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  • Validate XSD with XML .

    - by munish
    I want to know how to validate XML with XSD . XML is not of an element type but a complex type . Since validator class's validate method compare only element type. So basically I want to valide XSD's complex type with an XML. e.g. Basic XSD below xs:element name="Customer"> <xs:complexType> <xs:sequence> <xs:element name="Dob" type="xs:date" /> <xs:element name="Address"> <xs:complexType> <xs:sequence> <xs:element name="Line1" type="xs:string" /> <xs:element name="Line2" type="xs:string" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> We can assume we have multiple complex type in the Customer element. MY XML is <Address> <Line1>34 thingy street, someplace</Line1> <Line2>sometown, w1w8uu </Line2> </Address> How I validate my XML with XSD. Kindly post your suggestions in java

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  • Detecting Singularities in a Graph

    - by nasufara
    I am creating a graphing calculator in Java as a project for my programming class. There are two main components to this calculator: the graph itself, which draws the line(s), and the equation evaluator, which takes in an equation as a String and... well, evaluates it. To create the line, I create a Path2D.Double instance, and loop through the points on the line. To do this, I calculate as many points as the graph is wide (e.g. if the graph itself is 500px wide, I calculate 500 points), and then scale it to the window of the graph. Now, this works perfectly for most any line. However, it does not when dealing with singularities. If, when calculating points, the graph encounters a domain error (such as 1/0), the graph closes the shape in the Path2D.Double instance and starts a new line, so that the line looks mathematically correct. Example: However, because of the way it scales, sometimes it is rendered correctly, sometimes it isn't. When it isn't, the actual asymptotic line is shown, because within those 500 points, it skipped over x = 2.0 in the equation 1 / (x-2), and only did x = 1.98 and x = 2.04, which are perfectly valid in that equation. Example: In that case, I increased the window on the left and right one unit each. My question is: Is there a way to deal with singularities using this method of scaling so that the resulting line looks mathematically correct? I myself have thought of implementing a binary search-esque method, where, if it finds that it calculates one point, and then the next point is wildly far away from the last point, it searches in between those points for a domain error. I had trouble figuring out how to make it work in practice, however. Thank you for any help you may give!

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  • casting Collection<SomeClass> to Collection<SomeSuperClass>

    - by skrebbel
    Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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  • Turning a JSON list into a POJO

    - by Josh L
    I'm having trouble getting this bit of JSON into a POJO. I'm using Jackson configured like this: protected ThreadLocal<ObjectMapper> jparser = new ThreadLocal<ObjectMapper>(); public void receive(Object object) { try { if (object instanceof String && ((String)object).length() != 0) { ObjectDefinition t = null ; if (parserChoice==0) { if (jparser.get()==null) { jparser.set(new ObjectMapper()); } t = jparser.get().readValue((String)object, ObjectDefinition.class); } Object key = t.getKey(); if (key == null) return; transaction.put(key,t); } } catch (Exception e) { e.printStackTrace(); } } Here's the JSON that needs to be turned into a POJO: { "id":"exampleID1", "entities":{ "tags":[ { "text":"textexample1", "indices":[ 2, 14 ] }, { "text":"textexample2", "indices":[ 31, 36 ] }, { "text":"textexample3", "indices":[ 37, 43 ] } ] } And lastly, here's what I currently have for the java class: protected Entities entities; @JsonIgnoreProperties(ignoreUnknown = true) protected class Entities { public Entities() {} protected Tags tags; @JsonIgnoreProperties(ignoreUnknown = true) protected class Tags { public Tags() {} protected String text; public String getText() { return text; } public void setText(String text) { this.text = text; } }; public Tags getTags() { return tags; } public void setTags(Tags tags) { this.tags = tags; } }; //Getters & Setters ... I've been able to translate the more simple objects into a POJO, but the list has me stumped. Any help is appreciated. Thanks!

