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• JPA merge fails due to duplicate key

  - by wobblycogs

  I have a simple entity, Code, that I need to persist to a MySQL database. public class Code implements Serializable { @Id private String key; private String description; ...getters and setters... } The user supplies a file full of key, description pairs which I read, convert to Code objects and then insert in a single transaction using em.merge(code). The file will generally have duplicate entries which I deal with by first adding them to a map keyed on the key field as I read them in. A problem arises though when keys differ only by case (for example: XYZ and XyZ). My map will, of course, contain both entries but during the merge process MySQL sees the two keys as being the same and the call to merge fails with a MySQLIntegrityConstraintViolationException. I could easily fix this by uppercasing the keys as I read them in but I'd like to understand exactly what is going wrong. The conclusion I have come to is that JPA considers XYZ and XyZ to be different keys but MySQL considers them to be the same. As such when JPA checks its list of known keys (or does whatever it does to determine whether it needs to perform an insert or update) it fails to find the previous insert and issuing another which then fails. Is this corrent? Is there anyway round this other than better filtering the client data? I haven't defined .equals or .hashCode on the Code class so perhaps this is the problem.

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• Synchronize DataGrid and DataForm in Silverlight 3

  - by SpiralGray

  I've been banging my head against the wall for a couple of days on this and it's time to ask for help. I've got a DataGrid and DataForm on the same UserControl. I'm using an MVVM approach so there is a single ViewModel for the UserControl. That ViewModel has a couple of properties that are relevant to this discussion: public ObservableCollection<VehicleViewModel> Vehicles { get; private set; } public VehicleViewModel SelectedVehicle { get { return selectedVehicle; } private set { selectedVehicle = value; OnPropertyChanged( "SelectedVehicle" ); } } In the XAML I've got the DataGrid and DataForm defined as follows: <data:DataGrid SelectionMode="Single" ItemsSource="{Binding Vehicles}" SelectedItem="{Binding SelectedVehicle, Mode=TwoWay}" AutoGenerateColumns="False" IsReadOnly="True"> <dataFormToolkit:DataForm CurrentItem="{Binding SelectedVehicle}" /> So as the SelectedItem changes on the DataGrid it should push that change back to the ViewModel and when the ViewModel raises the OnPropertyChanged the DataForm should refresh itself with the information for the newly-selected VehicleViewModel. However, the setter for SelectedVehicle is never being called and in the Output window of VS I'm seeing the following error: System.Windows.Data Error: ConvertBack cannot convert value 'xxxx.ViewModel.VehicleViewModel' (type 'xxxx.ViewModel.VehicleViewModel'). BindingExpression: Path='SelectedVehicle' DataItem='xxxx.ViewModel.MainViewModel' (HashCode=31664161); target element is 'System.Windows.Controls.DataGrid' (Name=''); target property is 'SelectedItem' (type 'System.Object').. System.MethodAccessException: xxxx.ViewModel.MainViewModel.set_SelectedVehicle(xxxx.ViewModel.VehicleViewModel) It sounds like it's having a problem converting from a VehicleViewModel to an object (or back again), but I'm confused as to why that would be (or even if I'm on the right track with that assumption). Each row/item in the DataGrid should be a VehicleViewModel (because the ItemsSource is bound to an ObservableCollection of that type), so when the SelectedItem changes it should be dealing with an instance of VehicleViewModel. Any insight would be appreciated.

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• What should i do to test EasyMock objects when using Generics ? EasyMock

  - by Arthur Ronald F D Garcia

  See code just bellow Our generic interface public interface Repository<INSTANCE_CLASS, INSTANCE_ID_CLASS> { void add(INSTANCE_CLASS instance); INSTANCE_CLASS getById(INSTANCE_ID_CLASS id); } And a single class public class Order { private Integer id; private Integer orderNumber; // getter's and setter's public void equals(Object o) { if(o == null) return false; if(!(o instanceof Order)) return false; // business key if(getOrderNumber() == null) return false; final Order other = (Order) o; if(!(getOrderNumber().equals(other.getOrderNumber()))) return false; return true; } // hashcode } And when i do the following test private Repository<Order, Integer> repository; @Before public void setUp { repository = EasyMock.createMock(Repository.class); Order order = new Order(); order.setOrderNumber(new Integer(1)); repository.add(order); EasyMock.expectLasCall().once(); EasyMock.replay(repository); } @Test public void addOrder() { Order order = new Order(); order.setOrderNumber(new Integer(1)); repository.add(order); EasyMock.verify(repository) } I get Unexpected method call add(br.com.smac.model.domain.Order@ac66b62): add(br.com.smac.model.domain.Order@ac66b62): expected: 1, actual: 0 Why does it not work as expected ??? What should i do to pass the test ???

