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  • Partially constructed object / Multi threading

    - by reto
    Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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  • Properly removing an Integer from a List<Integer>

    - by Yuval A
    Here's a nice pitfall I just encountered. Consider a list of integers: List<Integer> list = new ArrayList<Integer>(); list.add(5); list.add(6); list.add(7); list.add(1); Any educated guess on what happens when you execute list.remove(1)? What about list.remove(new Integer(1))? This can cause some nasty bugs. What is the proper way to differentiate between remove(int index), which removes an element from given index and remove(Object o), which removes an element by reference, when dealing with lists of integers? The main point to consider here is the one @Nikita mentioned - exact parameter matching takes precedence over auto-boxing.

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  • Does Hibernate always need a setter when there is a getter?

    - by Marcus
    We have some Hibernate getter methods annotated with both @Column and @Basic. We get an exception if we don't have the corresponding setter. Why is this? In our case we are deriving the value returned from the getter (to get stored in the DB) and the setter has no functional purpose. So we just have an empty method to get around the error condition..

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  • JToolbar is hidden by JMenu

    - by pierre
    I'm using Netbeans to add a JToolbar to my window which also has a JMenuBar. Here is the design-time look: .. but during run-time I get this: With the toolbar seemingly partially hidden under the menu names. This is on the Mac, btw. Is there something stupid I've forgotten to do or some layout trick I should be using? EDIT: I'll add that the area below the toolbar is a SplitContainer.

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  • How can I set the name of the class xml by constructor?

    - by spderosso
    Hi, I want to be able to do something like this: @Root(name="events") class XMLEvents { @ElementList(inline=true) ArrayList<XMLEvent> events = Lists.newArrayList(); XMLEvents(){ ... events.add(new XMLEvent(time, type, professorP)); events.add(new XMLEvent(time, type, student)); events.add(new XMLEvent(time, type, course)); ... } } The XMLEvent class to go something like: class XMLEvent { @Root(name="professor") XMLEvent(DateTime time, LogType type, Professor p){ ... } @Root(name="student") XMLEvent(DateTime time, LogType type, Student st){ ... } @Root(name="course") XMLEvent(DateTime time, LogType type, Course c){ ... } } For the output to be: <events> <professor> ... </professor> <student> ... </student> <course> ... </course> </events> So depending on the constructor I call to create a new XMLEvent the root name to which is mapped is different. Is this even possible? Of course the past example was just to transmit what I need. Putting the @Root annotation there didn't change anything Thanks!

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  • Single log file for multiple webapps

    - by Ashish Aggarwal
    In my tomcat there are multiple webapps deployed and they communicate with each other. Currently they all have their own log file. But when there is some issue comes from call I have to 1st check with the app to whom I made a call and check log file of respective apps involved in the call. So I want that, as all apps is deployed in same tomcat and sharing a common log4j, if a call made to any app then all logs should be in a single log file and no matters how my webapps are involved all error comes from any webapp during the call should be in a single log file. I have no idea how can I achieve this. So any help is appreciable. Edited: I think my question is not cleared so updated with use case: I have three webapps A, B, C having logs files as A.log, B.log and C.log. I made two calls. 1st one to A (that internally calls C) and 2nd to B (that internally calls C). Now logging of first call must be in A.log (with the logs of every step performed inside the webapp c) and second call must be in B.log (with the logs of every step performed inside the webapp c).

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  • Migrate existing Maven Project into an OSGI Bundle

