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  • Architecture Best Practice (MVC): Repository Returns Object & Object Member Accessed Directly or Repository Returns Object Member

    - by coderabbi
    Architecturally speaking, which is the preferable approach (and why)? $validation_date = $users_repository->getUser($user_id)->validation_date; Seems to violate Law of Demeter by accessing member of object returned by method call Seems to violate Encapsulation by accessing object member directly $validation_date = $users_repository->getUserValidationDate($user_id); Seems to violate Single Responsibility Principle as $users_repository no longer just returns User objects

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  • Difference between LiveCD, LiveUSB, full-install, and persistence?

    - by Jay
    I am currently running Ubuntu as a guest vm on a Win 7 host via VirtualBox, but I would like to have a portable version of Ubuntu when I am not using my laptop. I am unsure as to the difference between the following: 1)LiveCD with persistence; 2)LiveCD without persistence; 3)LiveUSB with persistence; 4)LiveUSB without persistence; 5)Full-install. I have a USB flash drive (32GB), and I also have empty DVDs lying around. I know that persistence means that data can be saved, but I am unsure as to which option to choose. What is the difference between a LiveUSB and a full-install on a USB thumbdrive and why would I want to pick one over the other? Thanks for any help.

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  • When would you want two references to the same object?

    - by HCBPshenanigans
    In Java specifically, but likely in other languages as well; When would it be useful to have two references to the same object? Example: Dog a = new Dog(); Dob b = a; Is there a situation where this would be useful? Why would this be a preferred solution to using a whenever you want to interact with the object represented by a? Edit: Can I just say that all of your dog related examples are Delightful!

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  • java.lang.NoClassDefFoundError: javax/persistence/Persistence

    - by ManWard
    hi , i'm using Netbeans 6.8 and build simple Maven web application project. create Entity and main file for persist Entity [also create persist unit] and use EclipsLink. but when i run main file get this error : Exception in thread "main" java.lang.NoClassDefFoundError: javax/persistence/Persistence at Main.main(Main.java:34) Caused by: java.lang.ClassNotFoundException: javax.persistence.Persistence at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:248) ... 1 more in netbeans projects window and in my project libraries folder only add this package : javaee-web-api-6.0.jar [provided] please help me for solve this Error thanks

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  • Netbeans / persistence API error

