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  • Should I use a collection here?

    - by Eva
    So I have code set up like this: public interface IInterface { public void setField(Object field); } public abstract class AbstractClass extends JPanel implements IInterface { private Object field_; public void setField(Object field) { field_ = field; } } public class ClassA extends AbstractClass { public ClassA() { // unique ClassA constructor stuff } public Dimension getPreferredSize() { return new Dimension(1, 1); } } public class ClassB extends AbstractClass { public ClassB() { // unique ClassB constructor stuff } public Dimension getPreferredSize() { return new Dimension(42, 42); } } public class ConsumerA { public ConsumerA(Collection<AbstractClass> collection) { for (AbstractClass abstractClass : collection) { abstractClass.setField(this); abstractClass.repaint(); } } } All hunky-dory so far, until public class ConsumerB { // Option 1 public ConsumerB(ClassA a, ClassB b) { methodThatOnlyTakesA(a); methodThatOnlyTakesB(b); } // Option 2 public ConsumerB(Collection<AbstractClass> collection) { for (IInterface i : collection) { if (i instanceof ClassA) { methodThatOnlyTakesA((ClassA) i); else if (i instanceof ClassB) { methodThatOnlyTakesB((ClassB) i); } } } } public class UsingOption1 { public static void main(String[] args) { ClassA a = new ClassA(); ClassB b = new ClassB(); Collection<AbstractClass> collection = Arrays.asList(a, b); ConsumerA consumerA = new ConsumerA(collection); ConsumerB consumerB = new ConsumerB(a, b); } } public class UsingOption2 { public static void main(String[] args) { Collection<AbstractClass> collection = Arrays.asList(new ClassA(), new ClassB()); ConsumerA = new ConsumerA(collection); ConsumerB = new ConsumerB(collection); } } With a lot more classes extending AbstractClass, both options get unwieldly. Option1 would make the constructor of ConsumerB really long. Also UsingOption1 would get long too. Option2 would have way more if statements than I feel comfortable with. Is there a viable Option3? If it helps, ClassA and ClassB have all the same methods, they're just implemented differently. Thanks for slogging through my code!

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  • Setting log level of message at runtime in slf4j

    - by scompt.com
    When using log4j, the Logger.log(Priority p, Object message) method is available and can be used to log a message at a log level determined at runtime. We're using this fact and this tip to redirect stderr to a logger at a specific log level. slf4j doesn't have a generic log() method that I can find. Does that mean there's no way to implement the above?

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  • server push or client push is better ?

    - by akshay
    I am developing a chat website using jsp/servlet.I will be hosting my website on gooogle appengine .Now i have some doubts regarding whether to use server push or client pull technology 1)If i use server push and if i dont close the response of servlet will it cause the server to go slow?How many simultanious connection can a tyicall tomcat server can handle if i keep the socket open for the entire chat session between 2 clinets?? 2)Will server push or clinet push be better??

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  • Eclipse plugin development for Eclipse

    - by Raven
    Hi, how do I start to develop a plugin for Eclipse? I need a tool which isn't out there yet for my further development... so my main concerns are: -How to add a perspective? -How to add menu items? -How to add a view into the "Show Views" menu? -How to add to the preference pane? -How do I get information, like * where is the workspace? * which files are open in the editor? * which projects are collapsed / expanded in the left projects view? * ..... -Which conventions (naming...) should I consider? -How to set up update site/deployment? Can you give me some hints, links, tutorials.... Dont get me wrong. I am using Eclipse RCP for developing stand alone apps for quite some time, so I am familiar with the techniques, but I never started to develop a plugin for Eclipse itself. Thanks

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  • JMS Topic vs Queue - Intent

    - by Sandeep Jindal
    I am trying to understand on the design requirements for using Queue, and could not find this question (with answer). My understanding: Queue means one-to-one. Thus it would be used in a special case (if not rare, very few cases) when a designer is sure that the message would be intended for only one consumer. But even in those cases, I may want to use Topic (just to be future safe). The only extra case I would have to do is to make (each) subscription durable. Or, I special situations, I would use bridging / dispatcher mechanism. Give above, I would always (or in most cases) want to publish to a topic. Subscriber can be either durable topic(s) or dispatched queue(s). Please let me know what I am missing here or I am missing the original intent?

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  • Google App Engine ClassNotPersistenceCapableException

    - by Frank
    I have the following class : import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.appengine.api.datastore.*; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class PayPal_Message { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) private Long id; @Persistent private Text content; @Persistent private String time; public PayPal_Message(Text content,String time) { this.content=content; this.time=time; } public Long getId() { return id; } public Text getContent() { return content; } public String getTime() { return time; } public void setContent(Text content) { this.content=content; } public void setTime(String time) { this.time=time; } } It used to be in a package, and works fine, now I put all classes in the default package, which caused me this error : org.datanucleus.jdo.exceptions.ClassNotPersistenceCapableException: The class "The class "PayPal_Message" is not persistable. This means that it either hasnt been enhanced, or that the enhanced version of the file is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-Data/annotations for the class are not found." is not persistable. This means that it either hasnt been enhanced, or that the enhanced version of the file is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-Data for the class is not found. NestedThrowables: org.datanucleus.exceptions.ClassNotPersistableException: The class "PayPal_Message" is not persistable. This means that it either hasnt been enhanced, or that the enhanced version of the file is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-Data/annotations for the class are not found. What should I do to fix it ?

