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  • What to do when ServerSocket throws IOException and keeping server running

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating. EDIT: After some answers, here my attempt to deal with the IOException. Would the implementation be guaranteeing keeping the server up and only re-create server socket when only necessary? while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... bindExceptionCounter = 0; } catch (IOException e) { e.printStackTrace(); recreateServerSocket(); } } private void recreateServerSocket() { while (keepRunning) { try { logger.info("Try to re-create Server Socket"); ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(RateTableServer.RATE_EVENT_SERVER_PORT); // No exception thrown, then use the new socket. serverSocket = socket; break; } catch (BindException e) { logger.info("BindException indicates that the server socket is still good.", e); bindExceptionCounter++; if (bindExceptionCounter < 5) { break; } } catch (IOException e) { logger.warn("Problem to re-create Server Socket", e); e.printStackTrace(); try { Thread.sleep(30000); } catch (InterruptedException ie) { logger.warn(ie); } } } }

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  • Junit exception test

    - by Prithis
    I have two tests to check the expected exception throw. I am using Junit 4 and has following syntax. @Test(expected=IllegalArgumentException.class) public void testSomething(){ .......... } One of the tests fail even though IllegalArgumentException is thrown and the other passes. Any idea whats missing?? I modified the test which is failing to following and it passes. public void testSomething(){ try{ ............ //line that throws exception fail(); }catch(IllegalArgumentException e) { } }

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  • Getting the instance when Constructor#newInstance throws?

    - by Shtééf
    I'm working on a simple plugin system, where third party plugins implement a Plugin interface. A directory of JARs is scanned, and the implementing classes are instantiated with Constructor#newInstance. The thing is, these plugins call back into register* methods of the plugin host. These registrations use the Plugin instance as a handle. My problem is how to clean up these registrations if the constructor decides to fail and throw halfway through. InvocationTargetException doesn't seem to have anything on it to get the instance. Is there a way to get at the instance of an exception throwing constructor? P.S.: It's typically strongly advised to users that the constructor not do anything, but in practice people are doing it any ways.

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  • How to set and get the id for the items in the spinner in Android

    - by Haresh Chaudhary
    I have a problem in my project that i am displaying a activity which would contain the details of the project which is previously added in Project Management System.. Now the fields in it are like: Fields of the Activity Name Of Project: ABC(EditText) Name Of Developer : ________(Spinner) Deadline : ________(Date Picker) Created On : _______(TextView) . . Now, the Spinner contains the Names of all developers working in the Company..I have used the ArrayAdapter with a array having the names of all the developers which is fetched from the database.. The problem is that when i update the Name Of Developer field, i get Only the Name of the Developer which is not enough to update the data as their can be multiple developers with the same name in the Company..So now I require the id of the developers to update it.. How to store that id of the developers with the Spinner so that i can achieve this.. Please help me to sort this out. Actually what i want to do like is as that we do in html:: <select> <option id="1">Developer1</option> <option id="2">Developer2</option> <option id="3">Developer2</option> <option id="4">Developer2</option> </select> where the id attached would be the database id....I want to imitate this in our android.... This the code that i have used to store the names in the array:: String alldevelopers = null; try { ArrayList<NameValuePair> postP = new ArrayList<NameValuePair>(); alldevelopers = CustomHttpClient.executeHttpPost( "/fetchdevelopers.php", postP); String respcl = alldevelopers.toString(); alldevelopersParser dev = new alldevelopersParser(); ow = dev.parseByDOM(respcl); } catch (Exception e) { e.printStackTrace(); } String developers[] = new String[ow.length]; //dev is a class object for (int n = 0; n < ow.length; n++) { developers[n] = ow.developer[n][2]; } This is the Spinner that would spin the array.. final Spinner devl = (Spinner) findViewById(R.id.towner); devl.setOnItemSelectedListener(managetasks.this); ArrayAdapter<String> b = new ArrayAdapter<String>getApplicationContext(), android.R.layout.simple_spinner_item,developers); b.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line); devl.setAdapter(b);

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  • When do instance variables get initialized and values assigned?