    - by Danny
    I am following this tutorial, I'm using netbeans 6.5.1 http://www.netbeans.org/kb/docs/java/gui-db-custom.html When I get to the part where I create the "new entity class from database", which is in the "Customizing the Master/Detail View" section of the tutoiral. I can't ever compile because I get this error in the task list (and I get a runtime error when I run)... Atleast I think these two are related. Error Named queries can be defined only on an Entity or MappedSuperclass class. Countries.java 27 C:/Users/Danny/dev/NetBeansProjects/Test/src/test Error Named queries can be defined only on an Entity or MappedSuperclass class. Products.java 28 C:/Users/Danny/dev/NetBeansProjects/Test/src/test note that all I do is do newentity classes from database, and do exactly as the tutorial says. I stopped on the tutoral at the "Adding Dialog Boxes" heading, because the tutorial writer says the application should be "partially functional" which makes me think it should atleast RUN. I haven't edited the generated code outside of what I've been instructed to do. This is the output produced by the netbeans output console: run: Jun 23, 2009 3:03:23 PM org.jdesktop.application.Application$1 run SEVERE: Application class test.TestApp failed to launch javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyBusinessRecordsPU: Provider named oracle.toplink.essentials.PersistenceProvider threw unexpected exception at create EntityManagerFactory: oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException Local Exception Stack: Exception [TOPLINK-30005] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: sun.misc.Launcher$AppClassLoader@11b86e7 Internal Exception: javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:143) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:169) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:110) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at test.TestView.initComponents(TestView.java:337) at test.TestView.(TestView.java:39) at test.TestApp.startup(TestApp.java:19) at org.jdesktop.application.Application$1.run(Application.java:171) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Caused by: javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:643) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.callPredeploy(JavaSECMPInitializer.java:171) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initPersistenceUnits(JavaSECMPInitializer.java:239) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initialize(JavaSECMPInitializer.java:255) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:155) ... 14 more Caused by: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.EntityManagerSetupException.predeployFailed(EntityManagerSetupException.java:228) ... 19 more Caused by: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.ValidationException.invalidMapping(ValidationException.java:1069) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataValidator.throwInvalidMappingEncountered(MetadataValidator.java:275) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.accessors.OneToManyAccessor.process(OneToManyAccessor.java:161) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.accessors.RelationshipAccessor.processRelationship(RelationshipAccessor.java:290) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProject.processRelationshipDescriptors(MetadataProject.java:579) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProject.process(MetadataProject.java:512) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProcessor.processAnnotations(MetadataProcessor.java:246) at oracle.toplink.essentials.ejb.cmp3.persistence.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:370) at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:607) ... 18 more The following providers: oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider Returned null to createEntityManagerFactory. at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:154) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at test.TestView.initComponents(TestView.java:337) at test.TestView.(TestView.java:39) at test.TestApp.startup(TestApp.java:19) at org.jdesktop.application.Application$1.run(Application.java:171) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Exception in thread "AWT-EventQueue-0" java.lang.Error: Application class test.TestApp failed to launch at org.jdesktop.application.Application$1.run(Application.java:177) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyBusinessRecordsPU: Provider named oracle.toplink.essentials.PersistenceProvider threw unexpected exception at create EntityManagerFactory: oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException Local Exception Stack: Exception [TOPLINK-30005] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: sun.misc.Launcher$AppClassLoader@11b86e7 Internal Exception: javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:143) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:169) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:110) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at test.TestView.initComponents(TestView.java:337) at test.TestView.(TestView.java:39) at test.TestApp.startup(TestApp.java:19) at org.jdesktop.application.Application$1.run(Application.java:171) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Caused by: javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:643) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.callPredeploy(JavaSECMPInitializer.java:171) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initPersistenceUnits(JavaSECMPInitializer.java:239) at oracle.toplink.essentials.internal.ejb.cmp3.JavaSECMPInitializer.initialize(JavaSECMPInitializer.java:255) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:155) ... 14 more Caused by: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [MyBusinessRecordsPU] failed. Internal Exception: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.EntityManagerSetupException.predeployFailed(EntityManagerSetupException.java:228) ... 19 more Caused by: Exception [TOPLINK-7244] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: An incompatible mapping has been encountered between [class test.Products] and [class test.Orders]. This usually occurs when the cardinality of a mapping does not correspond with the cardinality of its backpointer. at oracle.toplink.essentials.exceptions.ValidationException.invalidMapping(ValidationException.java:1069) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataValidator.throwInvalidMappingEncountered(MetadataValidator.java:275) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.accessors.OneToManyAccessor.process(OneToManyAccessor.java:161) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.accessors.RelationshipAccessor.processRelationship(RelationshipAccessor.java:290) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProject.processRelationshipDescriptors(MetadataProject.java:579) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProject.process(MetadataProject.java:512) at oracle.toplink.essentials.internal.ejb.cmp3.metadata.MetadataProcessor.processAnnotations(MetadataProcessor.java:246) at oracle.toplink.essentials.ejb.cmp3.persistence.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:370) at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:607) ... 18 more The following providers: oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider Returned null to createEntityManagerFactory. at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:154) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at test.TestView.initComponents(TestView.java:337) at test.TestView.(TestView.java:39) at test.TestApp.startup(TestApp.java:19) at org.jdesktop.application.Application$1.run(Application.java:171) ... 8 more BUILD SUCCESSFUL (total time: 2 seconds) I'm thinking my netbeans application must be misconfigured or something, I can't seem to find anyone with the same problem as myself

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  • No Persistence provider for EntityManager named ...