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• Test-Driven Development Problem

  - by Zeck

  Hi guys, I'm newbie to Java EE 6 and i'm trying to develop very simple JAX-RS application. RESTfull web service working fine. However when I ran my test application, I got the following. What have I done wrong? Or am i forget any configuration? Of course i'm create a JNDI and i'm using Netbeans 6.8 IDE. In finally, thank you for any advise. My Entity: @Entity @Table(name = "BOOK") @NamedQueries({ @NamedQuery(name = "Book.findAll", query = "SELECT b FROM Book b"), @NamedQuery(name = "Book.findById", query = "SELECT b FROM Book b WHERE b.id = :id"), @NamedQuery(name = "Book.findByTitle", query = "SELECT b FROM Book b WHERE b.title = :title"), @NamedQuery(name = "Book.findByDescription", query = "SELECT b FROM Book b WHERE b.description = :description"), @NamedQuery(name = "Book.findByPrice", query = "SELECT b FROM Book b WHERE b.price = :price"), @NamedQuery(name = "Book.findByNumberofpage", query = "SELECT b FROM Book b WHERE b.numberofpage = :numberofpage")}) public class Book implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic(optional = false) @Column(name = "ID") private Integer id; @Basic(optional = false) @Column(name = "TITLE") private String title; @Basic(optional = false) @Column(name = "DESCRIPTION") private String description; @Basic(optional = false) @Column(name = "PRICE") private double price; @Basic(optional = false) @Column(name = "NUMBEROFPAGE") private int numberofpage; public Book() { } public Book(Integer id) { this.id = id; } public Book(Integer id, String title, String description, double price, int numberofpage) { this.id = id; this.title = title; this.description = description; this.price = price; this.numberofpage = numberofpage; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getNumberofpage() { return numberofpage; } public void setNumberofpage(int numberofpage) { this.numberofpage = numberofpage; } @Override public int hashCode() { int hash = 0; hash += (id != null ? id.hashCode() : 0); return hash; } @Override public boolean equals(Object object) { // TODO: Warning - this method won't work in the case the id fields are not set if (!(object instanceof Book)) { return false; } Book other = (Book) object; if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) { return false; } return true; } @Override public String toString() { return "com.entity.Book[id=" + id + "]"; } } My Junit test class: public class BookTest { private static EntityManager em; private static EntityManagerFactory emf; public BookTest() { } @BeforeClass public static void setUpClass() throws Exception { emf = Persistence.createEntityManagerFactory("E01R01PU"); em = emf.createEntityManager(); } @AfterClass public static void tearDownClass() throws Exception { em.close(); emf.close(); } @Test public void createBook() { Book book = new Book(); book.setId(1); book.setDescription("Mastering the Behavior Driven Development with Ruby on Rails"); book.setTitle("Mastering the BDD"); book.setPrice(25.9f); book.setNumberofpage(1029); em.persist(book); assertNotNull("ID should not be null", book.getId()); } } My persistence.xml jta-data-sourceBookstoreJNDI And exception is: May 7, 2009 11:10:37 AM org.hibernate.validator.util.Version INFO: Hibernate Validator bean-validator-3.0-JBoss-4.0.2 May 7, 2009 11:10:37 AM org.hibernate.validator.engine.resolver.DefaultTraversableResolver detectJPA INFO: Instantiated an instance of org.hibernate.validator.engine.resolver.JPATraversableResolver. [EL Info]: 2009-05-07 11:10:37.531--ServerSession(13671123)--EclipseLink, version: Eclipse Persistence Services - 2.0.0.v20091127-r5931 May 7, 2009 11:10:40 AM com.sun.enterprise.transaction.JavaEETransactionManagerSimplified initDelegates INFO: Using com.sun.enterprise.transaction.jts.JavaEETransactionManagerJTSDelegate as the delegate May 7, 2009 11:10:43 AM com.sun.enterprise.connectors.ActiveRAFactory createActiveResourceAdapter SEVERE: rardeployment.class_not_found May 7, 2009 11:10:43 AM com.sun.enterprise.connectors.ActiveRAFactory createActiveResourceAdapter SEVERE: com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR at com.sun.enterprise.connectors.ActiveRAFactory.createActiveResourceAdapter(ActiveRAFactory.java:104) at com.sun.enterprise.connectors.service.ResourceAdapterAdminServiceImpl.createActiveResourceAdapter(ResourceAdapterAdminServiceImpl.java:216) at com.sun.enterprise.connectors.ConnectorRuntime.createActiveResourceAdapter(ConnectorRuntime.java:352) at com.sun.enterprise.resource.naming.ConnectorObjectFactory.getObjectInstance(ConnectorObjectFactory.java:106) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304) at com.sun.enterprise.naming.impl.SerialContext.getObjectInstance(SerialContext.java:472) at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:437) at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:569) at javax.naming.InitialContext.lookup(InitialContext.java:396) at org.eclipse.persistence.sessions.JNDIConnector.connect(JNDIConnector.java:110) at org.eclipse.persistence.sessions.JNDIConnector.connect(JNDIConnector.java:94) at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:162) at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:584) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:228) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:368) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:151) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:207) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:195) at com.entity.BookTest.setUpClass(BookTest.java:31) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.ParentRunner.run(ParentRunner.java:220) at junit.framework.JUnit4TestAdapter.run(JUnit4TestAdapter.java:39) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:515) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:1031) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:888) Caused by: java.lang.ClassNotFoundException: com.sun.gjc.spi.ResourceAdapter at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at com.sun.enterprise.connectors.ActiveRAFactory.createActiveResourceAdapter(ActiveRAFactory.java:96) ... 32 more [EL Severe]: 2009-05-07 11:10:43.937--ServerSession(13671123)--Local Exception Stack: Exception [EclipseLink-7060] (Eclipse Persistence Services - 2.0.0.v20091127-r5931): org.eclipse.persistence.exceptions.ValidationException Exception Description: Cannot acquire data source [BookstoreJNDI]. Internal Exception: javax.naming.NamingException: Lookup failed for 'BookstoreJNDI' in SerialContext ,orb'sInitialHost=localhost,orb'sInitialPort=3700 [Root exception is javax.naming.NamingException: Failed to look up ConnectorDescriptor from JNDI [Root exception is com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR]] at org.eclipse.persistence.exceptions.ValidationException.cannotAcquireDataSource(ValidationException.java:451) at org.eclipse.persistence.sessions.JNDIConnector.connect(JNDIConnector.java:116) at org.eclipse.persistence.sessions.JNDIConnector.connect(JNDIConnector.java:94) at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:162) at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:584) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:228) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:368) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:151) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:207) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:195) at com.entity.BookTest.setUpClass(BookTest.java:31) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.ParentRunner.run(ParentRunner.java:220) at junit.framework.JUnit4TestAdapter.run(JUnit4TestAdapter.java:39) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:515) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:1031) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:888) Caused by: javax.naming.NamingException: Lookup failed for 'BookstoreJNDI' in SerialContext ,orb'sInitialHost=localhost,orb'sInitialPort=3700 [Root exception is javax.naming.NamingException: Failed to look up ConnectorDescriptor from JNDI [Root exception is com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR]] at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:442) at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:569) at javax.naming.InitialContext.lookup(InitialContext.java:396) at org.eclipse.persistence.sessions.JNDIConnector.connect(JNDIConnector.java:110) ... 23 more Caused by: javax.naming.NamingException: Failed to look up ConnectorDescriptor from JNDI [Root exception is com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR] at com.sun.enterprise.resource.naming.ConnectorObjectFactory.getObjectInstance(ConnectorObjectFactory.java:109) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304) at com.sun.enterprise.naming.impl.SerialContext.getObjectInstance(SerialContext.java:472) at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:437) ... 26 more Caused by: com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR at com.sun.enterprise.connectors.ActiveRAFactory.createActiveResourceAdapter(ActiveRAFactory.java:104) at com.sun.enterprise.connectors.service.ResourceAdapterAdminServiceImpl.createActiveResourceAdapter(ResourceAdapterAdminServiceImpl.java:216) at com.sun.enterprise.connectors.ConnectorRuntime.createActiveResourceAdapter(ConnectorRuntime.java:352) at com.sun.enterprise.resource.naming.ConnectorObjectFactory.getObjectInstance(ConnectorObjectFactory.java:106) ... 29 more Caused by: java.lang.ClassNotFoundException: com.sun.gjc.spi.ResourceAdapter at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at com.sun.enterprise.connectors.ActiveRAFactory.createActiveResourceAdapter(ActiveRAFactory.java:96) ... 32 more Exception Description: Cannot acquire data source [BookstoreJNDI]. Internal Exception: javax.naming.NamingException: Lookup failed for 'BookstoreJNDI' in SerialContext ,orb'sInitialHost=localhost,orb'sInitialPort=3700 [Root exception is javax.naming.NamingException: Failed to look up ConnectorDescriptor from JNDI [Root exception is com.sun.appserv.connectors.internal.api.ConnectorRuntimeException: Error in creating active RAR]])

