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  • java.io.StreamCorruptedException: invalid stream header: 7371007E

    - by Alex
    Hello, this is pprobably a simple question . I got a client Server application which communicate using objects. when I send only one object from the client to server all works well. when I attempt to send several objects one after another on the same stream I get StreamCorruptedException. can some one direct me to the cause of this error . Thanks client write method private SecMessage[] send(SecMessage[] msgs) { SecMessage result[]=new SecMessage[msgs.length]; Socket s=null; ObjectOutputStream objOut =null; ObjectInputStream objIn=null; try { s=new Socket("localhost",12345); objOut=new ObjectOutputStream( s.getOutputStream()); for (SecMessage msg : msgs) { objOut.writeObject(msg); } objOut.flush(); objIn=new ObjectInputStream(s.getInputStream()); for (int i=0;i<result.length;i++) result[i]=(SecMessage)objIn.readObject(); } catch(java.io.IOException e) { alert(IO_ERROR_MSG+"\n"+e.getMessage()); } catch (ClassNotFoundException e) { alert(INTERNAL_ERROR+"\n"+e.getMessage()); } finally { try {objIn.close();} catch (IOException e) {} try {objOut.close();} catch (IOException e) {} } return result; } server read method //in is an inputStream Defined in the server SecMessage rcvdMsgObj; rcvdMsgObj=(SecMessage)new ObjectInputStream(in).readObject(); return rcvdMsgObj; and the SecMessage Class is public class SecMessage implements java.io.Serializable { private static final long serialVersionUID = 3940341617988134707L; private String cmd; //... nothing interesting here , just a bunch of fields , getter and setters }

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  • Question about decorator pattern and the abstract decorator class?

    - by es11
    This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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  • Improving field get and set performance with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • Problem when trying to connect to a desktop server from android on wifi