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  • Illegal Argument Exception in Google Wave App

    - by Yoenhofen
    I'm writing a Google Wave robot and I just messed something up. It was working just fine but now I'm getting an IllegalArgument exception on the line that includes query.execute. Am I doing something stupid? I've seen several code samples very similar to what I'm doing. I can include the code of the WaveUpdate class if necessary. The intent here is to select all WaveUpdate members that have an updateDateTime in the last hour. PersistenceManager pm = PMF.get().getPersistenceManager(); try { Query query = pm.newQuery(WaveUpdate.class); query.setFilter("emailAddress > '' && updateDateTime > referenceDateTime"); query.declareParameters("java.util.Date referenceDateTime"); Calendar referenceDateTime = Calendar.getInstance(); referenceDateTime.add(Calendar.HOUR_OF_DAY, -1); List<WaveUpdate> updates = (List<WaveUpdate>) query.execute(referenceDateTime.getTime());

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  • JSESSIONID collision between two servers on same ip but different ports

    - by Steve Armstrong
    I've got a situation where I have two different webapps running on a single server, using different ports. They're both running Java's Jetty servlet container, so they both use a cookie parameter named JSESSIONID to track the session id. These two webapps are fighting over the session id. Open a Firefox tab, and go to WebApp1 WebApp1's HTTP response has a set-cookie header with JSESSIONID=1 Firefox now has a Cookie header with JSESSIONID=1 in all it's HTTP requests to WebApp1 Open a second Firefox tab, and go to WebApp2 The HTTP reqeust to WebApp2 also has a Cookie header with JSESSIONID=1, but in the doGet, when I call req.getSession(false); I get null. And if I call req.getSession(true) I get a new Session object, but then the HTTP response from WebApp2 has a set-cookie header with JSESSIONID=20 Now, WebApp2 has a working Session, but WebApp1's session is gone. Going to WebApp1 will give me a new session, blowing away WebApp2's session. Continue forever So the Sessions are thrashing between each web app. I'd really like for the req.getSession(false) to return a valid session if there's already a JSESSIONID cookie defined. One option is to basically reimplement the Session framework with a HashMap and cookies called WEBAPP1SESSIONID and WEBAPP2SESSIONID, but that sucks, and means I'll have to hack the new Session stuff into ActionServlet and a few other places. This must be a problem others have encountered. Is Jetty's HttpServletRequest.getSession(boolean) just crappy?

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  • JAAS + authentification from database

    - by AhmedDrira
    i am traying to performe an authentification from data base using JAAS i v configured the login-config.xml like this <application-policy name="e-procurment_domaine"> <authentication> <login-module code="org.jboss.security.auth.spi.DatabaseServerLoginModule" flag="required"> <module-option name = "dsJndiName">BasepfeDS</module-option> <module-option name="securityDomain">java:/jaas/e-procurment_domaine</module-option> <module-option name="principalsQuery">SELECT pass FROM personne WHERE login=?</module-option> <module-option name="rolesQuery">SELECT disc FROM personne WHERE login=?</module-option> </login-module> </authentication> </application-policy> and I've written a test : this one @Test public void testFindALL() { System.out.println("Debut test de la méthode findALL"); // WebAuthentication wa=new WebAuthentication(); // wa.login("zahrat", "zahrat"); securityClient.setSimple("zahrat", "zahrat"); try { securityClient.login(); } catch (LoginException e) { // TODO Auto-generated catch block e.printStackTrace(); } Acheteur acheteur = new Acheteur(); System.out.println("" + acheteurRemote.findAll().size()); // } catch (EJBAccessException ex) { // System.out.println("Erreur attendue de type EJBAccessException: " // + ex.getMessage()); // } catch (Exception ex) { // ex.printStackTrace(); // fail("Exception pendant le test find ALL"); System.out.println("Fin test find ALL");} // } the test is fail i dont know why , but when i change the polycy with the methode of .property file it works .. i am using the annotation on the session BEAN classes @SecurityDomain("e-procurment_domaine") @DeclareRoles({"acheteur","vendeur","physique"}) @RolesAllowed({"acheteur","vendeur","physique"}) and the annotation on the session for the methode @RolesAllowed("physique") @Override public List<Acheteur> findAll() { log.debug("fetching all Acheteur"); return daoGenerique.findWithNamedQuery("Acheteur.findAll"); } i think that the test have an acess to my data base doe's it need mysql DRIVER or a special config on JBOSS?