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• Capturing Set Behavior with Mutating Elements

  - by Carl

  Using the Guava library, I have the following situation: SetMultimap<ImmutableFoo, Set<Foo>> setMM = HashMultimap.create(); Set<Foo> mask = Sets.newHashSet(); // ... some iteration construct { setMM.put(ImmutableFoo1, Sets.difference(SomeSetFoo1,mask)); setMM.put(ImmutableFoo1, Sets.difference(SomeSetFoo2,mask)); mask.add(someFoo); } that is, the same iteration to create the setMM is also used to create the mask - this can of course result in changes to hashCode()s and create duplicates within the SetMultimap backing. Ideally, I'd like the duplicates to drop without me having to make it happen, and avoid repeating the iteration to separately construct the multimap and mask. Any easy libraries/Set implementations to make that happen? Alternatively, can you identify a better way to drop the duplicates than: for (ImmutableFoo f : setMM.keySet()) setMM.putAll(f,setMM.removeAll(f)); revisiting the elements is probably not a performance problem, since I could combine a separate filter operation that needs to visit all the elements anyway.

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• C#/Java: Proper Implementation of CompareTo when Equals tests reference identity

  - by Paul A Jungwirth

  I believe this question applies equally well to C# as to Java, because both require that {c,C}ompareTo be consistent with {e,E}quals: Suppose I want my equals() method to be the same as a reference check, i.e.: public bool equals(Object o) { return this == o; } In that case, how do I implement compareTo(Object o) (or its generic equivalent)? Part of it is easy, but I'm not sure about the other part: public int compareTo(Object o) { if (! (o instanceof MyClass)) return false; MyClass other = (MyClass)o; if (this == other) { return 0; } else { int c = foo.CompareTo(other.foo) if (c == 0) { // what here? } else { return c; } } } I can't just blindly return 1 or -1, because the solution should adhere to the normal requirements of compareTo. I can check all the instance fields, but if they are all equal, I'd still like compareTo to return a value other than 0. It should be true that a.compareTo(b) == -(b.compareTo(a)), and the ordering should stay consistent as long as the objects' state doesn't change. I don't care about ordering across invocations of the virtual machine, however. This makes me think that I could use something like memory address, if I could get at it. Then again, maybe that won't work, because the Garbage Collector could decide to move my objects around. hashCode is another idea, but I'd like something that will be always unique, not just mostly unique. Any ideas?