    - by thiagolee
    Hello, I am trying to send a file from the phone running Android 1.5 to a server on a desktop. I wrote some code, which works on emulator, but on the phone it doesn't. I'm connecting to the network through WiFi. It works, I can access the internet through my phone and I've configured my router. The application stops when I'm trying to connect. I have the permissions. Someone have any ideas, below is my code. Running on Android package br.ufs.reconhecimento; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.net.Socket; import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.content.Intent; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.EditText; import android.widget.ImageButton; /** * Sample code that invokes the speech recognition intent API. */ public class Reconhecimento extends Activity implements OnClickListener { static final int VOICE_RECOGNITION_REQUEST_CODE = 1234; static final String LOG_VOZ = "UFS-Reconhecimento"; final int INICIAR_GRAVACAO = 01; int porta = 5158; // Porta definida no servidor int tempoEspera = 1000; String ipConexao = "172.20.0.189"; EditText ipEdit; /** * Called with the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Inflate our UI from its XML layout description. setContentView(R.layout.main); // Get display items for later interaction ImageButton speakButton = (ImageButton) findViewById(R.id.btn_speak); speakButton.setPadding(10, 10, 10, 10); speakButton.setOnClickListener(this); //Alerta para o endereço IP AlertDialog.Builder alerta = new AlertDialog.Builder(this); alerta.setTitle("IP");//+mainWifi.getWifiState()); ipEdit = new EditText(this); ipEdit.setText(ipConexao); alerta.setView(ipEdit); alerta.setMessage("Por favor, Confirme o endereço IP."); alerta.setPositiveButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { ipConexao = ipEdit.getText().toString(); Log.d(LOG_VOZ, "Nova Atribuição do Endreço IP: " + ipConexao); } }); alerta.create(); alerta.show(); } /** * Handle the click on the start recognition button. */ public void onClick(View v) { if (v.getId() == R.id.btn_speak) { //startVoiceRecognitionActivity(); Log.d(LOG_VOZ, "Iniciando a próxima tela"); Intent recordIntent = new Intent(this, GravacaoAtivity.class); Log.d(LOG_VOZ, "Iniciando a tela (instancia criada)"); startActivityForResult(recordIntent, INICIAR_GRAVACAO); Log.d(LOG_VOZ, "Gravação iniciada ..."); } } /** * Handle the results from the recognition activity. */ @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { Log.d(LOG_VOZ, "Iniciando onActivityResult()"); if (requestCode == INICIAR_GRAVACAO && resultCode == RESULT_OK) { String path = data.getStringExtra(GravacaoAtivity.RETORNO); conexaoSocket(path); } else Log.e(LOG_VOZ, "Resultado Inexperado ..."); } private void conexaoSocket(String path) { Socket socket = SocketOpener.openSocket(ipConexao, porta, tempoEspera); if(socket == null) return; try { DataOutputStream conexao = new DataOutputStream(socket.getOutputStream()); Log.d(LOG_VOZ, "Acessando arquivo ..."); File file = new File(path); DataInputStream arquivo = new DataInputStream(new FileInputStream(file)); Log.d(LOG_VOZ, "Iniciando Transmissão ..."); conexao.writeLong(file.length()); for(int i = 0; i < file.length(); i++) conexao.writeByte(arquivo.readByte()); Log.d(LOG_VOZ, "Transmissão realizada com sucesso..."); Log.d(LOG_VOZ, "Fechando a conexão..."); conexao.close(); socket.close(); Log.d(LOG_VOZ, "============ Processo finalizado com Sucesso =============="); } catch (IOException e) { Log.e(LOG_VOZ, "Erro ao fazer a conexão via Socket. " + e.getMessage()); // TODO Auto-generated catch block } } } class SocketOpener implements Runnable { private String host; private int porta; private Socket socket; public SocketOpener(String host, int porta) { this.host = host; this.porta = porta; socket = null; } public static Socket openSocket(String host, int porta, int timeOut) { SocketOpener opener = new SocketOpener(host, porta); Thread t = new Thread(opener); t.start(); try { t.join(timeOut); } catch(InterruptedException e) { Log.e(Reconhecimento.LOG_VOZ, "Erro ao fazer o join da thread do socket. " + e.getMessage()); //TODO: Mensagem informativa return null; } return opener.getSocket(); } public void run() { try { socket = new Socket(host, porta); }catch(IOException e) { Log.e(Reconhecimento.LOG_VOZ, "Erro na criação do socket. " + e.getMessage()); //TODO: Mensagem informativa } } public Socket getSocket() { return socket; } } Running on the desktop Java: import java.io.BufferedReader; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.net.ServerSocket; import java.net.Socket; public class ServidorArquivo { private static int porta = 5158; static String ARQUIVO = "voz.amr"; /** * Caminho que será gravado o arquivo de audio */ static String PATH = "/home/iade/Trabalho/lib/"; public static void main(String[] args) { int i = 1; try { System.out.println("Iniciando o Servidor Socket - Android."); ServerSocket s = new ServerSocket(porta); System.out.println("Servidor Iniciado com Sucesso..."); System.out.println("Aguardando conexões na porta: " + porta); while(true) { Socket recebendo = s.accept(); System.out.println("Aceitando conexão de nº " + i); new ThreadedHandler(recebendo).start(); i++; } } catch (Exception e) { System.out.println("Erro: " + e.getMessage()); e.printStackTrace(); } } } class ThreadedHandler extends Thread { private Socket socket; public ThreadedHandler(Socket so) { socket = so; } public void run() { DataInputStream entrada = null; DataOutputStream arquivo = null; try { entrada = new DataInputStream(socket.getInputStream()); System.out.println("========== Iniciando a leitura dos dados via Sockets =========="); long tamanho = entrada.readLong(); System.out.println("Tamanho do vetor " + tamanho); File file = new File(ServidorArquivo.PATH + ServidorArquivo.ARQUIVO); if(!file.exists()) file.createNewFile(); arquivo = new DataOutputStream(new FileOutputStream(file)); for(int j = 0; j < tamanho; j++) { arquivo.write(entrada.readByte()); } System.out.println("========== Dados recebidos com sucesso =========="); } catch (Exception e) { System.out.println("Erro ao tratar do socket: " + e.getMessage()); e.printStackTrace(); } finally { System.out.println("**** Fechando as conexões ****"); try { entrada.close(); socket.close(); arquivo.close(); } catch (IOException e) { System.out.println("Erro ao fechar conex&#65533;es " + e.getMessage()); e.printStackTrace(); } } System.out.println("============= Fim da Gravação ==========="); // tratar o arquivo String cmd1 = "ffmpeg -i voz.amr -ab 12288 -ar 16000 voz.wav"; String cmd2 = "soundstretch voz.wav voz2.wav -tempo=100"; String dir = "/home/iade/Trabalho/lib"; File workDir = new File(dir); File f1 = new File(dir+"/voz.wav"); File f2 = new File(dir+"/voz2.wav"); f1.delete(); f2.delete(); try { executeCommand(cmd1, workDir); System.out.println("realizou cmd1"); executeCommand(cmd2, workDir); System.out.println("realizou cmd2"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private void executeCommand(String cmd1, File workDir) throws IOException, InterruptedException { String s; Process p = Runtime.getRuntime().exec(cmd1,null,workDir); int i = p.waitFor(); if (i == 0) { BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream())); // read the output from the command while ((s = stdInput.readLine()) != null) { System.out.println(s); } } else { BufferedReader stdErr = new BufferedReader(new InputStreamReader(p.getErrorStream())); // read the output from the command while ((s = stdErr.readLine()) != null) { System.out.println(s); } } } } Thanks in advance.