    - by AKh
    When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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  • Help in debugging the string concatenation code

    - by mithun1538
    I have a code to concatenate strings. However, for some reason, the final string is not a combination of the required strings. Consider the following code : //cusEmail is of type String[] String toList = ""; for(i=0; i < cusEmail.length - 1; i++) { toList.concat(cusEmail[i]); toList.concat("; "); System.out.println(cusEmail[i]); } toList.concat(cusEmail[i]); System.out.println(toList); The first sout statement displays the strings in cusEmail[i] correctly. However, once concatenated, the second sout displays a blank / empty. Any reason for this? Am i concatenating it correctly?

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  • JTextPane insert component, faulty vertical alignment

    - by John O
    I have a JTextPane, into which I need to insert a JComponent. I'm using JTextPane.insertComponent(Component). The item is indeed inserted, but the vertical positioning is too high. Instead of having the bottom of the component aligned with the baseline of the current line of text, the component is way above that position, blocking out/over-painting lines of text appearing above. I have tried calling setAlignmentY(float) with various values, on both the inserted component and the JTextPane, but it doesn't affect the behavior at all. My guess: there seems to be some state inside my JTextPane or its Document that I need to be changing. But I don't know what it is. John

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  • Cab't run a web application with GWText

    - by Anto
    I am using the GWT and the GWTExt libraries with Eclipse for the first time. I have followed all the procedures but when I go run the web application the following error appears: 1) In the Problems tab, I have this message: Description Resource Path Location Type The following classpath entry 'C:\Documents and Settings\CiuffreA\Desktop\GWTExt\gwtext-2.0.5\gwtext.jar' will not be available on the server's classpath GWTProject Unknown Google Web App Problem 2) In the Development Mode tab, the following 2 messages appears: 23:41:25.906 [ERROR] [mockupproject] Unable to load module entry point class com.example.myproject.client.MockUpProject Failed to load module 'mockupproject' from user agent 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1042 Safari/532.5' at localhost:3853 If anyone has a clue about where the problem may be, please give me a hint...

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  • Example of standalone Apache Qpid (amqp) Junit Test

    - by Wiretap
    Does anyone have an example of using Apache Qpid within a standalone junit test. Ideally I want to be able to create a queue on the fly which I can put/get msgs within my test. So I'm not testing QPid within my test, I'll use integration tests for that, however be very useful to test methods handling msgs with having to mock out a load of services.

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  • DB2 Driver Connection Hanging in Glassfish Connection Pool

    - by Ant
    We have an intermittent issue around the DB2 used from a Glassfish connection pool. What happens is this: Under situations where the database (DB2 on ZOS) is under stress, our application (which is a multi-threaded application using connections to DB2 via a Glassfish connection pool) stops doing anything. The following are observed: 1) Looking at the server using JConsole, we can see a thread waiting indefinitely in the DB2 driver's getConnection() method. We can also see that it has gained a lock on a Vector within the driver. Several other threads are also calling the getConnection() method in the driver, and are hanging waiting for the lock on the Vector to be released. 2) Looking at the database itself, we can see that there are connections from the Glassfish server open and waiting to be used. It seems that there is some sort of mismatch between the connection pool on Glassfish and the connections actually open to DB2. Has anyone come across this issue before? Or something similar? If you need any more information that I haven't provided, then please let me know!

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  • Call the method of base Class which was over ridden

    - by Abhijith Venkata
    I have illustrated my question in this example class Car { public void start(){ System.out.println("Car Started!!!"); } } class Mercedes extends Car { public void start(){ System.out.println("Mercedes Started!!!"); } } Now, in my main program, I write Mercedes m = new Mercedes(); m.start(); It prints: Mercedes Started!!! How do I call the start() method of Car class using the same object so that the output can be Car Started!!!. Edit: Actually It was asked in an interview I attended. I gave the super keyword answer. But the interviewer denied it. He said he'd give me a hint and said Virtual Function. I have no idea how to use that hint.