    - by Robert A Henru
    I have my persistence.xml with the same name, using toplink, under META-INF directory. Then I have my code calling it with... EntityManagerFactory emfdb = Persistence.createEntityManagerFactory("agisdb"); Yet, I got the following error message 2009-07-21 09:22:41,018 [main] ERROR - No Persistence provider for EntityManager named agisdb javax.persistence.PersistenceException: No Persistence provider for EntityManager named agisdb at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:89) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:60) Here is the persistence.xml... <?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0"> <persistence-unit name="agisdb"> <class>com.agis.livedb.domain.AddressEntity</class> <class>com.agis.livedb.domain.TrafficCameraEntity</class> <class>com.agis.livedb.domain.TrafficPhotoEntity</class> <class>com.agis.livedb.domain.TrafficReportEntity</class> <properties> <property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/agisdb"/> <property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/> <property name="toplink.jdbc.user" value="root"/> <property name="toplink.jdbc.password" value="password"/> </properties> </persistence-unit> </persistence> It should have been in the classpath... Yet, I got the above error... Really appreciate any help... Thanks

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  • How to safely copy an object?

    - by Prog
    This question is going to be a little long. Please bear with me. Something that happened in a project of mine made me think about how to safely copy objects. I'll present the situation I had and then ask a question. There was a class SomeClass: class SomeClass{ Thing[] things; public SomeClass(Thing[] things){ this.things = things; } // irrelevant stuff omitted public SomeClass copy(){ return new SomeClass(things); } } There was another class Processor that takes SomeClass objects, copies them (via someClassInstance.copy()), manipulates the copy's state, and returns the copy. Here it is: class Processor{ public SomeClass processObject(SomeClass object){ SomeClass copy = object.copy(); manipulateTheCopy(copy); return copy; } // irrelevant stuff omitted } I ran this, and it had bugs. I looked into these bugs, and it turned out that the manipulations Processor does on copy actually affect not only the copy, but also the original SomeClass object that was passed into processObject. I found out that it was because the original and the copy shared state - because the original passed it's field things into the copy when creating it. This made me realize that copying objects is harder than simply instantiating them with the same fields as the original. For the two objects to be completely disconnected, without any shared state, each of the fields passed to the copy also has to be copied. And if that object contains other objects - they have to be copied too. And so on. So basically, in order to be able to actually copy an object, each class in the system must have a copy() method, that also invokes copy() on all of it's fields, and so on. So for example, for copy() in SomeClass to work, it needs to look like this: public SomeClass copy(){ Thing[] copyThings = new Thing[things.length]; for(int i=0; i<things.length; i++) copyThings[i] = things[i].copy(); return new SomeClass(copyThings); } And if Thing has object fields of it's own, than it's own copy() method must be appropriate: class Thing{ Apple apple; Pencil pencil; int number; public Thing(Apple apple, Pencil pencil, int number){ this.apple = apple; this.pencil = pencil; this.number = number; } public Thing copy(){ // 'number' is a primitve. return new Thing(apple.getCopy(), pencil.getCopy(), number); } } And so on. Of course, instead of all classes having a copy() method, the copying mechanism can happen in all of the getters and the constructors of classes (unless places where it isn't suitable, for example when the field points to an external object, not to an object that 'is part' of this object). Still, that means that in order to be able to safely copy an object - most classes would have to have copying mechanisms in their getters. My question is divided into two parts: How frequently do you need to get a copy of an object? Is this a regular issue? Is the technique described common and/or reasonable? Or is there a better way to make safe copies of objects? Or is there an easier way to safely copy objects, without them sharing any state?

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  • Should an object know its own ID?

    - by xenoterracide
    obj.id seems fairly common and also seems to fall within the range of something an object could know about itself. I find myself asking why should my object know its own id? It doesn't seem to have a reason to have it? One of the main reason for it existing is retrieve it, and so my repositories need to know it, and thus use it for database interaction. I also once encountered a problem where I wanted to serialize an object to JSON for a RESTful API where the id did not seem to fit in the payload, but only the URI and including it in the object made that more difficult. Should an object know it's own id? why or why not?