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  • Copy a directory from a jar file

    - by Macarse
    Hi. I recently finished and application and created a jar file. One of my classes creates an output directory populating it with files from it's resource. The code is something like this: // Copy files from dir "template" in this class resource to output. private void createOutput(File output) throws IOException { File template = new File(FileHelper.URL2Path(getClass().getResource("template"))); FileHelper.copyDirectory(template, output); } The problem is that now that I am running for a jar, this doesn't work. I tried without luck: Using Streams to solve similar stuff on other classes but it doesn't work with dirs. Code was similar to http://www.exampledepot.com/egs/java.io/CopyFile.html Creating the File template with new File(getClass().getResource("template").toUri()) While writting this I was thinking about instead of having a template dir in the resource path having a zip file of it. Doing it this way I could get the file as an inputStream and unzip it where I need to. But I am not sure if it's the correct way. Thanks for reading!

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  • facebook: why I can't send email from app to user?

    - by flybywire
    I can't send email to my app users, even though I have the permissions. I am working with the java library, although I don't think it is related to that. long uid = ...; Collection<Long> uids = new ArrayList<Long>(); uids.add(uid); FacebookXmlRestClient client = new FacebookXmlRestClient(api, secret); boolean sendEmailPerm = client.users_hasAppPermission(Permission.EMAIL,uid); System.out.println("Can send email: "+ sendEmailPerm); Collection<String> sent = client.notifications_sendTextEmail(uids, "subject", "body"); System.out.println("Succesfully sent email to: "+sent); sent = client.notifications_sendFbmlEmail(uids, "subject", "body"); System.out.println("Succesfully sent email to: "+sent); I am trying both with fbml and text email. I can also obtain the user's proxied_email property but when I send email to that address with my regular mail client is doesn't arrive. The output is: Can send email: true Succesfully sent email to: [] Succesfully sent email to: []

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  • I want to read program content from command line.

    - by Alexandre Dominos
    I am trying to update a program which was wrotten in 1995 with pascal or c. I am not sure about programming language. Command line program. Now I am coded in C#. And I want to read program command line content. Is it possible? I tried something. But not succesfull. They are: private void aboutToolStripMenuItem_Click(object sender, EventArgs e) { // Redirect the output stream of the child process. p.StartInfo.UseShellExecute = false; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.FileName = "osl.exe"; p.Start(); logs.AppendText("Timer Started\n"); timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) { // write somethingg and read what is the program doing on command line? // What is the program printint? etc... // I try this code but not enough for mo. // logs.AppendText("d:" + p.StandardOutput.ReadToEnd()+"\n"); } private void p_Exited(object sender, EventArgs e) { timer1.Enabled = false; } i am open to any idea in java,cpp,c,c#.

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  • GC output clarification

    - by elec
    I'm running a java application with the following settings: -XX:+CMSParallelRemarkEnabled -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution I'm not sure how to interpret the related gc logs(below). In particular: Heap after GC invocations=31 (full 3): does this mean there were 31 minor GCs, and 3 full GCs ? What triggers the several consecutive lines of Total time for which the application threads were stopped and Application Time ? Is it possible to get the time stamps associated with each of these lines ? GC logs: Total time for which application threads were stopped: 0.0046910 seconds Application time: 0.7946670 seconds Total time for which application threads were stopped: 0.0002900 seconds Application time: 1.0153640 seconds Total time for which application threads were stopped: 0.0002780 seconds Application time: 1.0161890 seconds Total time for which application threads were stopped: 0.0002760 seconds Application time: 1.0145990 seconds Total time for which application threads were stopped: 0.0002950 seconds Application time: 0.9999800 seconds Total time for which application threads were stopped: 0.0002770 seconds Application time: 1.0151640 seconds Total time for which application threads were stopped: 0.0002730 seconds Application time: 0.9996590 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 0.9624290 seconds {Heap before GC invocations=30 (full 3): par new generation total 131008K, used 130944K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 100% used [0x00000000eac00000, 0x00000000f2be0000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) to space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) concurrent mark-sweep generation total 131072K, used 48348K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) 2010-05-11T09:30:13.888+0100: 384.955: [GC 384.955: [ParNew Desired survivor size 32768 bytes, new threshold 0 (max 0) : 130944K-0K(131008K), 0.0052470 secs] 179292K-48549K(262080K), 0.0053030 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] Heap after GC invocations=31 (full 3): par new generation total 131008K, used 0K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 0% used [0x00000000eac00000, 0x00000000eac00000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) to space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) concurrent mark-sweep generation total 131072K, used 48549K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) } Total time for which application threads were stopped: 0.0056410 seconds Application time: 0.0475220 seconds Total time for which application threads were stopped: 0.0001800 seconds Application time: 1.0174830 seconds Total time for which application threads were stopped: 0.0003820 seconds Application time: 1.0126350 seconds Total time for which application threads were stopped: 0.0002750 seconds Application time: 1.0155910 seconds Total time for which application threads were stopped: 0.0002680 seconds Application time: 1.0155580 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 1.0155480 seconds Total time for which application threads were stopped: 0.0002970 seconds Application time: 0.9896810 seconds

