there should be a new toast every 100 milliseconds, shouldn't it? Or at least, when I change my position by one meter!? I've no idea why it doesn't. I must admit I'm new to the topic, maybe I've missed something? It would be great if you could give me a hint :) nice greetings, poeschlorn

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  • Hibernate/JPA DB Schema Generation Best Practices

    - by Bytecode Ninja
    I just wanted to hear the opinion of Hibernate experts about DB schema generation best practices for Hibernate/JPA based projects. Especially: What strategy to use when the project has just started? Is it recommended to let Hibernate automatically generate the schema in this phase or is it better to create the database tables manually from earliest phases of the project? Pretending that throughout the project the schema was being generated using Hibernate, is it better to disable automatic schema generation and manually create the database schema just before the system is released into production? And after the system has been released into production, what is the best practice for maintaining the entity classes and the DB schema (e.g. adding/renaming/updating columns, renaming tables, etc.)? Thanks in advance.

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  • Testing code that uses SoftReference<T>

    - by bmargulies
    To get any code with SoftReference<T> to be fully tested, one must come up with some way to test the 'yup, it's been nulled' case. One might more or less mock this by using a 'for-test' code path to force the reference to be null, but that won't manage the queue exactly as the GC does. I wonder if anyone out can share experience in setting up a repeatable, controlled, environment, in which the GC is, in fact, provoked into collecting and nulling?

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  • Check if table exists

    - by Dmitry
    I have a desktop application with a database embedded in it. When I execute my program I need to check that specific table exists, or create it if not. Given a Connection object named conn for my database, how could I check this?

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  • Is this the right way to write a ProtocolDecoder in MINA?

    - by phpscriptcoder
    public class CustomProtocolDecoder extends CumulativeProtocolDecoder{ byte currentCmd = -1; int currentSize = -1; boolean isFirst = false; @Override protected boolean doDecode(IoSession is, ByteBuffer bb, ProtocolDecoderOutput pdo) throws Exception { if(currentCmd == -1) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); isFirst = true; } while(bb.remaining() > 0) { if(!isFirst) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); } else isFirst = false; //System.err.println(currentCmd + " " + bb.remaining() + " " + currentSize); if(bb.remaining() >= currentSize - 1) { Packet p = PacketDecoder.decodePacket(bb, currentCmd); pdo.write(p); } else { bb.flip(); return false; } } if(bb.remaining() == 0) return true; else return false; } } Anyone see anything wrong with this code? When a lot of packets are received at once, even when only one client is connected, one of them might get cut off at the end (12 bytes instead of 15 bytes, for example) which is obviously bad.

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  • What's the good of IDE's auto generated @override annotation ?

    - by Tony
    I am using eclipse , when I use shortcut to generate override implementations , there is an override annotation up there , I am using JDK 6 , this is all right , but under JDK 5 this annotation will cause an error, so I want to ask , if this annotation is completely useless ? Will compiler do some kind of optimization using this annotation ?

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  • Long running method causing race condition

    - by keeleyt83
    Hi, I'm relatively new with hibernate so please be gentle. I'm having an issue with a long running method (~2 min long) and changing the value of a status field on an object stored in the DB. The pseudo-code below should help explain my issue. public foo(thing) { if (thing.getStatus() == "ready") { thing.setStatus("finished"); doSomethingAndTakeALongTime(); } else { // Thing already has a status of finished. Send the user back a message. } } The pseudo-code shouldn't take much explanation. I want doSomethingAndTakeALongTime() to run, but only if it has a status of "ready". My issue arises whenever it takes 2 minutes for doSomethingAndTakeALongTime() to finish and the change to thing's status field doesn't get persisted to the database until it leaves foo(). So another user can put in a request during those 2 minutes and the if statement will evaluate to true. I've already tried updating the field and flushing the session manually, but it didn't seem to work. I'm not sure what to do from here and would appreciate any help. PS: My hibernate session is managed by spring.

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  • Spring, Hibernate and Ehcache - Wrong entities

    - by asrijaal
    Hi there, I've got a webapp which uses spring+hibernate for my data layer. I'm using 2nd level caching with ehcache as provider. Everything seems to work so far but sometimes we encounter a problem which I can't really figure out atm. One of my tables is used for labels within the application - every user who logs access this table with his set language. Works for 90% of the time. But sometimes the user gets labels for the wrong language, e.g. instead of german everything turns to italian. After a logout and login all labels are correct. Does anyone of you encountered something like this? I'm not sure where to look at: spring+hibernate+ehcache is a solid package or is it not? Cheers

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  • AtomicInteger lazySet and set

    - by Yan Cheng CHEOK
    May I know what is the difference among lazySet and set method for AtomicInteger. javadoc doesn't talk much about lazySet : Eventually sets to the given value. It seems that AtomicInteger will not immediately be set to the desired value, but it will be scheduled to be set in some time. But, what is the practical use of this method? Any example?

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  • Better product to develop for, iPad or Android based tablet in a purely business related application

    - by Caylem
    Hey guys Just wondering what you'd suggest as the best platform for developing a business application for a tablet device. The application needs to be multitouch, have access to a maps API, a database on the device. It will not be going on sale in the app store or Androids market, it is purely for specific business task and not for the general consumer. Obviously the options seem to be iPhone OS and the iPad or Android and an Android tablet device. The form factor for the end product requires something in the region of 8 inch+ screen and enough processing power to provide a good experience for the end user. Any help would be much appreciated. Thanks

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  • JAXB doesn't unmarshal list of interfaces

    - by Joker_vD
    It seems JAXB can't read what it writes. Consider the following code: interface IFoo { void jump(); } @XmlRootElement class Bar implements IFoo { @XmlElement public String y; public Bar() { y = ""; } public Bar(String y) { this.y = y; } @Override public void jump() { System.out.println(y); } } @XmlRootElement class Baz implements IFoo { @XmlElement public int x; public Baz() { x = 0; } public Baz(int x) { this.x = x; } @Override public void jump() { System.out.println(x); } } @XmlRootElement public class Holder { private List<IFoo> things; public Holder() { things = new ArrayList<>(); } @XmlElementWrapper @XmlAnyElement public List<IFoo> getThings() { return things; } public void addThing(IFoo thing) { things.add(thing); } } // ... try { JAXBContext context = JAXBContext.newInstance(Holder.class, Bar.class, Baz.class); Holder holder = new Holder(); holder.addThing(new Bar("1")); holder.addThing(new Baz(2)); holder.addThing(new Baz(3)); for (IFoo thing : holder.getThings()) { thing.jump(); } StringWriter s = new StringWriter(); context.createMarshaller().marshal(holder, s); String data = s.toString(); System.out.println(data); StringReader t = new StringReader(data); Holder holder2 = (Holder)context.createUnmarshaller().unmarshal(t); for (IFoo thing : holder2.getThings()) { thing.jump(); } } catch (Exception e) { System.err.println(e.getMessage()); } It's a simplified example, of course. The point is that I have to store two very differently implemented classes, Bar and Baz, in one collection. Well, I observed that they have pretty similar public interface, so I created an interface IFoo and made them two to implement it. Now, I want to have tools to save and load this collection to/from XML. Unfortunately, this code doesn't quite work: the collection is saved, but then it cannot be loaded! The intended output is 1 2 3 some xml 1 2 3 But unfortunately, the actual output is 1 2 3 some xml com.sun.org.apache.xerces.internal.dom.ElementNSImpl cannot be cast to testapplication1.IFoo Apparently, I need to use the annotations in a different way? Or to give up on JAXB and look for something else? I, well, can write "XMLNode toXML()" method for all classes I wan't to (de)marshal, but...

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