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  • Hibernate Query for a List of Objects that matches a List of Objects' ids

    - by sal
    Given a classes Foo, Bar which have hibernate mappings to tables Foo, A, B and C public class Foo { Integer aid; Integer bid; Integer cid; ...; } public class Bar { A a; B b; C c; ...; } I build a List fooList of an arbitrary size and I would like to use hibernate to fetch List where the resulting list will look something like this: Bar[1] = [X1,Y2,ZA,...] Bar[2] = [X1,Y2,ZB,...] Bar[3] = [X1,Y2,ZC,...] Bar[4] = [X1,Y3,ZD,...] Bar[5] = [X2,Y4,ZE,...] Bar[6] = [X2,Y4,ZF,...] Bar[7] = [X2,Y5,ZG,...] Bar[8] = ... Where each Xi, Yi and Zi represents a unique object. I know I can iterate fooList and fetch each List and call barList.addAll(...) to build the result list with something like this: List<bar> barList.addAll(s.createQuery("from Bar bar where bar.aid = :aid and ... ") .setEntity("aid", foo.getAid()) .setEntity("bid", foo.getBid()) .setEntity("cid", foo.getCid()) .list(); ); Is there any easier way, ideally one that makes better use of hibernate and make a minimal number of database calls? Am I missing something? Is hibernate not the right tool for this?

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  • Handling multiple exceptions

    - by the-banana-king
    Hi there, I have written a class which loads configuration objects of my application and keeps track of them so that I can easily write out changes or reload the whole configuration at once with a single method call. However, each configuration object might potentially throw an exception when doing IO, yet I do not want those errors to cancel the overall process so that the other objects are still given a chance to reload/write. Therefore I collect all exceptions which are thrown while iterating over the objects and store them in a super-exception, which is thrown after the loop, since each exception must still be handled and someone has to be notified of what exactly went wrong. However, that approach looks a bit odd to me. Someone out there with a cleaner solution? Here is some code of the mentioned class: public synchronized void store() throws MultipleCauseException { MultipleCauseException me = new MultipleCauseException("unable to store some resources"); for(Resource resource : this.resources.values()) { try { resource.store(); } catch(StoreException e) { me.addCause(e); } } if(me.hasCauses()) throw me; }

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  • translating specifications into query predicates

    - by Jeroen
    I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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  • Need help with writing test

    - by London
    I'm trying to write a test for this class its called Receiver : public void get(People person) { if(null != person) { LOG.info("Person with ID " + person.getId() + " received"); processor.process(person); }else{ LOG.info("Person not received abort!"); } } Here is the test : @Test public void testReceivePerson(){ context.checking(new Expectations() {{ receiver.get(person); atLeast(1).of(person).getId(); will(returnValue(String.class)); }}); } Note: receiver is the instance of Receiver class(real not mock), processor is the instance of Processor class(real not mock) which processes the person(mock object of People class). GetId is a String not int method that is not mistake. Test fails : unexpected invocation of person.getId() I'm using jMock any help would be appreciated. As I understood when I call this get method to execute it properly I need to mock person.getId() , and I've been sniping around in circles for a while now any help would be appreciated.

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  • Use continue or Checked Exceptions when checking and processing objects

    - by Johan Pelgrim
    I'm processing, let's say a list of "Document" objects. Before I record the processing of the document successful I first want to check a couple of things. Let's say, the file referring to the document should be present and something in the document should be present. Just two simple checks for the example but think about 8 more checks before I have successfully processed my document. What would have your preference? for (Document document : List<Document> documents) { if (!fileIsPresent(document)) { doSomethingWithThisResult("File is not present"); continue; } if (!isSomethingInTheDocumentPresent(document)) { doSomethingWithThisResult("Something is not in the document"); continue; } doSomethingWithTheSucces(); } Or for (Document document : List<Document> documents) { try { fileIsPresent(document); isSomethingInTheDocumentPresent(document); doSomethingWithTheSucces(); } catch (ProcessingException e) { doSomethingWithTheExceptionalCase(e.getMessage()); } } public boolean fileIsPresent(Document document) throws ProcessingException { ... throw new ProcessingException("File is not present"); } public boolean isSomethingInTheDocumentPresent(Document document) throws ProcessingException { ... throw new ProcessingException("Something is not in the document"); } What is more readable. What is best? Is there even a better approach of doing this (maybe using a design pattern of some sort)? As far as readability goes my preference currently is the Exception variant... What is yours?