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  • How to change the cursor type

    - by Jessy
    This question is related to the previous post. http://stackoverflow.com/questions/2532936/how-to-save-file-and-read How can I change the cursor to "Hand" only when the mouse pointed on grid which is not Null (contained images)? So far the cursor turn to "Hand" all over the grids (null or not null). public GUI() { .... JPanel pDraw = new JPanel(); .... for(Component component: pDraw.getComponents()){ JLabel lbl = (JLabel)component; //add mouse listener to grid box which contained image if (lbl.getIcon() != null) lbl.addMouseListener(this); } public void mouseEntered(MouseEvent e) { Cursor cursor = Cursor.getDefaultCursor(); //change cursor appearance to HAND_CURSOR when the mouse pointed on images cursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR); setCursor(cursor); }

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  • Configure WebLogic MDB to listen to Foreing AMQ Server

    - by eliel.lobo
    I'm trying to create an MDB(EJB 3.0) on WebLogic 10.3.5. to listen to a Queue in an external AMQ server. but after much work and combination of tutorials i get the followin error when deployin on WwebLogic. [EJB:015027]The Message-Driven EJB is transactional but JMS connection factory referenced by the JNDI name: ActiveMQXAConnectionFactory is not a JMS XA connection factory. Here is a brief of the work i have done: I have added the corresponding libraries to my WLS classpath (following thos tuturial http://amadei.com.br/blog/index.php/connecting-weblogic-and-activemq) and I have created the corresponding JMS Modules as indicated in the tutorial. As connection factory I have used ActiveMQConnectionFactory initially and ActiveMQXAConnectionFactory later, I also ignome the jms. notation an just put plain names as testQueue. Then create a simple MDB whit the following structure. I explicitly defined "connectionFactoryJndiName" property because otherwise it assumes a WebLogic connection factory which is not found an then raises an error. @MessageDriven( activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "testQueue"), @ActivationConfigProperty(propertyName = "connectionFactoryJndiName", propertyValue = "ActiveMQXAConnectionFactory") }, mappedName = "testQueue") public class ROMELReceiver implements MessageListener { /** * Default constructor. */ public ROMELReceiver() { // TODO Auto-generated constructor stub } /** * @see MessageListener#onMessage(Message) */ public void onMessage(Message message) { System.out.println("Message received"); } } At this point I'm stuck with the error mentioned above. Even though I use ActiveMQXAConnectionFactory instead of simply ActiveMQConnectionFactory, JNDI resources tree in web logic server shows org.apache.activemq.ActiveMQConnectionFactory as class for my configured connection factory. am i missing something? or is this just a completely wrong way to connect WebLogic whith AMQ? Thanks in advance.

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  • Why is an oracle sequence named hibernate_sequence being created with JPA using Hibernate with the O

    - by JavaRocky
    All my entities use this type of @Id @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MYENTITY_SEQ") @SequenceGenerator(name = "MYENTITY_SEQ", sequenceName = "MYENTITY_SEQ") @Column(name = "MYENTITY", nullable = false) private Long id; Or @Id @Column(name = "MYENTITY") I find that an oracle sequence named hibernate_sequence is always created. Why is this so? And how can i avoid this? I am using JPA1 with Hibernate 3 and the Oracle 10g dialect.

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  • Android OutOfMemoryError - Loading JSON File

    - by jeremynealbrown
    The app I am working on needs to read a JSON file that may be anywhere from 1.5 to 3 MB in size. It seems to have no problem opening the file and converting the data to a string, but when it attempts to convert the string to a JSONArray, OutOfMemoryErrors are thrown. The exceptions look something like this: E/dalvikvm-heap( 5307): Out of memory on a 280-byte allocation. W/dalvikvm( 5307): Exception thrown (Ljava/lang/OutOfMemoryError;) while throwing internal exception (Ljava/lang/OutOfMemoryError;) One strange thing about this is that the crash only occurs every 2nd or 3rd time the app is run, leaving me to believe that the memory consumed by the app is not being garbage collected each time the app closes. Any insight into how I might get around this issue would be greatly appreciated. I am open to the idea of loading the file in chunks, but I'm not quite sure what the best approach is for such a task. Thank you

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  • Apache POI Comment Excel

    - by Marquinio
    I need to add a comment to an HSSF Cell in Excel. Everything works fine the very first time but if I open the same file and run the code again it corrupts the file. I've also noticed that I need to create a Drawing object on a Sheet only once: _sheet.createDrawingPatriarch(); If the line above gets executed more than once comments will not work. So has anyone tried adding comments to Cells, closing the file, opening the file again and trying to add more comments to different cells? The below code works but if I open the file again then comments are not added, plus the file gets corrupted!!! Is there a way to get the existing Drawing object from a Sheet? Any ideas appreciated. Thanks!! _drawing = (HSSFPatriarch) _sheet.createDrawingPatriarch(); Row row = _sheet.getRow(rowIndex_); Cell cell = row.getCell(0); CreationHelper factory = _workbook.getCreationHelper(); HSSFAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, (short)4, 2, (short)6, 5); org.apache.poi.ss.usermodel.Comment comment = _drawing.createComment(anchor); RichTextString str = factory.createRichTextString("Hello, World "+rowIndex_); comment.setString(str); cell.setCellComment(comment);

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  • JDK 1.6 compatible with JDK 1.5??