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  • JPanel: both implementing my own paintComponent() and rendering children doesn't work

    - by Paul Marshall
    I'm extending a JPanel to display a game board, and adding a JEditorPane at the bottom to hold some status text. Unfortunately, the game board renders just fine, but the JEditorPane is just a blank gray area until I highlight the text in it, when it will render whatever text is highlighted (but not the rest). If I'm understanding Swing right, it should work, because super.paintComponent(g) should render the other children (i.e., the JEditorPane). Tell me, o great stackoverflow, what bonehead mistake am I making? public GameMap extends JPanel { public GameMap() { JEditorPane statusLines = new JEditorPane("text/plain","Stuff"); this.setLayout(new BoxLayout(this,BoxLayout.PAGE_AXIS)); this.add(new Box.Filler(/*enough room to draw my game board*/)); this.add(statusLines); } public void paintComponent(Graphics g){ super.paintComponent(g); for ( all rows ){ for (all columns){ //paint one tile } } } }

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  • Vector ArrayIndexOutOfBounds

    - by Esmond
    I'm having an ArrayIndexOutofBounds exception with the following code. The exception is thrown at the line where Node nodeJ = vect.get(j) but it does not make sense to me since j is definitely smaller than i and Node nodeI = vect.get(i) does not throw any exception. any help is appreciated. public static Vector join(Vector vect) throws ItemNotFoundException { Vector<Node> remain = vect; for (int i = 1; i < vect.size(); i++) { Node nodeI = vect.get(i); for (int j = 0; j < i; j++) {//traverse the nodes before nodeI Node nodeJ = vect.get(j); if (nodeI.getChild1().getSeq().equals(nodeJ.getSeq())) { nodeI.removeChild(nodeJ); nodeI.setChild(nodeJ); remain.remove(j); } if (nodeI.getChild2().getSeq().equals(nodeJ.getSeq())) { nodeI.removeChild(nodeJ); nodeI.setChild(nodeJ); remain.remove(j); } } } return remain; }

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  • JMF. Create new custom streamdatasource

    - by Afro Genius
    Hi there. I am looking to create a means of building a DataSource object (and hence a Processor) that gets data from a stream instead of a file, RTP, and so on. I am writing a module for a much larger application that is meant to transparently transcode audio data. Going through the JMF docs only specify how to create a source from file however I need to be able to create a source from a stream within my application. Any idea where I can start looking?

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  • Handle Transaction on differents EARs

    - by rfders
    Hello, what is the best practice to handle multiple EARs and the same transaction, as far as we know we need to apply XA concepts in order transaction works correctly. but apparently in currents project that we've been working on, this is not strictly necessary for creates and updates; however if we try to retrieve any collection from an entity we get an error that say there its not an active transaction or it was closed, but if we update Entity A in Ear A and update Entity B in Ear B it works perfectly when Entity A and Entity B has different datasources, at this point we are so confused about that, because we haven't configure any xa datasource yet. how is the best approach to work with this. transaction are handles by beans and not by the container and datasource are different between EAR A and EAR B

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  • Scaling an Image in GWT

    - by Daniel
    Changing the size of an Image Widget in GWT changes the size of the image element, but does not rescale the image on the screen. Therefore, the following will not work: Image image = new Image(myImageResource); image.setHeight(newHeight); image.setWidth(newWidth); image.setPixelSize(newWidth, newHeight); This is because GWT implements its Image widget by setting the background-image of the HTML <img... /> element as the image, using CSS. How does one get the actual image to resize?

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  • Efficient representation of Hierarchies in Hibernate.

    - by Alison G
    I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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  • Lost with hibernate - OneToMany resulting in the one being pulled back many times..

