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  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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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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  • How to differentiate between time to live and time to idle in ehcache

    - by Jacques René Mesrine
    The docs on ehache says: timeToIdleSeconds: Sets the time to idle for an element before it expires. i.e. The maximum amount of time between accesses before an element expires timeToLiveSeconds: Sets the time to live for an element before it expires. i.e. The maximum time between creation time and when an element expires. I understand timeToIdleSeconds But does it means that after the creation & first access of a cache item, the timeToLiveSeconds is not applicable anymore ?

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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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  • What is jasper report's algorithm for using a data source?

    - by spderosso
    Hi, I have created my custom data source by implementing the interface JRDataSource. This interface looks like this: public interface JRDataSource { /** * Tries to position the cursor on the next element in the data source. * @return true if there is a next record, false otherwise * @throws JRException if any error occurs while trying to move to the next element */ public boolean next() throws JRException; /** * Gets the field value for the current position. * @return an object containing the field value. The object type must be the field object type. */ public Object getFieldValue(JRField jrField) throws JRException; } My question is the following: In what way does jasper report call this functions for obtaining the fields in the .jrxml. E.g: if( next() )){ call getFieldValue for every field present in the page header while( next() ){ call getFieldValue for every field present in detail part } call getFieldValue for every field present the footer } The previous is just an example, experimentally in fact I found out that it is actually not like that. So my question arised. Thanks!

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  • Restoring web session in struts2

    - by bozo
    Hi, I have a classical scenario of a website and payment gateway integration, where the request for payment is sent to payment processor, and the payment processor calls back my application once it's done with some parameters I passed to it in the original request. Among parameters, we pass jsessionid and we expect that when the remote server makes request to our server (via customer browser redirect to our server) that the session will be the same as the session used to send the initial payment request. This does not happen, we have two different sessions, although the payment processor includes our original jsessionid in the request to us (https://blabla/?jsessionid=something). How should we go about recreating a session in struts2, in the only thing that connects the 'OLD' and 'NEW' session is the jsessionid in the request URL? Any ideas? Is this possible at all or is the 'OLD' session data deleted when the user moves away from our server onto a completely different domain of a payment processor with their data-entry form? This would explain our innability to recreate the session. Thanks a lot for your replies.

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  • Grails , how do I get an object NOT to save

    - by user350325
    Hello I am new to grails and trying to create a form which allows a user to change the email address associated with his/her account for a site I am creating. It asks for the user for their current password and also for the new email address they want to use. If the user enters the wrong password or an invalid email address then it should reject them with an appropriate error message. Now the email validation can be done through constraints in grails, but the password change has to match their current password. I have implemented this check as a method on a service class. See code below: def saveEmail = { def client = ClientUser.get(session.clientUserID) client.email = params.email if(clientUserService.checkPassword(session.clientUserID , params.password) ==false) { flash.message = "Incorrect Password" client.discard() redirect(action:'changeEmail') } else if(!client.validate()) { flash.message = "Invalid Email Address" redirect(action:'changeEmail') } else { client.save(); session.clientUserID = null; flash.message = "Your email address has been changed, please login again" redirect(controller: 'clientLogin' , action:'index') } } Now what I noticed that was odd was that if I entered an invalid email then it would not save the changes (as expected) BUT if I entered the wrong password and a valid email then it would save the changes and even write them back into the database even though it would give the correct "invalid password" error message. I was puzzled so set break points in all the if/else if/else blocks and found that it was hitting the first if statement as expected and not hitting the others , so it would never come accross a call to the save() method, yet it was saved anyway. After a little research I came accross documentation for the discard() method which you can see used in the code above. So I added this but still no avail. I even tried using discard then reloading the client object from the DB again but still no dice. This is very frustrating and I would be grateful for any help, since I think that this should surely not be a complicated requirement!

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  • Refactored App Engine project - now Eclipse is infinitely building the project without end

    - by Yog
    I renamed some files in my App Engine project and refactored code, changing references to variables. Everything seemed fine until I changed the references in the web.xml for the project. Then I got a complaint about some error with the DataNucleus enhancer and now the project build process is stuck at 22%. I tried stopping Eclipse and restarting but the build process keeps hanging. Any tips on how to clean out whatever it's getting stuck on?