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  • Hibernate - Problem in parsing mapping file (.hbm.xml)

    - by Yatendra Goel
    I am new to Hibernate. I have an exception while running an Hibernate-based application. The exception is as follows: 16 [main] INFO org.hibernate.cfg.Environment - Hibernate 3.3.2.GA 16 [main] INFO org.hibernate.cfg.Environment - hibernate.properties not found 16 [main] INFO org.hibernate.cfg.Environment - Bytecode provider name : javassist 31 [main] INFO org.hibernate.cfg.Environment - using JDK 1.4 java.sql.Timestamp handling 94 [main] INFO org.hibernate.cfg.Configuration - configuring from resource: /hibernate.cfg.xml 94 [main] INFO org.hibernate.cfg.Configuration - Configuration resource: /hibernate.cfg.xml 219 [main] INFO org.hibernate.cfg.Configuration - Reading mappings from resource : app/data/City.hbm.xml 266 [main] ERROR org.hibernate.util.XMLHelper - Error parsing XML: XML InputStream(12) Attribute "coloumn" must be declared for element type "property". 266 [main] ERROR org.hibernate.util.XMLHelper - Error parsing XML: XML InputStream(13) Attribute "coloumn" must be declared for element type "property". 266 [main] ERROR org.hibernate.util.XMLHelper - Error parsing XML: XML InputStream(14) Attribute "coloumn" must be declared for element type "property". It seems that it is not finding coloumn attribute of the property element in the mappings file but my mappings file do have the coloumn attribute. Below is the mappings file (City.hbm.xml) <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="app.data"> <class name="City" table="CITY"> <id column="CITY_ID" name="cityId"> <generator class="native"/> </id> <property name="cityDisplyaName" coloumn="CITY_DISPLAY_NAME" /> <property coloumn="CITY_MEANINGFUL_NAME" name="cityMeaningFulName" /> <property coloumn="CITY_URL" name="cityURL" /> </class> </hibernate-mapping>

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  • Is a GWT app running on Google App Engine protected from CSRF

    - by gerdemb
    I'm developing a GWT app running on the Google App Engine and wondering if I need to worry about Cross-site request forgery or is that automatically taken care of for me? For every RPC request that requires authentication, I have the following code: public class BookServiceImpl extends RemoteServiceServlet implements BookService { public void deleteInventory(Key<Inventory> inventoryKey) throws NotLoggedInException, InvalidStateException, NotFoundException { DAO dao = new DAO(); // This will throw NotLoggedInException if user is not logged in User user = dao.getCurrentUser(); // Do deletion here } } public final class DAO extends DAOBase { public User getCurrentUser() throws NotLoggedInException { currentUser = UserServiceFactory.getUserService().getCurrentUser(); if(currentUser == null) { throw new NotLoggedInException(); } return currentUser; } I couldn't find any documentation on how the UserService checks authentication. Is it enough to rely on the code above or do I need to to more? I'm a beginner at this, but from what I understand to avoid CSRF attacks some of the strategies are: adding an authentication token in the request payload instead of just checking a cookie checking the HTTP Referer header I can see that I have cookies set from Google with what look like SID values, but I can't tell from the serialized Java objects in the payloads if tokens are being passed or not. I also don't know if the Referer header is being used or not. So, am I worrying about a non-issue? If not, what is the best strategy here? This is a common enough problem, that there must be standard solutions out there...