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• WPF Border DesiredHeight

  - by Joseph Sturtevant

  The following Microsoft example code contains the following: <Grid> ... <Border Name="Content" ... > ... </Border> </Grid> <ControlTemplate.Triggers> <Trigger Property="IsExpanded" Value="True"> <Setter TargetName="ContentRow" Property="Height" Value="{Binding ElementName=Content,Path=DesiredHeight}" /> </Trigger> ... </ControlTemplate.Triggers> When run, however, this code generates the following databinding error: System.Windows.Data Error: 39 : BindingExpression path error: 'DesiredHeight' property not found on 'object' ''Border' (Name='Content')'. BindingExpression:Path=DesiredHeight; DataItem='Border' (Name='Content'); target element is 'RowDefinition' (HashCode=2034711); target property is 'Height' (type 'GridLength') Despite this error, the code works correctly. I have looked through the documentation and DesiredHeight does not appear to be a member of Border. Can anyone explain where DesiredHeight is coming from? Also, is there any way to resolve/suppress this error so my program output is clean?

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• Entity Framework 4 overwrite Equals and GetHashCode of an own class property

  - by Zhok

  Hi, I’m using Visual Studio 2010 with .NET 4 and Entity Framework 4. I’m working with POCO Classes and not the EF4 Generator. I need to overwrite the Equals() and GetHashCode() Method but that doesn’t really work. Thought it’s something everybody does but I don’t find anything about the problem Online. When I write my own Classes and Equals Method, I use Equals() of property’s, witch need to be loaded by EF to be filled. Like this: public class Item { public virtual int Id { get; set; } public virtual String Name { get; set; } public virtual List<UserItem> UserItems { get; set; } public virtual ItemType ItemType { get; set; } public override bool Equals(object obj) { Item item = obj as Item; if (obj == null) { return false; } return item.Name.Equals(this.Name) && item.ItemType.Equals(this.ItemType); } public override int GetHashCode() { return this.Name.GetHashCode() ^ this.ItemType.GetHashCode(); } } That Code doesn’t work, the problems are in Equals and GetHashCode where I try to get HashCode or Equal from “ItemType” . Every time I get a NullRefernceException if I try to get data by Linq2Entites. A dirty way to fix it, is to capture the NullReferenceException and return false (by Equals) and return base.GetHashCode() (by GethashCode) but I hope there is a better way to fix this problem. I’ve wrote a little test project, with SQL Script for the DB and POCO Domain, EDMX File and Console Test Main Method. You can download it here: Download

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• Is it possible to add JPA annotation to superclass instance variables?

  - by Kristofer Borgstrom

  Hi, I am creating entities that are the same for two different tables. In order do table mappings etc. different for the two entities but only have the rest of the code in one place - an abstract superclass. The best thing would be to be able to annotate generic stuff such as column names (since the will be identical) in the super class but that does not work because JPA annotations are not inherited by child classes. Here is an example: public abstract class MyAbstractEntity { @Column(name="PROPERTY") //This will not be inherited and is therefore useless here protected String property; public String getProperty() { return this.property; } //setters, hashCode, equals etc. methods } Which I would like to inherit and only specify the child-specific stuff, like annotations: @Entity @Table(name="MY_ENTITY_TABLE") public class MyEntity extends MyAbstractEntity { //This will not work since this field does not override the super class field, thus the setters and getters break. @Column(name="PROPERTY") protected String property; } Any ideas or will I have to create fields, getters and setters in the child classes? Thanks, Kris

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• Culture Sensitive GetHashCode

  - by user114928

  Hi, I'm writing a c# application that will process some text and provide basic query functions. In order to ensure the best possible support for other languages, I am allowing the users of the application to specify the System.Globalization.CultureInfo (via the "en-GB" style code) and also the full range of collation options using the System.Globalization.CompareOptions flags enum. For regular string comparison I'm then using a combination of: a) String.Compare overload that accepts the culture and options b) For some bulk processes I'm caching the byte data (KeyData) from CompareInfo.GetSortKey (overload that accepts the options) and using a byte-by-byte comparison of the KeyData. This seemed fine (although please comment if you think these two methods shouldn't be mixed), but then I had reason to use the HashSet< class which only has an overload for IEqualityComparer<. MS documentation seems to suggest that I should use StringComparer (which implements both IEqualityComparer< and IComparer<), but this only seems to support the "IgnoreCase" option from CompareOptions and not "IgnoreKanaType", "IgnoreSymbols", "IgnoreWidth" etc. I'm assuming that a StringComparer that ignores these other options could produce different hashcodes for two strings that might be considered the same using my other comparison options. I'd therefore get incorrect results from my application. Only thought at the moment is to create my own IEqualityComparer< that generates a hashcode from the SortKey.KeyData and compares eqality be using the String.Compare overload. Any suggestions?

