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  • How to maintain a pool of names ?

    - by Jacques René Mesrine
    I need to maintain a list of userids (proxy accounts) which will be dished out to multithreaded clients. Basically the clients will use the userids to perform actions; but for this question, it is not important what these actions are. When a client gets hold of a userid, it is not available to other clients until the action is completed. I'm trying to think of a concurrent data structure to maintain this pool of userids. Any ideas ? Would a ConcurrentQueue do the job ? Clients will dequeue a userid, and add back the userid when they are finished with it.

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  • Spring bean initialization in a web app

    - by EugeneP
    We work with a web application and autowire beans using WebApplicationContextUtils in the init method. Could you clarify some details about bean initialization? The question rises from the static factory method. Suppose there's a bean that is created in a static factory method. As we can see, when the web app is deployed, the ContextLoaderListener initializes all the beans present in Spring xml config file. Now happens such a thing. In the static factory method we run a timer that starts ticking. But in reality we wouldn't want it to start ticking unless the bean is injected into a property of the object ! That is question number one - all the beans are automatically initialized on deploy - correct? And after that when we need an injection, it simply feels the link with the address of the object created during initialization, though OBJECT WAS CREATED ON WEB APP DEPLOY, immediately ! (I assume the default singleton-creation Spring behavior) Second question: are all copies of a web app use the same beans, so all beans are WEB-APP wide, every Spring bean is shared between all the copies of this web app running?

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  • Defining tokens at runtime

    - by Peter Crenshaw
    I want to write a parser for EDIFACT messages with JavaCC. My problem is that I cannot define all terminal symbols before parsing a message because at the begining of each message there is a so called "Advice Segment" ("UNA" Segment) which defines things like element seperator symbol, escape symbol, segment terminator symbol and decimal notation (e.g. '.' or ','). So I think/guess the production rules need some kind of variables which must be set at runtime during parsing. Can this be done with JavaCC and if so how? Or is there another way I am missing?

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  • How to use locks/synchronization here

    - by MasterGberry
    I have this code block here and i need to make sure the rankedPlayersWaitingForMatch is synchronized between threads properly. I was going to use synchronize but that i don't think will work here because of the variable being used in the if statement. I read online about final Lock lock = new ReentrantLock(); but I am a bit confused on how to use it in this case properly with the try/finally block. Can I get a quick example? Thanks // start synchronization if (rankedPlayersWaitingForMatch.get(rankedType).size() >= 2) { Player player1 = rankedPlayersWaitingForMatch.get(rankedType).remove(); Player player2 = rankedPlayersWaitingForMatch.get(rankedType).remove(); // end synchronization // ... I don't want this all to be synchronized, just after the first 2 remove() } else { // end synchronization // ... }

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  • Using JSF, JPA and DAO. Without Spring?

    - by ich-bin-drin
    Hi, till now i still worked with JSF and JPA without DAOs. Now i'd like to use DAOs. But how can i initialize the EntityManager in the DAO-Classes? public class AdresseHome { @PersistenceContext private EntityManager entityManager; public void persist(Adresse transientInstance) { log.debug("persisting Adresse instance"); try { entityManager.persist(transientInstance); log.debug("persist successful"); } catch (RuntimeException re) { log.error("persist failed", re); throw re; } } } Have I to use Spring or is there a solution that works without Spring? Thanks.

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  • In this example, would Customer or AccountInfo properly be the entity group parent?

    - by Badhu Seral
    In this example, the Google App Engine documentation makes the Customer the entity group parent of the AccountInfo entity. Wouldn't AccountInfo encapsulate Customer rather than the other way around? Normally I would think of an AccountInfo class as including all of the information about the Customer. import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.appengine.api.datastore.Key; import com.google.appengine.api.datastore.KeyFactory; @PersistenceCapable public class AccountInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; public void setKey(Key key) { this.key = key; } } // ... KeyFactory.Builder keyBuilder = new KeyFactory.Builder(Customer.class.getSimpleName(), "custid985135"); keyBuilder.addChild(AccountInfo.class.getSimpleName(), "acctidX142516"); Key key = keyBuilder.getKey(); AccountInfo acct = new AccountInfo(); acct.setKey(key); pm.makePersistent(acct);

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  • Should I create protected constructor for my singleton classes?

    - by Vijay Shanker
    By design, in Singleton pattern the constructor should be marked private and provide a creational method retuning the private static member of the same type instance. I have created my singleton classes like this only. public class SingletonPattern {// singleton class private static SingletonPattern pattern = new SingletonPattern(); private SingletonPattern() { } public static SingletonPattern getInstance() { return pattern; } } Now, I have got to extend a singleton class to add new behaviors. But the private constructor is not letting be define the child class. I was thinking to change the default constructor to protected constructor for the singleton base class. What can be problems, if I define my constructors to be protected? Looking for expert views....

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  • Scanner cuts off my String after about 2400 characters

    - by Ventrue
    I've got some very basic code like while (scan.hasNextLine()) { String temp = scan.nextLine(); System.out.println(temp); } where scan is a Scanner over a file. However, on one particular line, which is about 6k chars long, temp cuts out after something like 2470 characters. There's nothing special about when it cuts out; it's in the middle of the word "Australia." If I delete characters from the line, the place where it cuts out changes; e.g. if I delete characters 0-100 in the file then Scanner will get what was previously 100-2570. I've used Scanner for larger strings before. Any idea what could be going wrong?