    - by user1706291
    i am new to the whole OSGi stuff and my task is to create an OSGi Bundle out from an exisitng maven project. To get started i decided to pick the smallest part and starting with it: Here is the pom.xml project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <artifactId>cross</artifactId> <groupId>net.sf.maltcms</groupId> <version>1.2.12-SNAPSHOT</version> </parent> <artifactId>cross-main</artifactId> <packaging>jar</packaging> <name>cross-main</name> <dependencies> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-annotations</artifactId> <version>${project.version}</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-event</artifactId> <version>${project.version}</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-tools</artifactId> <version>${project.version}</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-exception</artifactId> <version>${project.version}</version> </dependency> <dependency> <groupId>commons-codec</groupId> <artifactId>commons-codec</artifactId> <version>1.4</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-main-api</artifactId> <version>${project.version}</version> <exclusions> <exclusion> <artifactId>commons-logging</artifactId> <groupId>commons-logging</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>3.0.6.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-asm</artifactId> <version>3.0.6.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>3.0.6.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>3.0.6.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.0.6.RELEASE</version> <exclusions> <exclusion> <artifactId>commons-logging</artifactId> <groupId>commons-logging</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-expression</artifactId> <version>3.0.6.RELEASE</version> </dependency> <dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.1</version> </dependency> <dependency> <groupId>net.sf.ehcache</groupId> <artifactId>ehcache-core</artifactId> <version>2.4.6</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>cross-math</artifactId> <version>${project.version}</version> </dependency> <dependency> <groupId>com.db4o</groupId> <artifactId>db4o-all</artifactId> <version>8.0.249</version> </dependency> <dependency> <groupId>net.sf.mpaxs</groupId> <artifactId>mpaxs-spi</artifactId> <version>1.6.10</version> </dependency> <dependency> <groupId>net.sf.mpaxs</groupId> <artifactId>mpaxs-server</artifactId> <version>1.6.10</version> </dependency> </dependencies> I did some research and found the Apache Bundle Plugin for maven and changed the pom to this <packaging>bundle</packaging> and added <build> <plugins> <plugin> <groupId>org.apache.felix</groupId> <artifactId>maven-bundle-plugin</artifactId> <extensions>true</extensions> <configuration> <instructions> <Bundle-SymbolicName>${pom.artifactId}</Bundle-SymbolicName> </instructions> </configuration> </plugin> </plugins> </build> mvn clean install went fine and i got a jar file containing the manifest, but of course the bundle could not be resolved BundleException: The bundle "cross-main_1.2.12.SNAPSHOT [30]" could not be resolved. Reason: Missing Constraint: Import-Package: com.db4o; version="[8.0.0,9.0.0) To make a long story short: What are the possibiliteis to migrate a maven application into an OSGi Bundle? Espacially how to manage the dependencys

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  • Why aren't arrays expandable?

    - by Mustafa
    When we create an array, we cannot change its size; it's fixed. OK, seems nice, we can create a new bigger array and copy the values one by one and that's little slow. What's the technical background of it?

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  • Catching constraint violations in JPA 2.0.

    - by Dennetik
    Consider the following entity class, used with, for example, EclipseLink 2.0.2 - where the link attribute is not the primary key, but unique nontheless. @Entity public class Profile { @Id private Long id; @Column(unique = true) private String link; // Some more attributes and getter and setter methods } When I insert records with a duplicate value for the link attribute, EclipseLink does not throw a EntityExistsException, but throws a DatabaseException, with the message explaining that the unique constraint was violated. This doesn't seem very usefull, as there would not be a simple, database independent, way to catch this exception. What would be the advised way to deal with this? A few things that I have considered are: Checking the error code on the DatabaseException - I fear that this error code, though, is the native error code for the database; Checking the existence of a Profile with the specific value for link beforehand - this obviously would result in an enormous amount of superfluous queries.

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  • collection of system properties using web browser

    - by vishwa
    hi i am doing distributed computing environment........For the applications need to get distributed to different clients connected to the server in the network,i prefered to collect the client's system properties like free memory available in the client's system,so that i could distribute d application according to that efficiently......so kindly project me wth some idea.thanks in advance

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  • Documenting logic in javadoc

    - by smayers81
    I have a question about where to document logic in javadocs. For example, I have the following method signature in an interface: public int getTotalAssociationsAsParent(Long id, Long type); The method returns associations where the given ID is the parent and the association is of type 'type'. ID is required, but if type passed in is NULL, then I will return ALL associations where the ID is the parent. My question is where should this type of logic be documented? I hesitate putting it in the javadoc of the interface because that sort of constrains all implementing classes to adhere to that logic. Maybe in the future, I'll have an Impl class that throws an IllegalArgumentException if type is NULL. However, if I put it in non-javadoc in the Impl class, then consumers of this method won't know how the method behaves with a NULL type.

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  • Change classloader

    - by Chris
    I'm trying to switch the class loader at runtime: public class Test { public static void main(String[] args) throws Exception { final InjectingClassLoader classLoader = new InjectingClassLoader(); Thread.currentThread().setContextClassLoader(classLoader); Thread thread = new Thread("test") { public void run() { System.out.println("running..."); // approach 1 ClassLoader cl = TestProxy.class.getClassLoader(); try { Class c = classLoader.loadClass("classloader.TestProxy"); Object o = c.newInstance(); c.getMethod("test", new Class[] {}).invoke(o); } catch (Exception e) { e.printStackTrace(); } // approach 2 new TestProxy().test(); }; }; thread.setContextClassLoader(classLoader); thread.start(); } } and: public class TestProxy { public void test() { ClassLoader tcl = Thread.currentThread().getContextClassLoader(); ClassLoader ccl = ClassToLoad.class.getClassLoader(); ClassToLoad classToLoad = new ClassToLoad(); } } (it is not relevant what the InjectingClassLoader is) I'd like to make the result of "approach 1" and "approach 2" exactly same, but it looks like thread.setContextClassLoader(classLoader) does nothing and the "approach 2" always uses the system classloader (can be determined by comparing tcl and ccl variables while debugging). Is it possible to make all classes loaded by new thread use given classloader?