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• Java: Initializing a public static field in superclass that needs a different value in every subclas

  - by BinaryMuse

  Good evening, I am developing a set of Java classes so that a container class Box contains a List of a contained class Widget. A Widget needs to be able to specify relationships with other Widgets. I figured a good way to do this would be to do something like this: public abstract class Widget { public static class WidgetID { // implementation stolen from Google's GWT private static int nextHashCode; private final int index; public WidgetID() { index = ++nextHashCode; } public final int hashCode() { return index; } } public abstract WidgetID getWidgetID(); } so sublcasses of Widget could: public class BlueWidget extends Widget { public static final WidgetID WIDGETID = new WidgetID(); @Override public WidgetID getWidgetID() { return WIDGETID; } } Now, BlueWidget can do getBox().addWidgetRelationship(RelationshipTypes.SomeType, RedWidget.WIDGETID, and Box can iterate through it's list comparing the second parameter to iter.next().getWidgetID(). Now, all this works great so far. What I'm trying to do is keep from having to declare the public static final WidgetID WIDGETID in all the subclasses and implement it instead in the parent Widget class. The problem is, if I move that line of code into Widget, then every instance of a subclass of Widget appears to get the same static final WidgetID for their Subclassname.WIDGETID. However, making it non-static means I can no longer even call Subclassname.WIDGETID. So: how do I create a static WidgetID in the parent Widget class while ensuring it is different for every instance of Widget and subclasses of Widget? Or am I using the wrong tool for the job here? Thanks!

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• Why do case class companion objects extend FunctionN?

  - by retronym

  When you create a case class, the compiler creates a corresponding companion object with a few of the case class goodies: an apply factory method matching the primary constructor, equals, hashCode, and copy. Somewhat oddly, this generated object extends FunctionN. scala> case class A(a: Int) defined class A scala> A: (Int => A) res0: (Int) => A = <function1> This is only the case if: There is no manually defined companion object There is exactly one parameter list There are no type arguments The case class isn't abstract. Seems like this was added about two years ago. The latest incarnation is here. Does anyone use this, or know why it was added? It increases the size of the generated bytecode a little with static forwarder methods, and shows up in the #toString() method of the companion objects: scala> case class A() defined class A scala> A.toString res12: java.lang.String = <function0>

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• Delphi : Handling the fact that Strings are not Objects

  - by awmross

  I am trying to write a function that takes any TList and returns a String representation of all the elements of the TList. I tried a function like so function ListToString(list:TList<TObject>):String; This works fine, except you can't pass a TList to it. E2010 Incompatible types: 'TList<System.TObject>' and 'TList<System.string>' In Delphi, a String is not an Object. To solve this, I've written a second function: function StringListToString(list:TList<string>):String; Is this the only solution? Are there other ways to treat a String as more 'object-like'? In a similar vein, I also wanted to write an 'equals' function to compare two TLists. Again I run into the same problem function AreListsEqual(list1:TList<TObject>; list2:TList<TObject>):boolean; Is there any way to write this function (perhaps using generics?) so it can also handle a TList? Are there any other tricks or 'best practises' I should know about when trying to create code that handles both Strings and Objects? Or do I just create two versions of every function? Can generics help? I am from a Java background but now work in Delphi. It seems they are lately adding a lot of things to Delphi from the Java world (or perhaps the C# world, which copied them from Java). Like adding equals() and hashcode() to TObject, and creating a generic Collections framework etc. I'm wondering if these additions are very practical if you can't use Strings with them.

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• How to store child objects on GAE using JDO from Scala

  - by Gero

  Hi, I'm have a parent-child relation between 2 classes, but the child objects are never stored. I do get an warning: "org.datanucleus.store.appengine.MetaDataValidator checkForIllegalChildField: Unable to validate relation net.vermaas.kivanotify.model.UserCriteria.internalCriteria" but it is unclear to me why this occurs. Already tried several alternatives without luck. The parent class is "UserCriteria" which has a List of "Criteria" as children. The classes are defined as follows (Scala): class UserCriteria(tu: String, crit: Map[String, String]) extends LogHelper { @PrimaryKey @Persistent{val valueStrategy = IdGeneratorStrategy.IDENTITY} var id = KeyFactory.createKey("UserCriteria", System.nanoTime) @Persistent var twitterUser = tu @Persistent var internalCriteria: java.util.List[Criteria] = flatten(crit) def flatten(crits: Map[String, String]) : java.util.List[Criteria] = { val list = new java.util.ArrayList[Criteria] for (key <- crits.keySet) { list.add(new Criteria(this, key, crits(key))) } list } def criteria: Map[String, String] = { val crits = mutable.Map.empty[String, String] for (i <- 0 to internalCriteria.size-1) { crits(internalCriteria.get(i).name) = internalCriteria.get(i).value } Map.empty ++ crits } // Stripped the equals, canEquals, hashCode, toString code to keep the code snippet short... } @PersistenceCapable @EmbeddedOnly class Criteria(uc: UserCriteria, nm: String, vl: String) { @Persistent var userCriteria = uc @Persistent var name = nm @Persistent var value = vl override def toString = { "Criteria name: " + name + " value: " + value } } Any ideas why the childs are not stored? Or why I get the error message? Thanks, Gero