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  • Progress bar increment by 1 every 100th of second

    - by Matthew De'Loughry
    I'm trying to get a JProgressBar to increment by 1 every 100th of a second, and at the moment I'm using Thread.sleep(100) inside a while statement like so: try { while (i<=100){ doTime(); } } catch (InterruptedException ex) { Logger.getLogger(SplashScreen.class.getName()).log(Level.SEVERE, null, ex); } public void doTime() throws InterruptedException{ jLabel1.setText("sleeping"); Thread.sleep(100); jLabel1.setText("start"); i++; pb.setValue(i); pb.repaint(); } and If I debug by doing a System.out.println it displays in real time but the swing GUI freezes until it drops out of the while loop can anyone help? thanks matt

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  • Can the JVM recover from an OutOfMemoryError without a restart

    - by askullhead
    Can the JVM recover from an OutOfMemoryError without a restart if it gets a chance to run the GC before more object allocation requests come in? Do the various JVM implementations differ in this aspect? EDIT: My question was about the JVM recovering and not the user program trying to recover by catching the error. In other words if an OOME is thrown in an application server (jboss/websphere/..) do I have to restart it? Or can I let it run if further requests seem to work without a problem. Sorry if that wan't clear.

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  • Getting custom attribute from an Exception thrown during testing

    - by Amit Bhargava
    I'm using JUnit4 to test my code. Now, I'm aware that the following annotation allows me to expect an exception of a certain type @Test(expected = NipException.class) However, I have an 'errorCode' property in my exception class which I would also like to verify. This is because the same exception is thrown at three places in the same method with different error codes. How do I access 'errorCode' of the thrown exception?

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  • JTree - Issues with adding of nodes

    - by John
    Hi. Im developing a system that stores courses that participants can apply to. I'm presenting the enrollments in a JTree in the courseadministratorGUI. My problem is that, for every enrollment it's adding a new courseNode. Been trying for many hours, and hope I can now get some advice that will point me in the correct direction. Thank you. private void updateJTree() { for (Category cat : catcontrol.getAllCategoriesList()) { category = new DefaultMutableTreeNode(cat); for (Course c : ccontrol.getAllCourses()) { if (cat.getIdCategory() == c.getIdCategory()) { for (Enrollment e : econtrol.getAllEnrollments()) { if (e.getIdCourse() == c.getIdCourse()) { if (cat.getIdCategory() == c.getIdCategory() && e.getCourse().equals(c)) { root.add(category); } if (c.getIdCourse() == e.getIdCourse()) { course = new DefaultMutableTreeNode(c); category.add(course); enrollment = new DefaultMutableTreeNode(e.getParticipant().getFirstNames()); course.add(enrollment); } } } } } } jTree1.setModel(new DefaultTreeModel(root)); jTree1.addTreeSelectionListener(this); jTree1.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION); }

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  • Hibernate: deletes not cascading for self-referencing entities

    - by jwaddell
    I have the following (simplified) Hibernate entities: @Entity @Table(name = "package") public abstract class Package { protected Content content; @ManyToOne(cascade = {javax.persistence.CascadeType.ALL}) @JoinColumn(name = "content_id") @Fetch(value = FetchMode.JOIN) public Content getContent() { return content; } public void setContent(Content content) { this.content = content; } } @Entity @Table(name = "content") public class Content { private Set<Content> subContents = new HashSet<Content>(); @ManyToMany(fetch = FetchType.EAGER) @JoinTable(name = "subcontents", joinColumns = {@JoinColumn(name = "content_id")}, inverseJoinColumns = {@JoinColumn(name = "elt")}) @Cascade(value = {org.hibernate.annotations.CascadeType.DELETE, org.hibernate.annotations.CascadeType.REPLICATE}) @Fetch(value = FetchMode.SUBSELECT) public Set<Content> getSubContents() { return subContents; } public void setSubContents(Set<Content> subContents) { this.subContents = subContents; } } So a Package has a Content, and a Content is self-referencing in that it has many sub-Contents (which may contain sub-Contents of their own etc). The relationships are required to be ManyToOne (Package to Content) and ManyToMany (Content to sub-Contents) but for the case I am currently testing each sub-Content only relates to one Package or Content. The problem is that when I delete a Package and flush the session, I get a Hibernate error stating that I'm violating a foreign key constraint on table subcontents, with a particular content_id still referenced from table subcontents. I've tried specifically (recursively) deleting the Contents before deleting the Package but I get the same error. Is there a reason why this entity tree is not being deleted properly?

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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  • Is there a useDirtyFlag option for Tomcat 6 cluster configuration?

    - by kevinjansz
    In Tomcat 5.0.x you had the ability to set useDirtyFlag="false" to force replication of the session after every request rather than checking for set/removeAttribute calls. <Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster" managerClassName="org.apache.catalina.cluster.session.SimpleTcpReplicationManager" expireSessionsOnShutdown="false" **useDirtyFlag="false"** doClusterLog="true" clusterLogName="clusterLog"> ... The comments in the server.xml stated this may be used to make the following work: <% HashMap map = (HashMap)session.getAttribute("map"); map.put("key","value"); %> i.e. change the state of an object that has already been put in the session and you can be sure that this object still be replicated to the other nodes in the cluster. According to the Tomcat 6 documentation you only have two "Manager" options - DeltaManager & BackupManager ... neither of these seem to allow this option or anything like it. In my testing the default setup: <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> where you get the DeltaManager by default, it's definitely behaving as useDirtyFlag="true" (as I'd expect). So my question is - is there an equivalent in Tomcat 6? Looking at the source I can see a manager implementation "org.apache.catalina.ha.session.SimpleTcpReplicationManager" which does have the useDirtyFlag but the javadoc comments in this state it's "Tomcat Session Replication for Tomcat 4.0" ... I don't know if this is ok to use - I'm guessing not as it's not mentioned in the main cluster configuration documentation.