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  • Accessing global variable in multithreaded Tomcat server

    - by jwegan
    I have a singleton object that I construct like thus: private static volatile KeyMapper mapper = null; public static KeyMapper getMapper() { if(mapper == null) { synchronized(Utils.class) { if(mapper == null) { mapper = new LocalMemoryMapper(); } } } return mapper; } The class KeyMapper is basically a synchronized wrapper to HashMap with only two functions, one to add a mapping and one to remove a mapping. When running in Tomcat 6.24 on my 32bit Windows machine everything works fine. However when running on a 64 bit Linux machine (CentOS 5.4 with OpenJDK 1.6.0-b09) I add one mapping and print out the size of the HashMap used by KeyMapper to verify the mapping got added (i.e. verify size = 1). Then I try to retrieve the mapping with another request and I keep getting null and when I checked the size of the HashMap it was 0. I'm confident the mapping isn't accidentally being removed since I've commented out all calls to remove (and I don't use clear or any other mutators, just get and put). The requests are going through Tomcat 6.24 (configured to use 200 threads with a minimum of 4 threads) and I passed -Xnoclassgc to the jvm to ensure the class isn't inadvertently getting garbage collected (jvm is also running in -server mode). I also added a finalize method to KeyMapper to print to stderr if it ever gets garbage collected to verify that it wasn't being garbage collected. I'm at my wits end and I can't figure out why one minute the entry in HashMap is there and the next it isn't :(

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  • What web UI framework is most suitable for building dynamic pages / forms?

    - by waxwing
    Hello, We are at a stage where we are considering different Web UI frameworks (most likely component based ones such as GWT, JSF, Wicket, Vaadin, etc). One of the main use cases / constraints is that it must support generating dynamic pages. I.e., the page/form layout and components is stored in a database and is changeable at runtime, and from this pages are generated. We are also going to write static layouts, but that is not the main focus of this question. I thought maybe the user community here can share experiences of different frameworks in this context. Are there differences in ease of implementation and what is suitable?

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  • Quartz scheduler theadpool

    - by Shamik
    The SimpleThreadPool class shipped along with Quartz Scheduler does not have a FIFO behavior. I want to make sure if I keep adding jobs to the scheduler, they are addressed in a First - in - First - out basis. Is there any ThreadPool available for this ? Or is there any other way to achieve this?

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  • What is the relation between ContentPane and JPanel?

    - by Roman
    I found one example in which buttons are added to panels (instances of JPanel) then panels are added to the the containers (instances generated by getContentPane) and then containers are, by the construction, included into the JFrame (the windows). I tried two things: I got rid of the containers. In more details, I added buttons to a panel (instance of JPanel) and then I added the panel to the windows (instance of JFrame). It worked fine. I got rid of the panels. In more details, I added buttons directly to the container and then I added the container to the window (instance of JFrame). So, I do not understand two things. Why do we have two competing mechanism to do the same things. What is the reason to use containers in combination with the panels (JPanel)? (For example, what for we include buttons in JPanels and then we include JPanels in the Containers). Can we include JPanel in JPanel? Can we include a container in container?

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  • JTextField that has inner fields or preformated format, something like the ip field in windows

    - by dimitar
    Hello guys, i want to create a text field that will be for date and will have dd.mm.YYYY format. Now what i want to do is the user to type only the numbers, not the dots to. So the field would be like: _ _. _ _ . _ _ _ _ So when the user wants to type the date: 15.05.2010 for example, he will only type the numbers in the sequence 15052010. Also i would like, when he preses on left or right arrow, the cursor to go from one field(not JTextField, but field in the JTextField). So lets say i have JTextField with text in it: 15.05.2010, so if user is on the beginning and he preses right arrow, the cursor to go to the .05 field. I hope you understand me 'cos right now i don't any idea how to make this, or at least how to look for it on google. Thank you.

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  • Why is my GUI unresponsive while a SwingWorker thread runs?