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• Hashtable is that fast

  - by Costa

  Hi s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]. Is the hash function of the java string, I assume the rest of languages is similar or close to this implementation. If we have hash-Table and a list of 50 elements. each element is 7 chars ABCDEF1, ABCDEF2, ABCDEF3..... ABCDEFn If each bucket of hashtable contains 5 strings (I think this function will make it one string per bucket, but let us assume it is 5). If we call col.Contains("ABCDEFn"); // will do 6 comparisons and discover the difference on the 7th. The hash-table will take around 70 operations (multiplication and additions) to get the hashcode and to compare with 5 strings in bucket. and BANG it found. For list it will take around 300 comparisons to find it. for the case that there is only 10 elements, the list will take around 70 operations but the Hashtable will take around 50 operations. and note that hashtable operations are more time consuming (it is multiplications). I conclude that HybirdDictionary in .Net probably is the best choice for that most cases that require Hashtable with unknown size, because it will let me use a list till the list becomes more than 10 elements. still need something like HashSet rather than a Dictionary of keys and values, I wonder why there is no HybirdSet!! So what do u think? Thanks

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• JPA 2.0 Provider Hibernate

  - by Rooh

  I have very strange problem we are using jpa 2.0 with hibernate annotations based Database generated through JPA DDL is true and MySQL as Database; i will provide some reference classes and then my porblem. @MappedSuperclass public abstract class Common implements serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; @ManyToOne @JoinColumn private Address address; //with all getter and setters //as well equal and hashCode } @Entity public class Parent extends Common{ private String name; @OneToMany(cascade = {CascadeType.MERGE,CascadeType.PERSIST}, mappedBy = "parent") private List<Child> child; //setters and rest of class } @Entity public class Child extends Common{ //some properties with getter/setters } @Entity public class Address implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; private String street; //rest of class with get/setter } as in code you can see that parents and child classes extends Common class so both have address property and id , the problem occurs when change the address refference in parent class it reflect same change in all child objects in list and if change address refference in child class then on merge it will change address refference of parent as well i am not able to figure out is it is problem of jpa or hibernate

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• How should I return different types in a method based on the value of a string in Java?

  - by Siracuse

  I'm new to Java and I have come to having the following problem: I have created several classes which all implement the interface "Parser". I have a JavaParser, PythonParser, CParser and finally a TextParser. I'm trying to write a method so it will take either a File or a String (representing a filename) and return the appropriate parser given the extension of the file. Here is some psuedo-code of what I'm basically attempting to do: public Parser getParser(String filename) { String extension = filename.substring(filename.lastIndexOf(".")); switch(extension) { case "py": return new PythonParser(); case "java": return new JavaParser(); case "c": return new CParser(); default: return new TextParser(); } } In general, is this the right way to handle this situation? Also, how should I handle the fact that Java doesn't allow switching on strings? Should I use the .hashcode() value of the strings? I feel like there is some design pattern or something for handling this but it eludes me. Is this how you would do it?

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• java: retrieving the "canonical value" from a Set<T> where T has a custom equals()

  - by Jason S

  I have a class Foo which overrides equals() and hashCode() properly. I would like to also would like to use a HashSet<Foo> to keep track of "canonical values" e.g. I have a class that I would like to write like this, so that if I have two separate objects that are equivalent I can coalesce them into references to the same object: class Canonicalizer<T> { final private Set<T> values = new HashSet<T>(); public T findCanonicalValue(T value) { T canonical = this.values.get(value); if (canonical == null) { // not in the set, so put it there for the future this.values.add(value); return value; } else { return canonical; } } } except that Set doesn't have a "get" method that would return the actual value stored in the set, just the "contains" method that returns true or false. (I guess that it assumes that if you have an object that is equal to a separate object in the set, you don't need to retrieve the one in the set) Is there a convenient way to do this? The only other thing I can think of is to use a map and a list: class Canonicalizer<T> { // warning: neglects concurrency issues final private Map<T, Integer> valueIndex = new HashMap<T, Integer>(); final private List<T> values = new ArrayList<T>(); public T findCanonicalValue(T value) { Integer i = this.valueIndex.get(value); if (i == null) { // not in the set, so put it there for the future i = this.values.size(); this.values.add(value); this.valueIndex.put(value, i); return value; } else { // in the set return this.values.get(i); } } }

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• Avoiding duplicate objects in Java deserialization

  - by YGL

  I have two lists (list1 and list2) containing references to some objects, where some of the list entries may point to the same object. Then, for various reasons, I am serializing these lists to two separate files. Finally, when I deserialize the lists, I would like to ensure that I am not re-creating more objects than needed. In other words, it should still be possible for some entry of List1 to point to the same object as some entry in List2. MyObject obj = new MyObject(); List<MyObject> list1 = new ArrayList<MyObject>(); List<MyObject> list2 = new ArrayList<MyObject>(); list1.add(obj); list2.add(obj); // serialize to file1.ser ObjectOutputStream oos = new ObjectOutputStream(...); oos.writeObject(list1); oos.close(); // serialize to file2.ser oos = new ObjectOutputStream(...); oos.writeObject(list2); oos.close(); I think that sections 3.4 and A.2 of the spec say that deserialization strictly results in the creation of new objects, but I'm not sure. If so, some possible solutions might involve: Implementing equals() and hashCode() and checking references manually. Creating a "container class" to hold everything and then serializing the container class. Is there an easy way to ensure that objects are not duplicated upon deserialization? Thanks.