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  • how to create trackballevent in android custom adapter?

    - by UMMA
    dear friends, i am using following code to create custom adapter for listview. now i want to use trackball click event in it but i dont know how to do that can any one help me out in creating ontracballevent in custom adapter? i have tried writing few lines but not able to solve it. public class EfficientAdapter extends BaseAdapter implements Filterable { private LayoutInflater mInflater; private Context context; int pos; public EfficientAdapter(Context context) { mInflater = LayoutInflater.from(context); this.context = context; } public View getView(final int position, View convertView, ViewGroup parent) { ViewHolder holder; convertView = mInflater.inflate(R.layout.adaptor_contentposts, null); convertView.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { //click functionality } }); MotionEvent event= MotionEvent.CREATOR.createFromParcel(null); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: //display click message } convertView.onTrackballEvent(event); return convertView; } class ViewHolder { TextView textLine; TextView textLine2; TextView PostedByAndPostedOn; ImageButton ImgButton; } @Override public Filter getFilter() { return null; } @Override public long getItemId(int position) { return 0; } @Override public int getCount() { return ad_id.length; } @Override public Object getItem(int position) { return ad_id[position]; } }

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  • Cast object to interface when created via reflection

    - by Al
    I'm trying some stuff out in Android and I'm stuck at when trying to cast a class in another .apk to my interface. I have the interface and various classes in other .apks that implement that interface. I find the other classes using PackageManager's query methods and use Application#createPackageContext() to get the classloader for that context. I then load the class, create a new instance and try to cast it to my interface, which I know it definitely implements. When I try to cast, it throws a class cast exception. I tried various things like loading the interface first, using Class#asSubclass, etc, none of which work. Class#getInterfaces() shows the interface is implemented. My code is below: PackageManager pm = getPackageManager(); List<ResolveInfo> lr = pm.queryIntentServices(new Intent("com.example.some.action"), 0); ArrayList<MyInterface> list = new ArrayList<MyInterface>(); for (ResolveInfo r : lr) { try { Context c = getApplication().createPackageContext(r.serviceInfo.packageName, Context.CONTEXT_IGNORE_SECURITY | Context.CONTEXT_INCLUDE_CODE); ClassLoader cl = c.getClassLoader(); String className = r.serviceInfo.name; if (className != null) { try { Class<?> cls = cl.loadClass(className); Object o = cls.newInstance(); if (o instanceof MyInterface) { //fails list.add((MyInterface) o); } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } // some exceptions removed for readability } } catch (NameNotFoundException e1) { e1.printStackTrace(); }

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  • can not override showDialog in Activity tab

    - by hornetbzz
    Trying to downgrade my appl from android 2.2 (API 8) down to android 2.1 (API7), I'm facing some issues with dialog boxes. Based on this thread, I'm trying to catch these exceptions but can't override the showDialog method. I turned the Java compiler from 1.5 to 1.6 according to this answer to a similar issue, but no changes, Eclipse still returns : Cannot override the final method from Activity public class MyActivity extends Activity implements SeekBar.OnSeekBarChangeListener { // ... some stuffs @Override // here is the issue public void showDialog(int dialogId) { try { super.showDialog(dialogId); } catch (IllegalArgumentException e) { Log.e(ACTIVITY_TAG, "Error dialog"); } } @Override protected Dialog onCreateDialog(int id) { switch (id) { case DIALOG_ALERT: // Create out AlertDialog Builder builder = new AlertDialog.Builder(this); builder.setMessage(msg); builder.setCancelable(false); builder.setPositiveButton(GOTO_BOOK, new OkOnClickListener()); builder.setNegativeButton(STAY_HERE, new CancelOnClickListener()); AlertDialog dialog = builder.create(); dialog.show(); break; case DIALOG_ONCREATE: // Create out AlertDialog during the "onCreate" method (only "Ok" // button) Builder builder2 = new AlertDialog.Builder(getParent()); builder2.setMessage(msg); builder2.setCancelable(false); builder2.setPositiveButton(GO_BACK, new OkOnClickListener()); AlertDialog dialog2 = builder2.create(); dialog2.show(); break; } return super.onCreateDialog(id); } // ... some stuffs }

