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  • How to copy generically superclass instances to subclass instances?

    - by gerry
    Hi @all, I have a class hierarchy / inheritance like this: public class A { private String name; // with getters & setters public void doAWithName(){ ... } } public class B extends A { public void doBWithName(){ // a differnt implementation to what I do in class A } } public class C extends B { public void doCWithName(){ // a differnt implementation to what I do in class A and B } } So at one time there is a instance of class A with the initialized field "name". Later I want this instance of A get wrapped into instance of B or C. So the superclasses should be get wrapped with a subclass! How can I make this most efficent with respect to DRY? I've thought about a constructor that does some copying with the getters/setters. But in this case I have to repeat myself - and this doesn't respect anymore to my initial requirement of DRY! So, how can I warp A to B by just initializing B's new fields (with default values) and delegating the rest to a method in A (which knows more than B about which fields of A should be accessed...). In the same way: If A should be wrapped into C only a method in c should init C's 'new' fields, delegate to B's wrap method (which therefore inits B's 'new' fields in C) and at last B delegates to A which copies it's fields to the fields of C). So in the end I have a new instance of C which has the values of A wrapped (and some default init values to the fields which the inheritance hierarchy has added).

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  • Hibernate/JPA - annotating bean methods vs fields

    - by Benju
    I have a simple question about usage of Hibernate. I keep seeing people using JPA annotations in one of two ways by annotating the fields of a class and also by annotating the get method on the corresponding beans. My question is as follows: Is there a difference between annotating fields and bean methods with JPA annoations such as @Id. example: @Entity public class User { **@ID** private int id; public int getId(){ return this.id; } public void setId(int id){ this.id=id; } } -----------OR----------- @Entity public class User { private int id; **@ID** public int getId(){ return this.id; } public void setId(int id){ this.id=id; } }

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  • Discover NullPointerException bugs using FindBug

    - by alex2k8
    When I run FindBug on this code, it reports NO issues. boolean _closed = false; public void m1(@Nullable String text) { if(_closed) return; System.out.println(text.toLowerCase()); } While here it finds issue as expected: public void m1(@Nullable String text) { System.out.println(text.toLowerCase()); // FireBug: text must be nonnull but is marked as nullable } Why does it fail in first case?

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  • No Hibernate Exception on the same insert of data

    - by Mark Estrada
    Hi All, Hibernate Newbie here. I am quite unsure why I am not getting any exception when I am executing below code. On first attempt, this code creates the Book Entry on my Book Table. But my concern is that when I execute below code again, no error was pop out by Hibernate. I was in fact expecting some sort of Violation of Primary Key Constraints as what I have bee doing in JDBC code. public class BookDao { public void createBook(Book bookObj) { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); session.beginTransaction(); session.saveOrUpdate(bookObj); session.getTransaction().commit(); } } public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { // Create the SessionFactory from hibernate.cfg.xml return new AnnotationConfiguration().configure() .buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed ex.printStackTrace(); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } } public class BookDBStarter { public static void main(String[] args) { Book bookHF = new Book(); bookHF.setIsbn("HF-12345"); bookHF.setName("Head First HTML"); bookHF.setPublishDate(new Date()); BookDao daoBook = new BookDao(); daoBook.createBook(bookHF); } } Is this normal hibernate way? And how will I know if my insert is successful? Any thoughts?

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  • Why are static imports of static methods with same names legal?

    - by user1055638
    Lets say we have these packages and classes: package p1; public class A1 { public static void a() {} } package p2; public class A1 { public static void a() {} } package p3; import static p1.A1.a; import static p2.A1.a; public class A1 { public static void test() { } } I am wondering, why the static import of methods is legal (won't result in compile time error) in package p3? We won't be able to use them further in the test() method as such usage will result in the compile time error. Why it is not the same as with a normal import of classes. Lets say we would like to import classes A1 from packages p1 and p2 into p3: package p3; import p1.A1; import p2.A1; such import is illegal and will result in the compile time error.

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  • OSGI, Servlets and JPA hello world / tutorial / example

    - by Kamil
    I want to build a web application which basically is a restful web-service serving json messages. I would like it to be as simple as possible. I was thinking about using servlets (with annotations). JPA as a database layer is a must - Toplink or Hibernate. Preferably working on Tomcat. I want to have app divided into modules serving different functionality (auth service, customer service, etc..). And I would like to be able to update those modules without reinstalling whole application on the server - like eclipse plugins, user is notified (when he enters webapp's home url) that update is available, clicks it, and app is downloading and installing updated module. I think this functionality can be made with OSGI, but I can't find any example code, or tutorial with simple hello world updatable servlet providing some data from database through jpa. I'm looking for an advice: - Is OSGI the right tool for this or it can be done with something simpler? - Where can I find some examples covering topic (or topics) which I need for this project. - Which OSGI implementation would be best-simplest for this task. *My knowledge of OSGI is basic. I know how bundles are described, I understand concept of OSGI container and what it does. I have never created any OSGI app yet.