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• Error when running a basic Hadoop code

  - by Abhishek Shivkumar

  I am running a hadoop code that has a partitioner class inside the job. But, when I run the command hadoop jar Sort.jar SecondarySort inputdir outputdir I am getting a runtime error that says class KeyPartitioner not org.apache.hadoop.mapred.Partitioner. I have ensured that the KeyPartitioner class has extended the Partitioner class, but why am I getting this error? Here is the driver code: JobConf conf = new JobConf(getConf(), SecondarySort.class); conf.setJobName(SecondarySort.class.getName()); conf.setJarByClass(SecondarySort.class); conf.setInputFormat(TextInputFormat.class); conf.setOutputFormat(TextOutputFormat.class); conf.setMapOutputKeyClass(StockKey.class); conf.setMapOutputValueClass(Text.class); conf.setPartitionerClass((Class<? extends Partitioner<StockKey, DoubleWritable>>) KeyPartitioner.class); conf.setMapperClass((Class<? extends Mapper<LongWritable, Text, StockKey, DoubleWritable>>) StockMapper.class); conf.setReducerClass((Class<? extends Reducer<StockKey, DoubleWritable, Text, Text>>) StockReducer.class); and here is the code of the partitioner class: public class KeyPartitioner extends Partitioner<StockKey, Text> { @Override public int getPartition(StockKey arg0, Text arg1, int arg2) { int partition = arg0.name.hashCode() % arg2; return partition; } }

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• JPA 2.0 Provider Hibernate Spring MVC 3.0

  - by user558019

  Dear All i have very strange problem we are using jpa 2.0 with hibernate and spring 3.0 mvc annotations based Database generated through JPA DDL is true and MySQL as Database; i will provide some refference classes and then my porblem. public abstract class Common implements serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; @ManyToOne @JoinColumn private Address address; //with all getter and setters //as well equal and hashCode } public class Parent extends Common{ private String name; @OneToMany(cascade = {CascadeType.MERGE,CascadeType.PERSIST}, mappedBy = "parent") private List<Child> child; //setters and rest of class } public class child extends Common{ //some properties with getter/setters } public class Address implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; private String street; //rest of class with get/setter } as in code you can see that parents and child classes extends Common class so both have address property and id , the problem occurs when change the address refference in parent class it reflect same change in all child objects in list and if change address refference in child class then on merge it will change address refference of parent as well i am not able to figure out is it is problem of jpa or hibernate or spring thanks in advance

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• Downloading Large JSON File to local file using Java

  - by user1279675

  I'm attempting to download a JSON from the following URL - http://api.crunchbase.com/v/1/companies.js - to a local file. I'm using Java 1.7 and the following JSON Libraries - http://www.json.org/java/ - to attempt to make it work. Here's my code: public static void download(String address, String localFileName) { OutputStream out = null; URLConnection conn = null; InputStream in = null; try { URL url = new URL(address); out = new BufferedOutputStream( new FileOutputStream(localFileName)); conn = url.openConnection(); in = conn.getInputStream(); byte[] buffer = new byte[1024]; int numRead; long numWritten = 0; while ((numRead = in.read(buffer)) != -1) { out.write(buffer, 0, numRead); numWritten += numRead; System.out.println(buffer.length); System.out.println(" " + buffer.hashCode()); } System.out.println(localFileName + "\t" + numWritten); } catch (Exception exception) { exception.printStackTrace(); } finally { try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException ioe) { } } } When I run the code everything seems to work until midway through the loop the program seems to stop and not continue reading the JSON Object. Does anyone know why this would stop reading? How could I fix the issue?

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• WPF Debugging AvalonEdit binding to Document property.

  - by kubal5003

  Hello, all day long I am sitting and trying to find out why binding to AvalonEdits Document property isn't working. AvalonEdit is an advanced WPF text editor - part of the SharpDevelop project.(it's going to be used in SharpDevelop v4 Mirador). So when I set up a simple project - one TextEditor (that's the AvalonEdits real name in the library) and made a simple class that has one property - Document and it returns a dummy object with some static text the binding is working perfectly. However in real life solution I'm binding a collection of SomeEditor objects to TabControl. TabControl has DataTemplate for SomeEditor and there's the TextEditor object. <TabControl Grid.Column="1" x:Name="tabControlFiles" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" > <TabControl.Resources> <DataTemplate DataType="{x:Type m:SomeEditor}"> <a:TextEditor Document="{Binding Path=Document, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource NoopConverter}, IsAsync=True}" x:Name="avalonEdit"></a:TextEditor> </DataTemplate> </TabControl.Resources> <TabControl.ItemContainerStyle> <Style BasedOn="{StaticResource TabItemStyle}" TargetType="{x:Type TabItem}"> <Setter Property="IsSelected" Value="{Binding IsSelected}"></Setter> </Style> </TabControl.ItemContainerStyle> </TabControl> This doesn't work. What I've investigated so far: DataContext of TextEditor is set to the proper instance of SomeEditor TextEditors Document property is set to some other instance than SomeEditor.Document property when I set breakpoint to no-op converter that is attached to that binding it shows me the correct value for Document (the converter is used!) I also dug through the VisualTree to obtain reference to TextEditor and called GetBindingExpression(TextEditor.DocumentProperty) and this did return nothing WPF produces the following information: System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Document; DataItem='SomeEditor' (HashCode=26280264); target element is 'TextEditor' (Name='avalonEdit'); target property is 'Document' (type 'TextDocument') SomeEditor instance that is bound to already has a created and cached copy of Document before the binding occurs. The getter is never called. Anyone can tell me what might be wrong? Why BindingExpression isn't set ? Why property getter is never called?