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  • Best Persistence choice for J2EE-App with frequently changing Data Model

    - by Ben-G
    Whenever I develop a J2EE-Application, I at some point decide to switch from my dummy Persistence (Simply Using Lists and other Data Structures) to some Sort of Database Persistence. Mostly when I hope the Data Model is more or less complete. From this point on, changes to the data model become exhausting, but unluckily they occur rather often. I've used different Object-Relational-Mappers (iBatis, Hibernate) for my projects. They definitely reduce the pain coming with Data Model changes, but they anyway let me adjust code/configuration at 3 or 4 places for every single change. To me, that's cumbersome and error prone. I made a better experience with DB4O, which simply persists Java Objects as they are, but I believe it's performance does not scale for huge applications. Is there anyway to maintain performance while letting out all the ugly configuration work? I'm seeking a performant framework which really hides persistence from my code. Wish for thinking? Or am I missing out THE technology? Hope you can help.

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  • Object oriented design importance

    - by user5507
    I started studying Object Oriented Design and Modelling using the this book by James Rumbaugh. It uses a tool called Object Modeling Technique (OMT). I have certain newbie questions. I searched the net, but couldn't get answers The book is pretty old. Don't know why the school told me to learn this. I know OMT is a predecessor of the Unified Modeling Language (UML). So its a waste? Whether the concepts change very much when we move from OMT to UML? I know OMT has Object, Dynamic and Functional Model. Wikipedia says UML is compatible with OMT and UML is a model too. As per wikipedia the UML models are Static and Dynamic and they are represented by different diagrams like class, object, activity, sequence..... I couldn't find the equivalence of this in OMT. I read that there are many object oriented development methods like OMT, Booch,.... Which one is used by Industry ? Where could I get a comparison of different Object oriented development methods?

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  • Taking Object Oriented development to the next level

    - by Songo
    Can you mention some advanced OO topics or concepts that one should be aware of? I have been a developer for 2 years now and currently aiming for a certain company that requires a web developer with a minimum experience of 3 years. I imagine the interview will have the basic object oriented topics like (Abstraction, Polymorphism, Inheritance, Design patterns, UML, Databases and ORMs, SOLID principles, DRY principle, ...etc) I have these topics covered, but what I'm looking forward to is bringing up topics such as Efferent Coupling, Afferent Coupling, Instability, The law of Demeter, ...etc. Till few days ago I never knew such concepts existed (maybe because I'm a communication engineer basically not a CS graduate.) Can you please recommend some more advanced topics concerning object oriented programming?

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  • How to use the client object model with SharePoint2010

    - by ybbest
    In SharePoint2010, you can use client object model to communicate with SharePoint server. Today, I’d like to show you how to achieve this by using the c# console application. You can download the solution here. 1. Create a Console application in visual studio and add the following references to the project. 2. Insert your code as below ClientContext context = new ClientContext("http://demo2010a"); Web currentWeb = context.Web; context.Load(currentWeb, web =&gt; web.Title); context.ExecuteQuery(); Console.WriteLine(currentWeb.Title); Console.ReadLine(); 3. Run your code then you will get the web title displayed as shown below Note: If you got the following errors, you need to change your target framework from .Net Framework 4 client profile to .Net Framework 4 as shown below: Change from TO

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  • Object behaviour or separate class?

    - by Andrew Stephens
    When it comes to OO database access you see two common approaches - the first is to provide a class (say "Customer") with methods such as Retrieve(), Update(), Delete(), etc. The other is to keep the Customer class fairly lightweight (essentially just properties) and perform the database access elsewhere, e.g. using a repository. This choice of approaches doesn't just apply to database access, it can crop up in many different OOD scenarios. So I was wondering if one way is preferable over the other (although I suspect the answer will be "it depends")! Another dev on our team argues that to be truly OO the class should be "self-contained", i.e. providing all the methods necessary to manipulate and interact with that object. I personally prefer the repository approach - I don't like bloating the Customer class with all that functionality, and I feel it results in cleaner code having it elsewhere, but I can't help thinking I'm seriously violating core OO concepts! And what about memory implications? If I retrieve thousands of Customer objects I'm assuming those with the data access methods will take up a lot more memory than the property-only objects?