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  • Make XStream ignore one specific private variable

    - by Tigraine
    Hi guys, I have a little problem with a class I am currently writing a save function for. I'm using XStream (com.thoughtworks.xstream) to serialize a class to XML using the DOMDriver. The class looks like this: public class World { private Configuration config; public World(Configuration config) { this.config = config; } } So, the issue here is that I do not want to serialize Configuration when serializing world, rather I'd like to give XStream a preconstructed Configuration instance when calling fromXml(). Problem here is mainly class design, Configuration holds a private reference to the GUI classes and therefore serializing Configuration means serializing the whole application completely with GUI etc.. And that's kind of bad. Is there a way to instruct XStream to not serialize the private field config, and upon load supply XStream with a configuration instance to use? greetings Daniel

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  • Spring vs Hibernate

    - by Vidar
    Just trying to get my head round Spring and figuring out how I wire up an Oracle connection in xml config file, and now find out I need yet another framework! - Hibernate, this is soooo frustrating as it feels like I'm getting deeper and deeper into more and more frameworks without actually getting what I need done! I looked at Hibernate and it seems to do similar things to Spring, bearing in mind I just want to do some SQL inserts in Oracle. I am reluctant and do not have time to learn 2 frameworks - could I get away with just adopting Hibernate for the simple things I need to do?

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  • How does the event dispatch thread work?

    - by Roman
    With the help of people on stackoverflow I was able to get the following working code of the simples GUI countdown (it just displays a window counting down seconds). My main problem with this code is the invokeLater stuff. As far as I understand the invokeLater send a task to the event dispatching thread (EDT) and then the EDT execute this task whenever it "can" (whatever it means). Is it right? To my understanding the code works like that: In the main method we use invokeLater to show the window (showGUI method). In other words, the code displaying the window will be executed in the EDT. In the main method we also start the counter and the counter (by construction) is executed in another thread (so it is not in the event dispatching thread). Right? The counter is executed in a separate thread and periodically it calls updateGUI. The updateGUI is supposed to update GUI. And GUI is working in the EDT. So, updateGUI should also be executed in the EDT. It is why the code for the updateGUI is inclosed in the invokeLater. Is it right? What is not clear to me is why we call the counter from the EDT. Anyway it is not executed in the EDT. It starts immediately a new thread and the counter is executed there. So, why we cannot call the counter in the main method after the invokeLater block? import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; public class CountdownNew { static JLabel label; // Method which defines the appearance of the window. public static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. public static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText("You have " + i + " seconds."); } } ); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); counter.start(); } }); } }

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  • Hibernate: how to maintain insertion order

    - by jwaddell
    I have a list of entities where creation order is important, but they do not contain a timestamp to use for sorting. Entities are added to the end of the list as they are created so they will be ordered correctly in the list itself. After persisting the list using Hibernate the entities appear in the database table in the order that they were created. However when retrieving the list using a new Hibernate session the list is now in reverse order of insertion/creation. Is this expected behaviour? Is there any way to retrieve the list in the same order as it appears in the table? The primary key is a UUID, and the list of entities should always have been created on the same IP address and JVM. This mean sorting by UUID is a possibility but I'd rather not make assumptions. Another possibility is if the list is guaranteed to always come out in reverse order I could always just work through it backwards.

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  • Encrypt string with public key only

    - by vlahovic
    i'm currently working on a android project where i need to encrypt a string using 128 bit AES, padding PKCS7 and CBC. I don't want to use any salt for this. I've tried loads of different variations including PBEKey but i can't come up with working code. This is what i currently have: String plainText = "24124124123"; String pwd = "BobsPublicPassword"; byte[] key = pwd.getBytes(); key = cutArray(key, 16); byte[] input = plainText.getBytes(); byte[] output = null; SecretKeySpec keySpec = null; keySpec = new SecretKeySpec(key, "AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding"); cipher.init(Cipher.ENCRYPT_MODE, keySpec); output = cipher.doFinal(input); private static byte[] cutArray(byte[] arr, int length){ byte[] resultArr = new byte[length]; for(int i = 0; i < length; i++ ){ resultArr[i] = arr[i]; } return resultArr; } Any help appreciated //Vlahovic

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  • Clean way to combine multiple jars? Preferably using ant

    - by Jacob
    I have runtime dependencies on some external jars that I would like to "rejar" into a single jar. These external dependencies are stored in a external_jars directory, and I'd like to be able to not have to list each one out (e.g., to not need to change my build scripts if my dependencies change). Any thoughts? Google gave me a good answer on how to do this if you don't mind listing out each jar you want as a dependency: http://markmail.org/message/zijbwm46maxzzoo5 Roughly, I want something along the lines of the following, which would combine all jars in lib into out.jar (with some sane overwrite rules). jar -combine -out out.jar -in lib/*.jar

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  • XML parse file from HTTP

    - by Travis
    I have an XML file located at a location such as http://example.com/test.xml I'm trying to parse the XML file to use it in my program with xPath like this but it is not working. Document doc = builder.parse(new File(url)); How can I get the XML file?