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  • Dynamically adding controls from an Event after Page_Init

    - by GenericTypeTea
    Might seem like a daft title as you shouldn't add dynamic controls after Page_Init if you want to maintain ViewState, but I couldn't think of a better way of explaining the problem. I have a class similar to the following: public class WebCustomForm : WebControl, IScriptControl { internal CustomRender Content { get { object content = this.Page.Session[this.SESSION_CONTENT_TRACKER]; return content as CustomRender; } private set { this.Page.Session[this.SESSION_CONTENT_TRACKER] = value; } } } CustomRender is an abstract class that implements ITemplate that I use to self-contain a CustomForms module I'm in the middle of writing. On the Page_Init of the page that holds the WebCustomForm, I Initialise the control by passing the relevant Ids to it. Then on the overridden OnInit method of the WebCustomForm I call the Instantiate the CustomRender control that's currently active: if (this.Content != null) { this.Content.InstantiateIn(this); } The problem is that my CustomRender controls need the ability to change the CustomRender control of the WebCustomForm. But when the events that fire on the CustomRender fire, the Page_Init event has obviously already gone off. So, my question is, how can I change the content of the WebCustomForm from a dynamically added control within it? The way I see it, I have two options: I separate the CustomRender controls out into their own stand alone control and basically have an aspx page per control and handle the events myself on the page (although I was hoping to just make a control I drop on the page and forget about) I don't use events and just keep requesting the current page, but with different Request Parameters Or I go back to the drawing board with any better suggetions anyone can give me.

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  • jndi binding on jboss4.2.3 and ejb3

    - by broschb
    I am trying to deploy a stateless ejb on jboss 4.2.3 using ejb3 annotations. Everything builds and deploys correctly, and I do not get any errors when jboss starts up. However the ejb is not getting bound to any JNDI location for lookup when I look at the bindings in jboss. Below is what I have for my ejb. Remote @Remote public interface TestWebService { public String TestWebMethod(String param1, String param2); } Stateless EJB @Stateless @RemoteBinding(jndiBinding="TestWeb") @Remote(TestWebService.class) public class TestWebServiceBean implements TestWebService{ public String TestWebMethod(String param1, String param2) { System.out.println("HELLO "+param1+" "+param2); return "Welcome!!"; } } I have tried not having the @Remote and @RemoteBinding and it doesn't make a difference. I have also added and ejb-jar.xml file (which should not be needed with ejb3) and that does not appear to make a difference. Below is the output I see in the jboss log on startup. installing MBean: jboss.j2ee:ear=ejb_web_service_ear-0.0.1- SNAPSHOT.ear,jar=ejb_web_service-0.0.1-SNAPSHOT.jar,name=TestWebServiceBean,service=EJB3 with dependencies: 21:56:00,633 INFO [EJBContainer] STARTED EJB: com.tomax.ejb.TestWebServiceBean ejbName: TestWebServiceBean

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  • Tips on designing a .NET API for future use with F#

    - by Drew Noakes
    I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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  • Wicket: How to implement an IDataProvider/LoadableDetachableModel for indexed lists

    - by cretzel
    What's the best way to implement an IDataProvider and a LoadableDetachable in Wicket for an indexed list? Suppose I have a Customer who has a list of Adresses. class Customer { List adresses; } Now I want to implement a data provider/ldm for the adresses of a customer. I suppose the usual way is an IDataProvider as an inner class which refers to the customer model of the component, like: class AdressDataProvider implements IDataProvider { public Iterator iterator() { Customer c = (Customer)Component.this.getModel(); // somehow get the customer model return c.getAdresses().iterator(); } public IModel model(Object o) { Adress a = (Adress) o; // Return an LDM which loads the adress by id. return new AdressLoadableDetachableModel(a.getId()); } } Question: How would I implement this, when the adress does not have an ID (e.g. it's a Hibernate Embeddable/CollectionOfElements) but can only be identified by its index in the customer.adresses list? How do I keep reference to the owning entity and the index? In fact, I know a solution, but I wonder if there's a common pattern to do this.