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  • ExecutionException and InterruptedException while using Future class's get() method

    - by java_geek
    ExecutorService executor = Executors.newSingleThreadExecutor(); try { Task t = new Task(response,inputToPass,pTypes,unit.getInstance(),methodName,unit.getUnitKey()); Future<SCCallOutResponse> fut = executor.submit(t); response = fut.get(unit.getTimeOut(),TimeUnit.MILLISECONDS); } catch (TimeoutException e) { // if the task is still running, a TimeOutException will occur while fut.get() cat.error("Unit " + unit.getUnitKey() + " Timed Out"); response.setVote(SCCallOutConsts.TIMEOUT); } catch (InterruptedException e) { cat.error(e); } catch (ExecutionException e) { cat.error(e); } finally { executor.shutdown(); } } How should i handle the InterruptedException and ExecutionException in the code? And in what cases are these exceptions thrown?

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  • Why does the BigFraction class in the Apache-Commons-Math library return incorrect division results?

    - by Timothy Lee Russell
    In the spirit of using existing, tested and stable libraries of code, I started using the Apache-Commons-Math library and its BigFraction class to perform some rational calculations for an Android app I'm writing called RationalCalc. It works great for every task that I have thrown at it, except for one nagging problem. When dividing certain BigFraction values, I am getting incorrect results. If I create a BigFraction with the inverse of the divisor and multiply instead, I get the same incorrect answer but perhaps that is what the library is doing internally anyway. Does anyone know what I am doing wrong? The division works correctly with a BigFraction of 2.5 but not 2.51, 2.49, etc... // *** incorrect! *** BigFraction one = new BigFraction(1.524); //one: 1715871458028159 / 1125899906842624 BigFraction two = new BigFraction(2.51); //two: 1413004383087493 / 562949953421312 BigFraction three = one.divide(two); //three: 0 Log.i("solve", three.toString()); //should be 0.607171315 ?? //returns 0 // *** correct! **** BigFraction four = new BigFraction(1.524); //four: 1715871458028159 / 1125899906842624 BigFraction five = new BigFraction(2.5); //five: 5 / 2 BigFraction six = four.divide(five); //six: 1715871458028159 / 2814749767106560 Log.i("solve", six.toString()); //should be 0.6096 ?? //returns 0.6096

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  • Swingbuilder - application location centering

    - by Amoeba
    I am creating an application using Griffon-SwingBuilder. I would like to able to center the application on the desktop. I know we have the 'location: [x,y]' argument we can provide on application creation. Is there anyway to access desktop properties to calculate the center?

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  • Counting down to zero in contrast to counting up to length - 1

    - by Helper Method
    Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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  • Using collections/containers/catalogs in Domain Models

    - by devoured elysium
    Let's say I want to model a cinema. The cinema will have a couple of rooms(for example, 7), where the movies are being played. I wonder how should I design the domain model for this scenario. Should the Cinema class concept concept have a direct association with the 7 rooms? Should the Cinema class concept have an association with a catalog of the 7 rooms? Why? I am having some trouble understanding why in some places I see the first case and in some others I see something like the second case. If instead of rooms, I wanted to depict the relationship between Cinema and: Tickets to sell (today). Tickets already sold (today) Customers in the Cinema database The set of hours at which there are movies playing in a given room in the cinema. The set of places you can sit at in a room in the cinema. Should I use catalogs, should I connect them directly to the Cinema concept with a multiplicity of * in the target? Thanks

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  • Is it better to use List or Collection?

    - by Vivin Paliath
    I have an object that stores some data in a list. The implementation could change later, and I don't want to expose the internal implementation to the end user. However, the user must have the ability to modify and access this collection of data. Currently I have something like this: public List<SomeDataType> getData() { return this.data; } public void setData(List<SomeDataType> data) { this.data = data; } Does this mean that I have allowed the internal implementation details to leak out? Should I be doing this instead? public Collection<SomeDataType> getData() { return this.data; } public void setData(Collection<SomeDataType> data) { this.data = new ArrayList<SomeDataType>(data); }

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  • Detecting client disconnect in tomcat servlet?

    - by Seth
    How can I detect that the client side of a tomcat servlet request has disconnected? I've read that I should do a response.getOutputStream().print(), then a response.getOutputStream().flush() and catch an IOException, but is there a way I can detect this without writing any data?

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