    - by kojh
    Im having a compatible issue, my project is develop in JDK 1.6, but when i need to post it to a host domain, there is a issue where the host domain used JDK 1.5, how do i make my project compatible with JDK 1.5? thanks in advance

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  • Equinox config.ini generated

    - by asrijaal
    Hi there, I've got some osgi plugin development going on. I've created a launch configuration in my eclipse IDE, which adds all required bundles to my runtime. Is there any possibilty to export/convert the eclipse launch config to a config.ini which I can use on my standalone equinox env?

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  • Android: Context menu doesn't show up for ListView with members defined by LinearLayout?

    - by RandomEngy
    I've got a ListActivity and ListView and I've bound some data to it. The data shows up fine, and I've also registered a context menu for the view. When I display the list items as just a simple TextView, it works fine: <TextView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/nametext" android:layout_width="wrap_content" android:layout_height="wrap_content"/> However when I try something a bit more complex, like show the name and a CheckBox, the menu never shows up: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal"> <TextView android:id="@+id/nametext" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <CheckBox android:id="@+id/namecheckbox" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> Can long-presses work on more complex elements? I'm building on 2.1.

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  • Using AWT components inside a JInnerFrame (for JDesktopPane)

    - by Jack
    Hello, is there a way to hack bugs related to adding an AWT component (in my case a PApplet, so a processing language sketch) inside a JInternalFrame? It works but not as intended, since it flickers and dragging the frame causes repaint issues.. reading around it seems that, althrough it's possible to mix heavyweight (AWT) and lightweight (Swing) components some problems seem to be unavoidable.. is it true? Thanks!

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  • What is the regular expression for valdating a 'price' in a jtextfield

    - by wniroshan
    I want to validate a jtextfield as user inputs a price of some item. I have a perfectly working code which beeps and discard if user inputs some character that doesnt match the regular expression.(for regular expression "[0-9]+" it accepts any number of digits and beeps if a letter is given as input) But the problem is I want to validate an input like "12500.00". Format should be any number of digits before decimal point and two digits after the decimal point. eg: ddd.dd I tried the following regular expression. But the i doesnt allow user to input "." character. It allows user to input any number of digits but when "." key is pressed input is not accepted. here is the regular expression I used. "[0-9]+ | [0-9]+. | [0-9]+.[0-9]{1} | [0-9]+{2}" important: user input is validated character by character as the user inputs them to the jtextfield.

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  • Best way to fetch data from a single database table with multiple threads?

    - by Ravi Bhatt
    Hi, we have a system where we collect data every second on user activity on multiple web sites. we dump that data into a database X (say MS SQL Server). we now need to fetch data from this single table from daatbase X and insert into database Y (say mySql). we want to fetch time based data from database X through multiple threads so that we fetch as fast as we can. Once fetched and stored in database Y, we will delete data from database X. Are there any best practices on this sort of design? any specific things to take care on table design like sharing or something? Are there any other things that we need to take care to make sure we fetch it as fast as we can from threads running on multiple machines? Thanks in advance! Ravi

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  • MySQLNonTransientConnectionException in jdbc program at run time

    - by Sunil Kumar Sahoo
    Hi I have created jdbc mysql connection. my program works fine for simple execution of query. But if i run the same program for more than 10 hour and execute query then i receives the following mysql exception. I have not used close() method anywhere. i created database connection and opened it forever and always execute query. there is no where that i explicitly mentioned timeout for connection. i am unable to identify the problem com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after statement closed. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sample code for database connection: String driver = PropertyReader.getDriver(); String url = dbURLPath; Class.forName(driver); connectToServerDB = DriverManager.getConnection(url); connectToServerDB.setAutoCommit(false);

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  • Problem with detecting the value of the drop down list on the server (servlet) side

    - by Harry Pham
    Client code is pretty simple: <form action="DDServlet" method="post"> <input type="text" name="customerText"> <select id="customer"> <option name="customerOption" value="3"> Tom </option> <option name="customerOption" value="2"> Harry </option> </select> <input type="submit" value="send"> </form> Here is the code on the Servlet Enumeration paramNames = request.getParameterNames(); while(paramNames.hasMoreElements()){ String paramName = (String)paramNames.nextElement(); //get the next element System.out.println(paramName); } When I print out, I only see, customerText, but not customerOption. Any idea why guys? What I hope is, if I select Tom in my option, once I submit, on my servlet I should able to do this: String paramValues[] = request.getParameterValues(paramName); and get back value of 3

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