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  • How to keep the popup menu of a JComboBox open on populating it ?

    - by Stormshadow
    I have a JComboBox on my Panel. One of the popup menu items is 'More' and when I click that I fetch more menu items and add them to the existing list. After this, I wish to keep the popup menu open so that the user realizes that more items have been fetched however, the popup closes. The event handler code I am using is as follows public void actionPerformed(ActionEvent e) { if (e.getSource() == myCombo) { JComboBox selectedBox = (JComboBox) e.getSource(); String item = (String) selectedBox.getSelectedItem(); if (item.toLowerCase().equals("more")) { fetchItems(selectedBox); } selectedBox.showPopup(); selectedBox.setPopupVisible(true); } } private void fetchItems(JComboBox box) { box.removeAllItems(); /* code to fetch items and store them in the Set<String> items */ for (String s : items) { box.addItem(s); } } I do not understand why the showPopup() and setPopupVisible() methods are not functioning as expected.

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  • Tomcat Postgres Connection

    - by user191207
    Hi, I'm using a singleton class for a PostgresSQL connection inside a servelet. The problem is that once it is open it works for a while (I guess until some timeout), and then it starts throwing a I/O exception. Any idea what is happening to the singleton class inside Tomcat VM? Thanks

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  • How to schedule an alarm so that the intent is broadcast everytime the date changes?

    - by rogerstone
    I want to schedule an alarm which throws an intent when the date changes. I know that this would do this the job alarms.setRepeating(AlarmManager.RTC_WAKEUP,triggerAtTime, interval,alarmIntent); But what is confusing me is what to put in the triggerAtTime and the interval.It says System.currentTimeMillis() timebase. I might be installing the app on any day so the TriggerAtTime should be midnight of that day and the interval would be 24 hours from there on. How can I acheive this.Can someone tell me what to put in TriggerAtTime and interval in the required format. Thanks

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  • Add a listener inside or outside get method

    - by James P.
    I'm learning Swing and have composed an interface using a series of get methods to add components. Is it a good practise to add a Listener inside a get method as follows? I'd like to make things as decoupled as possible. private JButton getConnectButton() { if (connectButton == null) { connectButton = new JButton(); connectButton.setText("Connect"); connectButton.setSize(new Dimension(81, 16)); connectButton.setLocation(new Point(410, 5)); connectButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // actionPerformed code goes here } }); } return connectButton; }

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  • Image Uploading in a web aplication.

    - by sandeep manglani
    actually i m devloping a web application that provides facility to users upload the image as we see in orkut and facebook through a form and a upload button.but the actually problem I am facing is : 1.should i store the image in database using Large data objects ie BLOB and the problem arises of retrieving it back from the database and then displaying it on the form. 2.sholud i store the absolute path of the the image in database and provide it to the source tag of the image in the html form.

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  • Spring MVC - JSP - Place to Store Environment Specific Constants

    - by jboyd
    Where in the Spring-MVC/JSP application would you store things that need to be accessed by both the controllers and views such as environment specific base_url's, application ids to be used in javascript and so on? I've tried creating an application scoped bean and then at the top of my JSPs, but that doesn't seem to be working. <!-- Environment --> <bean id="myEnv" class="com.myapp.MyAppEnvironment" scope="application"> <property name="baseUrl" value="http://localhost:8080/myapp/"/> <property name="videoPlayerId" value="234346565"/> </bean> And using it in the following manner <jsp:useBean id="myEnv" scope="application" type="com.myapp.MyAppEnvironment"/>

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  • Advantages of using a Dynamic Client with JAX-WS

    - by jconlin
    What are the advantages of using a dynamic client with JAX-WS services as opposed to just using generated client classes? What are the disadvantages? **For my particular case I am using Apache CXF, I'm not sure what other libraries allow "dynamic" clients. -I thought I didn't need to add this, but... I'm looking for non-obvious(I know...subjective) advantages. I don't need someone else to tell me that an advantage of not using generated classes is that I don't need to generate classes.

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  • Problem at JUnit test with generics

    - by Tom Brito
    In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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  • Is it against best practice to throw Exception on most JUnit tests?

    - by Chris Knight
    Almost all of my JUnit tests are written with the following signature: public void testSomething() throws Exception My reasoning is that I can focus on what I'm testing rather than exception handling which JUnit appears to give me for free. But am I missing anything by doing this? Is it against best practice? Would I gain anything by explicitly catching specific exceptions in my test and then fail()'ing on them?

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  • JAXB Marshalling supply name space for root element dynamically

    - by Venkat
    I have to pass the namespace for root element dynamically while marshalling using jaxb (JAXB 2.1.10 - JDK 6). i will be using the genrated xml to call different webservices which is qualified with different namespaces but same input xml. here is my sample jaxb annotated class .....guide me with your valuable inputs. @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "", propOrder = { "taskName", "taskType" }) @XmlRootElement(name = "TaskRequest") public class TaskRequest { @XmlElement(name = "TaskName", required = true) protected String taskName; @XmlElement(name = "TaskType", required = true) protected String taskType; public String getTaskName() { return taskName; } public void setTaskName(String value) { this.taskName = value; } public String getTaskType() { return taskType; } public void setTaskType(String value) { this.taskType = value; } }

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