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  • Saving tree-structures in Databases

    - by Nina Null
    Hello everyone. I use Hibernate/Spring and a MySQL Database for my data management. Currently I display a tree-structure in a JTable. A tree can have several branches, in turn a branch can have several branches (up to nine levels) again, or having leaves. Lately I have performanceproblemes, as soon as I want to create new branches on deeper levels. At this time a branch has a foreign key to its parent. The domainobject has access to its parent by calling getParent(), which returns the parent-branch. The deeper the level, the longer it takes to create a new branch. Microbenchmark results for creating a new branch are like: Level 1: 32 ms. Level 3: 80 ms. Level 9: 232 ms. Obviously the level (which means the number of parents) is responsible for this. So I wanted to ask, if there are any appendages to work around this kind of problem. I don’t understand why Hibernate needs to know about the whole object tree (all parents until the root) while creating a new branch. But as far as I know this can be the only reason for the delay while creating a new branch, because a branch doesn’t have any other relations to any other objects. I would be very thankful for any workarounds or suggestions. greets, jambusa

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  • Is using the break statement bad practice?

    - by Lchi
    I've been told by professors and peers at my university that using the break statement is bad practice, but through my coursework haven't come up with a great reason why. Those who claim that it is bad say that it's a "get out of jail free card" and that you can always avoid using it. My guesses for why its considered bad would be that you could possibly skip some cleanup code after the break, or similarly exit some control structure in an inconsistent state. Is there any reason why using break is(n't) bad practice?

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  • Encountering NullPointerException when trying to add polynoms

    - by Ayler Cruz
    I need to add two polynomials, which is composed of two ints. For example, the coefficient and the exponent 3x^2 would be constructed using 3 and 2 as parameters. I am getting a NullPointerException but I can't figure out why. Any help would be appreciated! public class Polynomial { private Node poly; public Polynomial() { } private Polynomial(Node p) { poly = p; } private class Term { int coefficient; int exponent; private Term(int coefficient, int exponent) { this.coefficient = coefficient; this.exponent = exponent; } } private class Node { private Term data; private Node next; private Node(Term data, Node next) { this.data = data; this.next = next; } } public void addTerm(int coeff, int exp) { Node pointer = poly; if (pointer.next == null) { poly.next = new Node(new Term(coeff, exp), null); } else { while (pointer.next != null) { if (pointer.next.data.exponent < exp) { Node temp = new Node(new Term(coeff, exp), pointer.next.next); pointer.next = temp; return; } pointer = pointer.next; } pointer.next = new Node(new Term(coeff, exp), null); } } public Polynomial polyAdd(Polynomial p) { return new Polynomial(polyAdd(this.poly, p.poly)); } private Node polyAdd(Node p1, Node p2) { if (p1 == p2) { Term adding = new Term(p1.data.coefficient + p2.data.coefficient, p1.data.exponent); p1 = p1.next; p2 = p2.next; return new Node(adding, null); } if (p1.data.exponent > p2.data.exponent) { p2 = p2.next; } if (p1.data.exponent < p2.data.exponent) { p1 = p1.next; } if (p1.next != null && p2.next != null) { return polyAdd(p1, p2); } return new Node(null, null); } }

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  • Graphing the pitch (frequency) of a sound

    - by Coronatus
    I want to plot the pitch of a sound into a graph. Currently I can plot the amplitude. The graph below is created by the data returned by getUnscaledAmplitude(): AudioInputStream audioInputStream = AudioSystem.getAudioInputStream(new BufferedInputStream(new FileInputStream(file))); byte[] bytes = new byte[(int) (audioInputStream.getFrameLength()) * (audioInputStream.getFormat().getFrameSize())]; audioInputStream.read(bytes); // Get amplitude values for each audio channel in an array. graphData = type.getUnscaledAmplitude(bytes, this); public int[][] getUnscaledAmplitude(byte[] eightBitByteArray, AudioInfo audioInfo) { int[][] toReturn = new int[audioInfo.getNumberOfChannels()][eightBitByteArray.length / (2 * audioInfo. getNumberOfChannels())]; int index = 0; for (int audioByte = 0; audioByte < eightBitByteArray.length;) { for (int channel = 0; channel < audioInfo.getNumberOfChannels(); channel++) { // Do the byte to sample conversion. int low = (int) eightBitByteArray[audioByte]; audioByte++; int high = (int) eightBitByteArray[audioByte]; audioByte++; int sample = (high << 8) + (low & 0x00ff); if (sample < audioInfo.sampleMin) { audioInfo.sampleMin = sample; } else if (sample > audioInfo.sampleMax) { audioInfo.sampleMax = sample; } toReturn[channel][index] = sample; } index++; } return toReturn; } But I need to show the audio's pitch, not amplitude. Fast Fourier transform appears to get the pitch, but it needs to know more variables than the raw bytes I have, and is very complex and mathematical. Is there a way I can do this?

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  • Relation many-to-many with attributes : how ?