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  • Maven - 'all' or 'parent' project for aggregation?

    - by disown
    For educational purposes I have set up a project layout like so (flat in order to suite eclipse better): -product | |-parent |-core |-opt |-all Parent contains an aggregate project with core, opt and all. Core implements the mandatory part of the application. Opt is an optional part. All is supposed to combine core with opt, and has these two modules listed as dependencies. I am now trying to make the following artifacts: product-core.jar product-core-src.jar product-core-with-dependencies.jar product-opt.jar product-opt-src.jar product-opt-with-dependencies.jar product-all.jar product-all-src.jar product-all-with-dependencies.jar Most of them are fairly straightforward to produce. I do have some problem with the aggregating artifacts though. I have managed to make the product-all-src.jar with a custom assembly descriptor in the 'all' module which downloads the sources for all non-transitive deps, and this works fine. This technique also allows me to make the product-all-with-dependencies.jar. I however recently found out that you can use the source:aggregate goal in the source plugin to aggregate sources of the entire aggregate project. This is also true for the javadoc plugin, which also aggregates through the usage of the parent project. So I am torn between my 'all' module approach and ditching the 'all' module and just use the 'parent' module for all aggregation. It feels unclean to have some aggregate artifacts produced in 'parent', and others produced in 'all'. Is there a way of making an 'product-all' jar in the parent project, or to aggregate javadoc in the 'all' project? Or should I just keep both? Thanks

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  • gae xmpp outbound service

    - by cometta
    currently i create xmppservlet like below public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException { JID jid = new JID("[email protected]"); Message msg = new MessageBuilder() .withRecipientJids(jid) .withBody("hi Hello i'm a fancy GAE app, how are you?") .build(); XMPPService xmpp = XMPPServiceFactory.getXMPPService(); SendResponse status = xmpp.sendMessage(msg); } by doing this, from [email protected], i need to send a message to [email protected] only, will [email protected] send out the message back to [email protected]. Is there anyway to programatically send out xmpp message without having [email protected] to initial chat window with [email protected] and send the first message? This should be consider outbound-service right? how to do this?

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  • Parsing XML wont display all items.

    - by Nauman A
    I have this code but the toast wont display any message what is wrong with my code.. I can get the value from link, linknext but title wont bring out any value. ( I am not very bright with writing code so please suggest anything you may feel like. final Button button = (Button) findViewById(R.id.Button01); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // Perform action on click try { URL url = new URL( "http://somelink.com=" + Link.setFirst_link); DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document doc = db.parse(new InputSource(url.openStream())); doc.getDocumentElement().normalize(); NodeList nodeList = doc.getElementsByTagName("item"); /** Assign textview array lenght by arraylist size */ for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); Element fstElmnt = (Element) node; NodeList nameList = fstElmnt.getElementsByTagName("link"); Element nameElement = (Element) nameList.item(0); nameList = nameElement.getChildNodes(); String img = (((Node) nameList.item(0)).getNodeValue()); NodeList websiteList = fstElmnt.getElementsByTagName("linknext"); Element websiteElement = (Element) websiteList.item(0); websiteList = websiteElement.getChildNodes(); String nextlink = (((Node) websiteList.item(0)).getNodeValue()); Link.setFirst_link = nextlink; Drawable drawable = LoadImageFromWebOperations(img); imgView.setImageDrawable(drawable); NodeList titleList = fstElmnt.getElementsByTagName("title"); Element titleElement = (Element) titleList.item(0); websiteList = titleElement.getChildNodes(); String title = (((Node) titleList.item(0)).getNodeValue()); Context context = getApplicationContext(); CharSequence text = title; int duration = Toast.LENGTH_SHORT; Toast toast = Toast.makeText(context, text, duration); toast.show(); } } catch (Exception e) { System.out.println("XML Pasing Excpetion = " + e); } } }); /** Set the layout view to display */ } Here is the xml file <?xml version="1.0"?> <maintag> <item> <link>http://image.com/357769.jpg?40</link> <linknext>http://www.image.com</linknext> <title>imagename</title> </item> </maintag>

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  • Listener to prevent System.out display on the screen.

    - by harshit
    Hi, I was doing my academic project and while building and testing i have put many println() statements. But when I had to submit all prints should not be displayed. Can i implement something like listener which will be invoked when System.out is tried to be executed and prevents it from displaying. I dont know how feasible this idea is but just want to know whether its possible or not. I know i could have used a log file or write into a file but again its just a thought came into my mind if I have to disable SOP how can i do it .. thanks

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