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  • Creating futures using Apple's GCD

    - by jer
    I'm working on a library which implements the actor model on top of Grand Central Dispatch (specifically the C level API libdispatch). Basically a brief overview of my system is as such: Communication happens between actors using messages Multicast communication only (one actor to many actors) Senders and receivers are decoupled from one another using a blackboard where messages are pushed to. Messages are sent in the default queue asynchronously using dispatch_group_async() once a message gets pushed onto the blackboard. I'm trying to implement futures in the language right now, so I've created a new type which holds some information: A group of its own The value being 'returned' However, I have a problem since dispatch_block_t is of type void (^)(void) so it doesn't return anything. So my idea of in my future_new() function of setting up another group which can be used to execute a block returning a result, which I can store in my "value" member in my future_t structure, isn't going to work. The rest of the futures implementation is very clear, except it all depends on being able to get the value into the future back from the actor, acting on the message. When using the library, it would greatly reduce its usefulness if I had to ask users (and myself) to be aware when futures were going to be used by other parts of the system—It just isn't practical. I'm wondering if anyone can think of a way around this?

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • How to create TestContext for Spring Test?

    - by HDave
    Newcomer to Spring here, so pardon me if this is a stupid question. I have a relatively small Java library that implements a few dozen beans (no database or GUI). I have created a Spring Bean configuration file that other Java projects use to inject my beans into their stuff. I am now for the first time trying to use Spring Test to inject some of these beans into my junit test classes (rather than simply instantiating them). I am doing this partly to learn Spring Test and partly to force the tests to use the same bean configuration file I provide for others. In the Spring documentation is says I need to create an application context using the "TestContext" class that comes with Spring. I believe this should be done in a spring XML file that I reference via the @ContextConfiguration annotation on my test class. @ContextConfiguration({"/test-applicationContext.xml"}) However, there is no hint as to what to put in the file! When I go to run my tests from within Eclipse it errors out saying "failed to load Application Context"....of course.

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  • Is Stream.Write thread-safe?

    - by Mike Spross
    I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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  • hadoop implementing a generic list writable

    - by Guruprasad Venkatesh
    I am working on building a map reduce pipeline of jobs(with one MR job's output feeding to another as input). The values being passed around are fairly complex, in that there are lists of different types and hash maps with values as lists. Hadoop api does not seem to have a ListWritable. Am trying to write a generic one, but it seems i can't instantiate a generic type in my readFields implementation, unless i pass in the class type itself: public class ListWritable<T extends Writable> implements Writable { private List<T> list; private Class<T> clazz; public ListWritable(Class<T> clazz) { this.clazz = clazz; list = new ArrayList<T>(); } @Override public void write(DataOutput out) throws IOException { out.writeInt(list.size()); for (T element : list) { element.write(out); } } @Override public void readFields(DataInput in) throws IOException{ int count = in.readInt(); this.list = new ArrayList<T>(); for (int i = 0; i < count; i++) { try { T obj = clazz.newInstance(); obj.readFields(in); list.add(obj); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } } } } But hadoop requires all writables to have a no argument constructor to read the values back. Has anybody tried to do the same and solved this problem? TIA.

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  • Hibernate MapKeyManyToMany gives composite key where none exists