    - by Andy
    I have this DB design: CREATE TABLE report ( ID MEDIUMINT PRIMARY KEY NOT NULL AUTO_INCREMENT, user MEDIUMINT NOT NULL, created TIMESTAMP NOT NULL, state INT NOT NULL, FOREIGN KEY (user) REFERENCES user(ID) ON UPDATE CASCADE ON DELETE CASCADE ); CREATE TABLE reportProperties ( ID MEDIUMINT NOT NULL, k VARCHAR(128) NOT NULL, v TEXT NOT NULL, PRIMARY KEY( ID, k ), FOREIGN KEY (ID) REFERENCES report(ID) ON UPDATE CASCADE ON DELETE CASCADE ); and this Hibernate Markup: @Table(name="report") @Entity(name="ReportEntity") public class ReportEntity extends Report{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name="ID") private Integer ID; @Column(name="user") private Integer user; @Column(name="created") private Timestamp created; @Column(name="state") private Integer state = ReportState.RUNNING.getLevel(); @OneToMany(mappedBy="pk.ID", fetch=FetchType.EAGER) @JoinColumns( @JoinColumn(name="ID", referencedColumnName="ID") ) @MapKey(name="pk.key") private Map<String, ReportPropertyEntity> reportProperties = new HashMap<String, ReportPropertyEntity>(); } and @Table(name="reportProperties") @Entity(name="ReportPropertyEntity") public class ReportPropertyEntity extends ReportProperty{ @Embeddable public static class ReportPropertyEntityPk implements Serializable{ /** * long#serialVersionUID */ private static final long serialVersionUID = 2545373078182672152L; @Column(name="ID") protected int ID; @Column(name="k") protected String key; } @EmbeddedId protected ReportPropertyEntityPk pk = new ReportPropertyEntityPk(); @Column(name="v") protected String value; } And i have inserted on Report and 4 Properties for that report. Now when i execute this: this.findByCriteria( Order.asc("created"), Restrictions.eq("user", user.getObject(UserField.ID)) ) ); I get back the report 4 times, instead of just the once with a Map with the 4 properties in. I'm not great at Hibernate to be honest, prefer straight SQL but I must learn, but i can't see what it is that is wrong.....? Any suggestions?

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  • readObject() vs. readResolve() to restore transient fields

    - by Joonas Pulakka
    According to Serializable javadoc, readResolve() is intended for replacing an object read from the stream. But is it OK to use it for restoring transient fields, like so: private Object readResolve() { transientField = something; return this; } as opposed to using readObject(): private void readObject(ObjectInputStream s) { s.defaultReadObject(); transientField = something; } Is there any reason to choose one over other, when used to just restore transient fields?

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  • Magi squares, recursive

    - by user310827
    Hi, my problem is, I'm trying to permute all posibilities for 3x3 square and check if the combination is magic. I've added a tweak with (n%3==0) if statement that if the sum of numbers in row differs from 15 it breaks the creation of other two lines... but it doesn't work, any suggestions, I call the function with Permute(1). public static class Global { //int[] j = new int[6]; public static int[] a= {0,0,0,0,0,0,0,0,0}; public static int[] b= {0,0,0,0,0,0,0,0,0}; public static int count = 0; } public static void Permute(int n) { int tmp=n-1; for (int i=0;i<9;i++){ if (Global.b[i]==0 ) { Global.b[i]=1; Global.a[n-1]=i+1; if ((n % 3) == 0) { if (Global.a[0+tmp]+Global.a[1+tmp]+Global.a[2+tmp] == 15) { if (n<9) { Permute(n+1); } else { isMagic(Global.a); } } else break; } else { Permute(n+1); } Global.b[i]=0; } } }

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  • Accessing FacesContext from Web Service

    - by scriptmonster
    I'm developing a Web Service which will be called by clients which are written by me. In the web service I need to use application-wide objects which eases the load of application on the system. I have implemented my application-wide objects as shown in this question. I can use my object in a jsf page with no problem as follows. MyObject mo = (MyObject) FacesContext.getCurrentInstance().getExternalContext().getApplicationMap().get("MyObjectsName"); But when it comes to use it in a Web Service Request FacesContext.getCurrentInstance() returns null. Is there any way to use the FacesContext in a web service.

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