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• Trouble binding command in grid menu item.

  - by Pete

  I have a grid that's inside a usercontrol derived class called MediatedUserControl. I'm adding a context menu to let the user delete an item, but I've been unable to figure out how to bind the command to my command property. I'm using MVVM and my viewmodel implements a public ICommand property called DeleteSelectedItemCommand. However, when the view is displayed, I get the following message in the output window: System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='BRO.View.MediatedUserControl', AncestorLevel='1''. BindingExpression:Path=DataContext.DeleteSelectedItemCommand; DataItem=null; target element is 'BarButtonItem' (HashCode=6860584); target property is 'Command' (type 'ICommand') I feel like I generally have a good handle on bindings like this and can't figure out what it is I'm missing here. Thanks for any help you can provide. <dxg:GridControl HorizontalAlignment="Left" Margin="12,88,0,0" x:Name="gridControl1" VerticalAlignment="Top" Height="500" Width="517" DataSource="{Binding ItemList}" BorderBrush="{StaticResource {x:Static SystemColors.ActiveBorderBrushKey}}" ShowBorder="True" Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}" UseLayoutRounding="False" DataContext="{Binding}"> <dxg:GridControl.Columns> <dxg:GridColumn FieldName="Code" Header="Code" Width="107" /> <dxg:GridColumn FieldName="Name" Header="Item" Width="173" /> <dxg:GridColumn FieldName="PricePerItem" Header="Unit Price" Width="70"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> <dxg:GridColumn FieldName="Quantity" Header="Qty" Width="50" AllowEditing="True" /> <dxg:GridColumn FieldName="TotalPrice" Header="Total Price" Width="90"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> </dxg:GridControl.Columns> <dxg:GridControl.View> <dxg:TableView ShowIndicator="False" ShowGroupPanel="False" MultiSelectMode="Row" AllowColumnFiltering="False" AllowBestFit="False" AllowFilterEditor="False" AllowEditing="False" AllowGrouping="False" AllowSorting="False" AllowResizing="False" AllowMoving="False" AllowMoveColumnToDropArea="False" AllowDateTimeGroupIntervalMenu="False" > <dxg:TableView.RowCellMenuCustomizations> <dxb:BarButtonItem Name="deleteRowItem" Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=view:MediatedUserControl, AncestorLevel=1}, Path=DataContext.DeleteSelectedItemCommand}"> </dxb:BarButtonItem> </dxg:TableView.RowCellMenuCustomizations> </dxg:TableView> </dxg:GridControl.View>

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• How to access static members in a Velocity template?

  - by matt b

  I'm not sure if there is a way to do this in Velocity or not: I have a User POJO which a property named Status, which looks like an enum (but it is not, since I am stuck on Java 1.4), the definition looks something like this: public class User { // default status to User private Status status = Status.USER; public void setStatus(Status status) { this.status = status; } public Status getStatus() { return status; } And Status is a static inner class: public static final class Status { private String statusString; private Status(String statusString) { this.statusString = statusString; } public final static Status USER = new Status("user"); public final static Status ADMIN = new Status("admin"); public final static Status STATUS_X = new Status("blah"); //.equals() and .hashCode() implemented as well } With this pattern, a user status can easily be tested in a conditional such as if(User.Status.ADMIN.equals(user.getStatus())) ... ... without having to reference any constants for the status ID, any magic numbers, etc. However, I can't figure out how to test these conditionals in my Velocity template with VTL. I'd like to just print a simple string based upon the user's status, such as: Welcome <b>${user.name}</b>! <br/> <br/> #if($user.status == com.company.blah.User.Status.USER) You are a regular user #elseif($user.status == com.company.blah.User.Status.ADMIN) You are an administrator #etc... #end But this throws an Exception that looks like org.apache.velocity.exception.ParseErrorException: Encountered "User" at webpages/include/dashboard.inc[line 10, column 21] Was expecting one of: "[" ... From the VTL User Guide, there is no mention of accessing a Java class/static member directly in VTL, it appears that the right hand side (RHS) of a conditional can only be a number literal, string literal, property reference, or method reference. So is there any way that I can access static Java properties/references in a Velocity template? I'm aware that as a workaround, I could embed the status ID or some other identifier as a reference in my controller (this is a web MVC application using Velocity as the View technology), but I strongly do not want to embed any magic numbers or constants in the view layer.

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