    - by mada
    Hi, Excuse me for my poor english in advance as it is not my mother tongue. Like in this example: http://www.xylax.net/hibernate/manytomany.html But i have in the table foo-bar 2 attributes which are not part of the primary or foreign keys.: one boolean(A) & one string(B). I know how to map it without attributes but not in this case. I have not found an answer in the documentation. I need to know please how to map it & what kind of collection i have to declare in my class Foo. Thanks in advance for your answer. I really appreciate the time given by you.

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  • Avoid having a huge collection of ids by calling a DAO.getAll()

    - by Michael Bavin
    Instead of returning a List<Long> of ids when calling PersonDao.getAll() we wanted not to have an entire collection of ids in memory. Seems like returning a org.springframework.jdbc.support.rowset.SqlRowSet and iterate over this rowset would not hold every object in memory. The only problem here is i cannot cast this row to my entity. Is there a better way for this?

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  • Resizing a GLJPanel with JOGL causes my model to disappear.

    - by badcodenotreat
    I switched over to using a GLJPanel from a GLCanvas to avoid certain flickering issues, however this has created several unintended consequences of it's own. From what I've gleaned so far, GLJPanel calls GLEventListener.init() every time it's resized which either resets various openGL functions i've enabled in init() (depth test, lighting, etc...) if i'm lucky, or completely obliterates my model if i'm not. I've tried debugging it but I'm not able to correct this behavior. This is my init() function: gl.glShadeModel( GL.GL_SMOOTH ); gl.glEnable( GL.GL_DEPTH_TEST ); gl.glDepthFunc( GL.GL_LEQUAL ); gl.glDepthRange( zNear, zFar ); gl.glDisable( GL.GL_LINE_SMOOTH ); gl.glEnable(GL.GL_NORMALIZE); gl.glEnable( GL.GL_BLEND ); gl.glBlendFunc( GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA ); // set up the background color gl.glClearColor( ((float)backColor.getRed () / 255.0f), ((float)backColor.getGreen() / 255.0f), ((float)backColor.getBlue () / 255.0f), 1.0f); gl.glEnable ( GL.GL_LIGHTING ); gl.glLightfv( GL.GL_LIGHT0, GL.GL_AMBIENT, Constants.AMBIENT_LIGHT, 0 ); gl.glLightfv( GL.GL_LIGHT0, GL.GL_DIFFUSE, Constants.DIFFUSE_LIGHT, 0 ); gl.glEnable ( GL.GL_LIGHT0 ); gl.glTexEnvf( GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, GL.GL_MODULATE ); gl.glHint( GL.GL_PERSPECTIVE_CORRECTION_HINT, GL.GL_NICEST ); // code to generate model Is there any way around this other than removing everything from init(), adding it to my display() function? Given the behavior of init() and reshape() for GLJPanel, i'm not sure if that will fix it either.

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  • Remove duplicates from a list

    - by Mercer
    Hello i want to remove duplicates from a list i do this but not working List<Customer> listCustomer = new ArrayList<Customer>(); for (Customer customer: tmpListCustomer) { if (!listCustomer.contains(customer)) { listCustomer.add(customer); } }

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  • Combobox having values but not showing text

    - by ras
    hi, I'm using GWT-EXT combobox. My problem is when I render the combobox, it's having as many rows as it has values but all the rows are empty means text is not shown. Here's my code. Combobox cb = new Combobox(); cb.setForceSelection(true); cb.setMinChars(1); cb.setWidth(200); cb.setStore(store); // Store is perfectly loaded in combobox cb.setDisplayField("ReportName"); cb.setMode(ComboBox.LOCAL); cb.setTriggerAction(ALL); cb.setEmptyText("--Select--"); cb.setLoadingText("Searching..."); cb.setTypeAhead(true); cb.setSelectOnFocus(true); All other code is working fine. I'm sure for one thing that this problem is related to one of the functions of Combobox. Thanks in advance.

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  • Migrating from hand-written persistence layer to ORM

    - by Sergey Mikhanov
    Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

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  • OutOfMemoryError during the pdf merge