    - by larsrc
    I have a Hibernate (3.3.1) mapping of a map using a three-way join table: @Entity public class SiteConfiguration extends ConfigurationSet { @ManyToMany @MapKeyManyToMany(joinColumns=@JoinColumn(name="SiteTypeInstallationId")) @JoinTable( name="SiteConfig_InstConfig", joinColumns = @JoinColumn(name="SiteConfigId"), inverseJoinColumns = @JoinColumn(name="InstallationConfigId") ) Map<SiteTypeInstallation, InstallationConfiguration> installationConfigurations = new HashMap<SiteTypeInstallation, InstallationConfiguration>(); ... } The underlying table (in Oracle 11g) is: Name Null Type ------------------------------ -------- ---------- SITECONFIGID NOT NULL NUMBER(19) SITETYPEINSTALLATIONID NOT NULL NUMBER(19) INSTALLATIONCONFIGID NOT NULL NUMBER(19) The key entity used to have a three-column primary key in the database, but is now redefined as: @Entity public class SiteTypeInstallation implements IdResolvable { @Id @GeneratedValue(generator="SiteTypeInstallationSeq", strategy= GenerationType.SEQUENCE) @SequenceGenerator(name = "SiteTypeInstallationSeq", sequenceName = "SEQ_SiteTypeInstallation", allocationSize = 1) long id; @ManyToOne @JoinColumn(name="SiteTypeId") SiteType siteType; @ManyToOne @JoinColumn(name="InstalationRoleId") InstallationRole role; @ManyToOne @JoinColumn(name="InstallationTypeId") InstType type; ... } The table for this has a primary key 'Id' and foreign key constraints+indexes for each of the other columns: Name Null Type ------------------------------ -------- ---------- SITETYPEID NOT NULL NUMBER(19) INSTALLATIONROLEID NOT NULL NUMBER(19) INSTALLATIONTYPEID NOT NULL NUMBER(19) ID NOT NULL NUMBER(19) For some reason, Hibernate thinks the key of the map is composite, even though it isn't, and gives me this error: org.hibernate.MappingException: Foreign key (FK1A241BE195C69C8:SiteConfig_InstConfig [SiteTypeInstallationId])) must have same number of columns as the referenced primary key (SiteTypeInstallation [SiteTypeId,InstallationRoleId]) If I remove the annotations on installationConfigurations and make it transient, the error disappears. I am very confused why it thinks SiteTypeInstallation has a composite key at all when @Id is clearly defining a simple key, and doubly confused why it picks exactly just those two columns. Any idea why this happens? Is it possible that JBoss (5.0 EAP) + Hibernate somehow remembers a mistaken idea of the primary key across server restarts and code redeployments? Thanks in advance, -Lars

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  • Working with complex objects in Prevayler commands

    - by alexantd
    The demos included in the Prevayler distribution show how to pass in a couple strings (or something simple like that) into a command constructor in order to create or update an object. The problem is that I have an object called MyObject that has a lot of fields. If I had to pass all of them into the CreateMyObject command manually, it would be a pain. So an alternative I thought of is to pass my business object itself into the command, but to hang onto a clone of it (keeping in mind that I can't store the BO directly in the command). Of course after executing this command, I would need to make sure to dispose of the original copy that I passed in. public class CreateMyObject implements TransactionWithQuery { private MyObject object; public CreateMyObject(MyObject business_obj) { this.object = (MyObject) business_obj.clone(); } public Object executeAndQuery(...) throws Exception { ... } } The Prevayler wiki says: Transactions can't carry direct object references (pointers) to business objects. This has become known as the baptism problem because it's a common beginner pitfall. Direct object references don't work because once a transaction has been serialized to the journal and then deserialized for execution its object references no longer refer to the intended objects - - any objects they may have referred to at first will have been copied by the serialization process! Therefore, a transaction must carry some kind of string or numeric identifiers for any objects it wants to refer to, and it must look up the objects when it is executed. I think by cloning the passed-in object I will be getting around the "direct object pointer" problem, but I still don't know whether or not this is a good idea...

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  • How to access a variable in other class?

    - by Christine
    Hi! I've problem regarding GUI with one Menu and one Order Class. I've created a variable to store how many items have been selected in the Menu Class. private int totalSelected; The var totalSelected is live updated. It can be changed anytime depending on actionPerformed() function.(Exp: totalSelected will add up all the selected items) In the Order Class, how can I access to the live update variable totalSelected in order to retrieve the live update value? When I invoke getTotalSelected() function inside the Menu Class, I will only obtain a 0 value. Thanks for your help ^^! Please allow me to specify my question clearer. public class MenuTab extends JPanel { private JLabel display; private int totalSelected; public MenuTab() { .... } } public getTotalSelected(){ return totalSelected; } private class SelectedListener implements ActionListener { public void actionPerformed() { ....... //Assume that totalSelected has been updated! display = new JLabel("Total: " + totalSelected); // OK to display totalSelected live value here. } } // A new class is the confirmation of order public class OrderConfirmedTab extends JPanel{ private JLabel displayTotal; private MenuTab order = new MenuTab(); public OrderConfirmedTab() { ...... int totalSelected = order.getTotalSelected(); displayTotal = new JLabel("Total: " + totalSelected); // Problem to display totalSelected live value here. // Will obtain 0; // How can I obtain the live updated value from class MenuTab? Thanks! } }

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  • Building a control-flow graph from an AST with a visitor pattern using Java