    - by Starchy
    Hello, I have a SwingWorker thread with an IOBound task which is totally locking up the interface while it runs. Swapping out the normal workload for a counter loop has the same result. The SwingWorker looks basically like this: public class BackupWorker extends SwingWorker<String, String> { private static String uname = null; private static String pass = null; private static String filename = null; static String status = null; BackupWorker (String uname, String pass, String filename) { this.uname = uname; this.pass = pass; this.filename = filename; } @Override protected String doInBackground() throws Exception { BackupObject bak = newBackupObject(uname,pass,filename); return "Done!"; } } The code that kicks it off lives in a class that extends JFrame: public void actionPerformed(ActionEvent event) { String cmd = event.getActionCommand(); if (BACKUP.equals(cmd)) { SwingUtilities.invokeLater(new Runnable() { public void run() { final StatusFrame statusFrame = new StatusFrame(); statusFrame.setVisible(true); SwingUtilities.invokeLater(new Runnable() { public void run () { statusFrame.beginBackup(uname,pass,filename); } }); } }); } } Here's the interesting part of StatusFrame: public void beginBackup(final String uname, final String pass, final String filename) { worker = new BackupWorker(uname, pass, filename); worker.execute(); try { System.out.println(worker.get()); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } } So far as I can see, everything "long-running" is handled by the worker, and everything that touches the GUI on the EDT. Have I tangled things up somewhere, or am I expecting too much of SwingWorker?

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  • Get rid of jfreechart chartpanel unnecessary space

    - by ryvantage
    I am trying to get a JFreeChart ChartPanel to remove unwanted extra space between the edge of the panel and the graph itself. To best illustrate, here's a SSCCE (with JFreeChart installed): public static void main(String[] args) { JPanel panel = new JPanel(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.fill = GridBagConstraints.BOTH; gbc.gridwidth = 1; gbc.gridheight = 1; gbc.weightx = 1; gbc.weighty = 1; gbc.gridy = 1; gbc.gridx = 1; panel.add(createChart("Sales", Chart_Type.DOLLARS, 100000, 115000), gbc); gbc.gridx = 2; panel.add(createChart("Quotes", Chart_Type.DOLLARS, 250000, 240000), gbc); gbc.gridx = 3; panel.add(createChart("Profits", Chart_Type.PERCENTAGE, 40.00, 38.00), gbc); JFrame frame = new JFrame(); frame.add(panel); frame.setSize(800, 300); frame.setLocationRelativeTo(null); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } private static ChartPanel createChart(String title, Chart_Type type, double goal, double actual) { double maxValue = goal * 2; double yellowToGreenNum = goal; double redToYellowNum = goal * .75; DefaultValueDataset dataset = new DefaultValueDataset(actual); JFreeChart jfreechart = createChart(dataset, Math.max(actual, maxValue), redToYellowNum, yellowToGreenNum, title, type); ChartPanel chartPanel = new ChartPanel(jfreechart); chartPanel.setBorder(new LineBorder(Color.red)); return chartPanel; } private static JFreeChart createChart(ValueDataset valuedataset, Number maxValue, Number redToYellowNum, Number yellowToGreenNum, String title, Chart_Type type) { MeterPlot meterplot = new MeterPlot(valuedataset); meterplot.setRange(new Range(0.0D, maxValue.doubleValue())); meterplot.addInterval(new MeterInterval(" Goal Not Met ", new Range(0.0D, redToYellowNum.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(255, 0, 0, 128))); meterplot.addInterval(new MeterInterval(" Goal Almost Met ", new Range(redToYellowNum.doubleValue(), yellowToGreenNum.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(255, 255, 0, 64))); meterplot.addInterval(new MeterInterval(" Goal Met ", new Range(yellowToGreenNum.doubleValue(), maxValue.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(0, 255, 0, 64))); meterplot.setNeedlePaint(Color.darkGray); meterplot.setDialBackgroundPaint(Color.white); meterplot.setDialOutlinePaint(Color.gray); meterplot.setDialShape(DialShape.CHORD); meterplot.setMeterAngle(260); meterplot.setTickLabelsVisible(false); meterplot.setTickSize(maxValue.doubleValue() / 20); meterplot.setTickPaint(Color.lightGray); meterplot.setValuePaint(Color.black); meterplot.setValueFont(new Font("Dialog", Font.BOLD, 0)); meterplot.setUnits(""); if(type == Chart_Type.DOLLARS) meterplot.setTickLabelFormat(NumberFormat.getCurrencyInstance()); else if(type == Chart_Type.PERCENTAGE) meterplot.setTickLabelFormat(NumberFormat.getPercentInstance()); JFreeChart jfreechart = new JFreeChart(title, JFreeChart.DEFAULT_TITLE_FONT, meterplot, false); return jfreechart; } enum Chart_Type { DOLLARS, PERCENTAGE } If you resize the frame, you can see that you cannot make the edge of the graph go to the edge of the panel (the panels are outlined in red). Especially on the bottom - there is always a gap between the bottom the graph and the bottom of the panel. Is there a way to make the graph fill the entire area? Is there a way to at least guarantee that it is touching one edge of the panel (i.e., it is touching the top and bottom or the left and right) ??

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