    - by Vijay
    the below code merges the pdf files and returns the combined pdf data. while this code runs, i try to combine the 100 files with each file approximately around 500kb, i get outofmemory error in the line document.close();. this code runs in the web environment, is the memory available to webspehere server is the problem? i read in an article to use freeReader method, but i cannot get how to use it my scenario. protected ByteArrayOutputStream joinPDFs(List<InputStream> pdfStreams, boolean paginate) { Document document = new Document(); ByteArrayOutputStream mergedPdfStream = new ByteArrayOutputStream(); try { //List<InputStream> pdfs = pdfStreams; List<PdfReader> readers = new ArrayList<PdfReader>(); int totalPages = 0; //Iterator<InputStream> iteratorPDFs = pdfs.iterator(); Iterator<InputStream> iteratorPDFs = pdfStreams.iterator(); // Create Readers for the pdfs. while (iteratorPDFs.hasNext()) { InputStream pdf = iteratorPDFs.next(); if (pdf == null) continue; PdfReader pdfReader = new PdfReader(pdf); readers.add(pdfReader); totalPages += pdfReader.getNumberOfPages(); } //clear this pdfStreams = null; //WeakReference ref = new WeakReference(pdfs); //ref.clear(); // Create a writer for the outputstream PdfWriter writer = PdfWriter.getInstance(document, mergedPdfStream); writer.setFullCompression(); document.open(); BaseFont bf = BaseFont.createFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED); PdfContentByte cb = writer.getDirectContent(); // Holds the PDF // data PdfImportedPage page; int currentPageNumber = 0; int pageOfCurrentReaderPDF = 0; Iterator<PdfReader> iteratorPDFReader = readers.iterator(); // Loop through the PDF files and add to the output. while (iteratorPDFReader.hasNext()) { PdfReader pdfReader = iteratorPDFReader.next(); // Create a new page in the target for each source page. while (pageOfCurrentReaderPDF < pdfReader.getNumberOfPages()) { pageOfCurrentReaderPDF++; document.setPageSize(pdfReader .getPageSizeWithRotation(pageOfCurrentReaderPDF)); document.newPage(); // pageOfCurrentReaderPDF++; currentPageNumber++; page = writer.getImportedPage(pdfReader, pageOfCurrentReaderPDF); cb.addTemplate(page, 0, 0); // Code for pagination. if (paginate) { cb.beginText(); cb.setFontAndSize(bf, 9); cb.showTextAligned(PdfContentByte.ALIGN_CENTER, "" + currentPageNumber + " of " + totalPages, 520, 5, 0); cb.endText(); } } pageOfCurrentReaderPDF = 0; System.out.println("now the size is: "+pdfReader.getFileLength()); } mergedPdfStream.flush(); document.close(); mergedPdfStream.close(); return mergedPdfStream; } catch (Exception e) { e.printStackTrace(); } finally { if (document.isOpen()) document.close(); try { if (mergedPdfStream != null) mergedPdfStream.close(); } catch (IOException ioe) { ioe.printStackTrace(); } } return mergedPdfStream; } Thanks V

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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • getPackage() returning null when my JUnit test is run from Ant

    - by philharvey
    I'm having problems running a JUnit test. It runs fine in Eclipse, but now I'm trying to run it from the command-line using Ant. The problem is that the following code is returning null: getClass().getPackage(). I'm running my JUnit test like so: <junit fork="no" printsummary="yes" haltonfailure="no"> <classpath refid="junit.classpath" /> <batchtest fork="yes" todir="${reports.junit}"> <fileset dir="${junit.classdir}"> <include name="**/FileHttpServerTest.class" /> <exclude name="**/*$*" /> </fileset> </batchtest> <formatter type="xml" /> ... I Googled for this sort of error, and found a number of references to classloader misbehaviour. But I've found nothing gave me enough information to solve my problem. I really need getClass().getPackage() to not return null. Can anyone help me? Thanks, Phil

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  • Why is JavaMail Transport.send() a static method?

    - by skiphoppy
    I'm revising code I did not write that uses JavaMail, and having a little trouble understanding why the JavaMail API is designed the way it is. I have the feeling that if I understood, I could be doing a better job. We call: transport = session.getTransport("smtp"); transport.connect(hostName, port, user, password); So why is Eclipse warning me that this: transport.send(message, message.getAllRecipients()); is a call to a static method? Why am I getting a Transport object and providing settings that are specific to it if I can't use that object to send the message? How does the Transport class even know what server and other settings to use to send the message? It's working fine, which is hard to believe. What if I had instantiated Transport objects for two different servers; how would it know which one to use? In the course of writing this question, I've discovered that I should really be calling: transport.sendMessage(message, message.getAllRecipients()); So what is the purpose of the static Transport.send() method? Is this just poor design, or is there a reason it is this way?

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  • Eclipse 3.5: Implementing my own context menu for a MultipageEditorPart --> no viewer involved

    - by Patrick
    Hello! :-) In my current RCP-project i use a MultipageEditorPart. It has various pages, with simple SWT composites on it. The composites contain some Text and Combo elements. When the user right clicks onto the editor page, I want a context menu to open. This menu holds a command for creating a new editor page, with a composite on it. The command is already working, but I'm quite clueless about how to implement the context menu for the editor. Can someone help with this?

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  • setting user.dir system property in JBoss 5.1

    - by Spiderman
    In JBoss 4.2.3 the System property 'user.dir' is defined to be <JBoss-root>/bin when I ran the same application on JBoss 5.1 I noticed that it cannot find the System property user.dir why there is no default definition for version 5.1? and how can I define it manually? I followed this suggestion and added my property into properties-service.xml but it had no affect and still JBoss couldn't find the system:user.dir value.

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