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  • Is it possible to order by a composite key with JPA and CriteriaBuilder

    - by Kjir
    I would like to create a query using the JPA CriteriaBuilder and I would like to add an ORDER BY clause. This is my entity: @Entity @Table(name = "brands") public class Brand implements Serializable { public enum OwnModeType { OWNER, LICENCED } @EmbeddedId private IdBrand id; private String code; //bunch of other properties } Embedded class is: @Embeddable public class IdBrand implements Serializable { @ManyToOne private Edition edition; private String name; } And the way I am building my query is like this: CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<Brand> q = cb.createQuery(Brand.class).distinct(true); Root<Brand> root = q.from(Brand.class); if (f != null) { f.addCriteria(cb, q, root); f.addOrder(cb, q, root, sortCol, ascending); } return em.createQuery(q).getResultList(); And here are the functions called: public void addCriteria(CriteriaBuilder cb, CriteriaQuery<?> q, Root<Brand> r) { } public void addOrder(CriteriaBuilder cb, CriteriaQuery<?> q, Root<Brand> r, String sortCol, boolean ascending) { if (ascending) { q.orderBy(cb.asc(r.get(sortCol))); } else { q.orderBy(cb.desc(r.get(sortCol))); } } If I try to set sortCol to something like "id.edition.number" I get the following error: javax.ejb.EJBException: java.lang.IllegalArgumentException: Unable to resolve attribute [id.name] against path Any idea how I could accomplish that? I tried searching online, but I couldn't find a hint about this... Also would be great if I could do a similar ORDER BY when I have a @ManyToOne relationship (for instance, "id.edition.number")

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  • GAE datastore querying integer fields

    - by ParanoidAndroid
    I notice strange behavior when querying the GAE datastore. Under certain circumstances Filter does not work for integer fields. The following java code reproduces the problem: log.info("start experiment"); DatastoreService datastore = DatastoreServiceFactory.getDatastoreService(); int val = 777; // create and store the first entity. Entity testEntity1 = new Entity(KeyFactory.createKey("Test", "entity1")); Object value = new Integer(val); testEntity1.setProperty("field", value); datastore.put(testEntity1); // create the second entity by using BeanUtils. Test test2 = new Test(); // just a regular bean with an int field test2.setField(val); Entity testEntity2 = new Entity(KeyFactory.createKey("Test", "entity2")); Map<String, Object> description = BeanUtilsBean.getInstance().describe(test2); for(Entry<String,Object> entry:description.entrySet()){ testEntity2.setProperty(entry.getKey(), entry.getValue()); } datastore.put(testEntity2); // now try to retrieve the entities from the database... Filter equalFilter = new FilterPredicate("field", FilterOperator.EQUAL, val); Query q = new Query("Test").setFilter(equalFilter); Iterator<Entity> iter = datastore.prepare(q).asIterator(); while (iter.hasNext()) { log.info("found entity: " + iter.next().getKey()); } log.info("experiment finished"); the log looks like this: INFO: start experiment INFO: found entity: Test("entity1") INFO: experiment finished For some reason it only finds the first entity even though both entities are actually stored in the datastore and both 'field' values are 777 (I see it in the Datastore Viewer)! Why does it matter how the entity is created? I would like to use BeanUtils, because it is convenient. The same problem occurs on the local devserver and when deployed to GAE.

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  • How to load a library that depends on another library, all from a jar file

    - by Philip
    I would like to ship my application as a self-contained jar file. The jar file should contain all the class files, as well as two shared libraries. One of these shared libraries is written for the JNI and is essentially an indirection to the other one (which is 100% C). I have first tried running my jar file without the libraries, but having them accessible through the LD_LIBRARY_PATH environment variable. That worked fine. I then put the JNI library into the jar file. I have read about loading libraries from jar files by copying them first to some temporary directory, and that worked well for me (note that the 100% C library was, I suppose, loaded as before). Now I want to put both libraries into the jar, but I don't understand how I can make sure that they will both be loaded. Sure I can copy them both to a temporary directory, but when I load the "indirection" one, it always gives me: java.lang.UnsatisfiedLinkError: /tmp/.../libindirect.so: /libpure.so: cannot open shared object file: No such file or directory I've tried to force the JVM to load the "100% C" library first by explicitely calling System.load(...) on its temporary file, but that didn't work better. I suspect the system is looking for it when resolving the links in libindirect.so but doesn't care about what the JVM loaded. Can anyone help me on that one? Thanks

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  • Why does Hibernate ignore the JPA2 standardized properties in my persistence.xml?