    - by omegatai
    Hi guys, I'm trying to figure out how to implement my LEParserCfgVisitor class as to build a control-flow graph from an Abstract-Syntax-Tree already generated with JavaCC. I know there are tools that already exist, but I'm trying to do it in preparation for my Compilers final. I know I need to have a data structure that keeps the graph in memory, and I want to be able to keep attributes like IN, OUT, GEN, KILL in each node as to be able to do a control-flow analysis later on. My main problem is that I haven't figured out how to connect the different blocks together, as to have the right edge between each blocks depending on their nature: branch, loops, etc. In other words, I haven't found an explicit algorithm that could help me build my visitor. Here is my empty Visitor. You can see it works on basic langage expressions, like if, while and basic operations (+,-,x,^,...) public class LEParserCfgVisitor implements LEParserVisitor { public Object visit(SimpleNode node, Object data) { return data; } public Object visit(ASTProgram node, Object data) { data = node.childrenAccept(this, data); return data; } public Object visit(ASTBlock node, Object data) { } public Object visit(ASTStmt node, Object data) { } public Object visit(ASTAssignStmt node, Object data) { } public Object visit(ASTIOStmt node, Object data) { } public Object visit(ASTIfStmt node, Object data) { } public Object visit(ASTWhileStmt node, Object data) { } public Object visit(ASTExpr node, Object data) { } public Object visit(ASTAddExpr node, Object data) { } public Object visit(ASTFactExpr node, Object data) { } public Object visit(ASTMultExpr node, Object data) { } public Object visit(ASTPowerExpr node, Object data) { } public Object visit(ASTUnaryExpr node, Object data) { } public Object visit(ASTBasicExpr node, Object data) { } public Object visit(ASTFctExpr node, Object data) { } public Object visit(ASTRealValue node, Object data) { } public Object visit(ASTIntValue node, Object data) { } public Object visit(ASTIdentifier node, Object data) { } } Can anyone give me a hand? Thanks!

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  • Question about cloning in Java

    - by devoured elysium
    In Effective Java, the author states that: If a class implements Cloneable, Object's clone method returns a field-by-field copy of the object; otherwise it throws CloneNotSupportedException. What I'd like to know is what he means with field-by-field copy. Does it mean that if the class has X bytes in memory, it will just copy that piece of memory? If yes, then can I assume all value types of the original class will be copied to the new object? class Point { private int x; private int y; @Override public Point clone() { return (Point)super.clone(); } } If what Object.clone() does is a field by field copy of the Point class, I'd say that I wouldn't need to explicitly copy fields x and y, being that the code shown above will be more than enough to make a clone of the Point class. That is, the following bit of code is redundant: @Override public Point clone() { Point newObj = (Point)super.clone(); newObj.x = this.x; //redundant newObj.y = this.y; //redundant } Am I right? I know references of the cloned object will point automatically to where the original object's references pointed to, I'm just not sure what happens specifically with value types. If anyone could state clearly what Object.clone()'s algorithm specification is (in easy language) that'd be great. Thanks

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  • wcf class implementing multiple service contracts

    - by Archie
    Hello, I have a class TestService which implements two service contracts called IService1 and IService2. But I'm facing a difficulty in implementation. My Code looks as follows: Uri baseAddress = new Uri("http://localhost:8000/ServiceModel/Service"); Uri baseAddress1 = new Uri("http://localhost:8080/ServiceModel/Service1"); ServiceHost selfHost = new ServiceHost(typeof(TestService)); selfHost.AddServiceEndpoint(typeof(IService1), new WSHttpBinding(), baseAddress); selfHost.AddServiceEndpoint(typeof(IService2), new WSHttpBinding(), baseAddress1); ServiceMetadataBehavior smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; selfHost.Description.Behaviors.Add(smb); selfHost.Open(); Console.WriteLine("The service is ready."); Console.WriteLine("Press <ENTER> to terminate service."); Console.WriteLine(); Console.ReadLine(); selfHost.Close(); I'm getting a run time error as: The HttpGetEnabled property of ServiceMetadataBehavior is set to true and the HttpGetUrl property is a relative address, but there is no http base address. Either supply an http base address or set HttpGetUrl to an absolute address. What shall i do about it? Do I realy need two separate endpoints? Thanks.