    - by Ophidian
    I have an extremely simple web application running in Tomcat using Spring 3.0.1, Hibernate 3.5.1, JPA 2, and Derby. I am defining all of my database connectivity in persistence.xml and merely using Spring for dependency injection. I am using embedded Derby as my database. Everything works correctly when I define the driver and url properties in persistence.xml in the classic Hibernate manner as thus: <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="hibernate.connection.url" value="jdbc:derby:webdb;create=true"/> The problems occur when I switch my configuration to the JPA2 standardized properties as thus: <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="javax.persistence.jdbc.url" value="jdbc:derby:webdb;create=true"/> When using the JPA2 property keys, the application bails hard with the following exception: java.lang.UnsupportedOperationException: The user must supply a JDBC connection Does anyone know why this is failing? NOTE: I have copied the javax... property strings straight from the Hibernate reference documentation, so a typo is extremely unlikely.

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  • Foosball result prediction

    - by Wolf
    In our office, we regularly enjoy some rounds of foosball / table football after work. I have put together a small java program that generates random 2vs2 lineups from the available players and stores the match results in a database afterwards. The current prediction of the outcome uses a simple average of all previous match results from the 4 involved players. This gives a very rough estimation, but I'd like to replace it with something more sophisticated, taking into account things like: players may be good playing as attacker but bad as defender (or vice versa) players do well against a specific opponent / bad against others some teams work well together, others don't skills change over time What would be the best algorithm to predict the game outcome as accurately as possible? Someone suggested using a neural network for this, which sounds quite interesting... but I do not have enough knowledge on the topic to say if that could work, and I also suspect it might take too many games to be reasonably trained. EDIT: Had to take a longer break from this due to some project deadlines. To make the question more specific: Given the following mysql table containing all matches played so far: table match_result match_id int pk match_start datetime duration int (match length in seconds) blue_defense int fk to table player blue_attack int fk to table player red_defense int fk to table player red_attack int fk to table player score_blue int score_red int How would you write a function predictResult(blueDef, blueAtk, redDef, redAtk) {...} to estimate the outcome as closely as possible, executing any sql, doing calculations or using external libraries?

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  • How do I use Google's Gson API to deserialize JSON properly?

    - by FK82
    Hi, In short, this is a sketch of the JSON object I want to parse in JAVA: { object1: { item1: //[String | Array | Object] , item2: // ... //<> more items object2: { // } //<> more objects } These are the POJO s I created for parsing (I'll leave out the import statements for brevity's sake): (1) The representation of the complete JSON object public class JObjectContainer { private List<JObject> jObjects ; public JObjectContainer() { // } //get & set methods } (2) The representation of the nested objects: public class JObject { private String id ; private List<JNode> jObjects ; public JObject() { // } //get & set methods } (3) The representation of the items: public class JNode { private JsonElement item1 ; private JsonElement item2 ; //<> more item fields public JNode() { // } //get & set methods } Now, creating a Gson instance (FileReader for importing the jsonFile), Gson gson = new Gson() ; JObjectContainer joc = gson(jsonFile,JObjectContainer.class) ; I get a NullPointerException whenever I try to access the parseable object (e.g. through a ListIterator). Gson does however create an object of the class I specified and does not throw any subsequent errors. I know that this has been done before. So, what am I missing? TIA

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  • how to Compute the average probe length for success and failure - Linear probe (Hash Tables)

    - by fang_dejavu
    hi everyone, I'm doing an assignment for my Data Structures class. we were asked to to study linear probing with load factors of .1, .2 , .3, ...., and .9. The formula for testing is: The average probe length using linear probing is roughly Success-- ( 1 + 1/(1-L)**2)/2 or Failure-- (1+1(1-L))/2. we are required to find the theoretical using the formula above which I did(just plug the load factor in the formula), then we have to calculate the empirical (which I not quite sure how to do). here is the rest of the requirements **For each load factor, 10,000 randomly generated positive ints between 1 and 50000 (inclusive) will be inserted into a table of the "right" size, where "right" is strictly based upon the load factor you are testing. Repeats are allowed. Be sure that your formula for randomly generated ints is correct. There is a class called Random in java.util. USE it! After a table of the right (based upon L) size is loaded with 10,000 ints, do 100 searches of newly generated random ints from the range of 1 to 50000. Compute the average probe length for each of the two formulas and indicate the denominators used in each calculationSo, for example, each test for a .5 load would have a table of size approximately 20,000 (adjusted to be prime) and similarly each test for a .9 load would have a table of approximate size 10,000/.9 (again adjusted to be prime). The program should run displaying the various load factors tested, the average probe for each search (the two denominators used to compute the averages will add to 100), and the theoretical answers using the formula above. .** how do I calculate the empirical success?

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  • How does CDI injection work in MDBs and @Scheduled beans?

    - by Nils-Petter Nilsen
    I'm working on a large Java EE 6 application that is deployed on JBoss 6 Final. My current tasks involve using @Inject consistently instead of @EJB, but I'm running into some problems on some types of beans, specifically @MessageDriven beans and beans with @Scheduled methods. What happens is that if I'm unlucky with the timing (for @Schedule) or if there are messages in the MDBs' queues at startup, instantiation of the beans will fail because the injected resources (which are EJBs themselves) are not bound yet. Because I use @Inject, I'm guessing that the EJB container considers my beans to be ready, since the container itself does not care about @Inject; it probably simply assumes that since there are no @EJB injections, the beans are ready for use. The injected CDI proxies will then fail because the resources to inject aren't actually bound yet. Tiny example: @Stateless @LocalBean public class MySupportingBean { public void doSomething() { ... } } @Singleton public class MyScheduledBean { @Inject private MySupportingBean supportingBean; @Schedule(second = "*/1", hour = "*", minute = "*", persistent = false) public void onTimeout() { supportingBean.doSomething(); } } The above example will probably not fail often because there are only two beans, but the project I'm working on binds lots of EJBs, which will amplify the problem. But it might fail because there is no guarantee that MySupportingBean is bound first, and if onTimeout is invoked before MySupportingBean is bound, then instantiation of MyScheduledBean will fail. If I used @EJB instead, MyScheduledBean wouldn't be bound until the dependency to MySupportingBean was satisfied. Note that the example will not fail in onTimeout itself, but when CDI attempts to inject MySupportingBean. I've read a lot of posts on different forums where many people argue that @Inject is always better. Generally, I agree, but how do they handle @Schedule or @MessageDriven combined with @Inject? In my experience, it comes down to dumb luck whether the beans will work or not in those cases, and the beans will fail arbitrarily, depending on which order the EJBs are deployed in, and when @Schedule or onMessage are invoked.

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  • proper use of volatile keyword

    - by luke
    I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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  • What does flushing thread local memory to global memory mean?

    - by Jack Griffith
    Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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  • Is it bad practice to make a setter return "this"?

    - by Ken Liu
    Is it a good or bad idea to make setters in java return "this"? public Employee setName(String name){ this.name = name; return this; } This pattern can be useful because then you can chain setters like this: list.add(new Employee().setName("Jack Sparrow").setId(1).setFoo("bacon!")); instead of this: Employee e = new Employee(); e.setName("Jack Sparrow"); ...and so on... list.add(e); ...but it sort of goes against standard convention. I suppose it might be worthwhile just because it can make that setter do something else useful. I've seen this pattern used some places (e.g. JMock, JPA), but it seems uncommon, and only generally used for very well defined APIs where this pattern is used everywhere. Update: What I've described is obviously valid, but what I am really looking for is some thoughts on whether this is generally acceptable, and if there are any pitfalls or related best practices. I know about the Builder pattern but it is a little more involved then what I am describing - as Josh Bloch describes it there is an associated static Builder class for object creation.

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