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  • F# and statically checked union cases

    - by Johan Jonasson
    Soon me and my brother-in-arms Joel will release version 0.9 of Wing Beats. It's an internal DSL written in F#. With it you can generate XHTML. One of the sources of inspiration have been the XHTML.M module of the Ocsigen framework. I'm not used to the OCaml syntax, but I do understand XHTML.M somehow statically check if attributes and children of an element are of valid types. We have not been able to statically check the same thing in F#, and now I wonder if someone have any idea of how to do it? My first naive approach was to represent each element type in XHTML as a union case. But unfortunately you cannot statically restrict which cases are valid as parameter values, as in XHTML.M. Then I tried to use interfaces (each element type implements an interface for each valid parent) and type constraints, but I didn't manage to make it work without the use of explicit casting in a way that made the solution cumbersome to use. And it didn't feel like an elegant solution anyway. Today I've been looking at Code Contracts, but it seems to be incompatible with F# Interactive. When I hit alt + enter it freezes. Just to make my question clearer. Here is a super simple artificial example of the same problem: type Letter = | Vowel of string | Consonant of string let writeVowel = function | Vowel str -> sprintf "%s is a vowel" str I want writeVowel to only accept Vowels statically, and not as above, check it at runtime. How can we accomplish this? Does anyone have any idea? There must be a clever way of doing it. If not with union cases, maybe with interfaces? I've struggled with this, but am trapped in the box and can't think outside of it.

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  • Refreshing Read-Only (Chained) Property in MVVM

    - by Wonko the Sane
    I'm thinking this should be easy, but I can't seem to figure this out. Take these properties from an example ViewModel (ObservableViewModel implements INotifyPropertyChanged): class NameViewModel : ObservableViewModel { Boolean mShowFullName = false; string mFirstName = "Wonko"; string mLastName = "DeSane"; private readonly DelegateCommand mToggleName; public NameViewModel() { mToggleName = new DelegateCommand(() => ShowFullName = !mShowFullName); } public ICommand ToggleNameCommand { get { return mToggleName; } } public Boolean ShowFullName { get { return mShowFullName; } set { SetPropertyValue("ShowFullName", ref mShowFullName, value); } } public string Name { get { return (mShowFullName ? this.FullName : this.Initials); } } public string FullName { get { return mFirstName + " " + mLastName; } } public string Initials { get { return mFirstName.Substring(0, 1) + "." + mLastName.Substring(0, 1) + "."; } } } The guts of such a [insert your adjective here] View using this ViewModel might look like: <TextBlock x:Name="txtName" Grid.Row="0" Text="{Binding Name}" /> <Button x:Name="btnToggleName" Command="{Binding ToggleNameCommand}" Content="Toggle Name" Grid.Row="1" /> The problem I am seeing is when the ToggleNameCommand is fired. The ShowFullName property is properly updated by the command, but the Name binding is never updated in the View. What am I missing? How can I force the binding to update? Do I need to implement the Name properties as DependencyProperties (and therefore derive from DependencyObject)? Seems a little heavyweight to me, and I'm hoping for a simpler solution. Thanks, wTs

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  • How to fix IllegalStateException error when trying to update a listview?

    - by Michael Vetrano
    Hi guys, I am trying to get this code to run, but I get an IllegalStateException when I run this code saying that the content of the listview wasn't notified, yet I have a notification upon updating the data. This is a custom listview adapter. Here is the relevant part of my code: class LoadingThread extends Thread { public void run() { int itemsOriginallyLoaded = 0; synchronized( items ) { itemsOriginallyLoaded = items.size(); } for( int i = itemsOriginallyLoaded ; i < itemsToLoad ; ++i ) { Log.d( LOG_TAG, "Loading item #"+i ); //String item = "FAIL"; //try { String item = "FAIL"; try { item = stockGrabber.getStockString(dataSource.get(i)); } catch (ApiException e) { Log.e(LOG_TAG, "Problem making API request", e); } catch (ParseException e) { Log.e(LOG_TAG, "Problem parsing API request", e); } //} catch (ApiException e) { // Log.e(TAG, "Problem making API request", e); //} catch (ParseException e) { // Log.e(TAG, "Problem parsing API request", e); //} synchronized( items ) { items.add( item ); } itemsLoaded = i+1; uiHandler.post( updateTask ); Log.d( LOG_TAG, "Published item #"+i ); } if( itemsLoaded >= ( dataSource.size() - 1 ) ) allItemsLoaded = true; synchronized( loading ) { loading = Boolean.FALSE; } } } class UIUpdateTask implements Runnable { public void run() { Log.d( LOG_TAG, "Publishing progress" ); notifyDataSetChanged(); } }

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