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  • Any enlightenment for understanding Object Oriented Programming? [closed]

    - by ????
    I studied computer science near the end of 1980s, and wasn't taught OOP that formally. With Pascal or C, when I understand the top-down design of functions, and the idea of black box, then everything just seem to make sense, as if there is a "oh I get it!" -- some kind of totally getting it and enlightenment feeling. But with OOP, all I know was the mechanics: the class, instance, method, inheritance, polymorphism, encapsulation. It was like, I knew all the "this is how it is", but never had the feeling of "I totally get it", the enlightened feeling. Would somebody be able to describe it, or point to a chapter in some book or paper which talks about OOP so that the reader can feel: "I totally get it!" on OOP?

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  • Invalid XML in persistence.xml : Init method

    - by James.Elsey
    I'm getting the following error when I try to startup my application on google app engine: Failed startup of context com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@8fcc7b{/,/base/data/home/apps/sales-tracker/3.340980411948080671} org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'clientDao' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Cannot resolve reference to bean 'entityManagerFactory' while setting bean property 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Invalid XML in persistence unit from URL [file:/base/data/home/apps/sales-tracker/3.340980411948080671/WEB-INF/classes/META-INF/persistence.xml] at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:275) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1245) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:548) at org.mortbay.jetty.servlet.Context.startContext(Context.java:136) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:191) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168) at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123) at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:243) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5485) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5483) at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24) at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:398) at com.google.net.rpc.impl.Server$2.run(Server.java:852) at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56) at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:536) at com.google.net.rpc.impl.Server.startRpc(Server.java:807) at com.google.net.rpc.impl.Server.processRequest(Server.java:369) at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:442) at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319) at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290) at com.google.net.async.Connection.handleReadEvent(Connection.java:474) at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:831) at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:207) at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:103) at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251) at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:404) at java.lang.Thread.run(Unknown Source) Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Invalid XML in persistence unit from URL [file:/base/data/home/apps/sales-tracker/3.340980411948080671/WEB-INF/classes/META-INF/persistence.xml] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1338) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269) ... 47 more Caused by: java.lang.IllegalArgumentException: Invalid XML in persistence unit from URL [file:/base/data/home/apps/sales-tracker/3.340980411948080671/WEB-INF/classes/META-INF/persistence.xml] at org.springframework.orm.jpa.persistenceunit.PersistenceUnitReader.readPersistenceUnitInfos(PersistenceUnitReader.java:151) at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.readPersistenceUnitInfos(DefaultPersistenceUnitManager.java:303) at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.preparePersistenceUnitInfos(DefaultPersistenceUnitManager.java:275) at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.afterPropertiesSet(DefaultPersistenceUnitManager.java:260) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:192) at org.springframework.orm.jpa.AbstractEnti My persistence.xml looks as follows, as taken from the GAE documentation <?xml version="1.0" encoding="UTF-8" ?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"version="1.0"> <persistence-unit name="transactions-optional"> <provider>org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider</provider> <properties> <property name="datanucleus.NontransactionalRead" value="true" /> <property name="datanucleus.NontransactionalWrite" value="true" /> <property name="datanucleus.ConnectionURL" value="appengine" /> </properties> </persistence-unit> </persistence> Is there something wrong with my persistence file? Or could my errors be caused elsewhere? Can someone please give me some pointers thanks

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  • Generic object to object mapping with parametrized constructor

    - by Rody van Sambeek
    I have a data access layer which returns an IDataRecord. I have a WCF service that serves DataContracts (dto's). These DataContracts are initiated by a parametrized constructor containing the IDataRecord as follows: [DataContract] public class DataContractItem { [DataMember] public int ID; [DataMember] public string Title; public DataContractItem(IDataRecord record) { this.ID = Convert.ToInt32(record["ID"]); this.Title = record["title"].ToString(); } } Unfortanately I can't change the DAL, so I'm obliged to work with the IDataRecord as input. But in generat this works very well. The mappings are pretty simple most of the time, sometimes they are a bit more complex, but no rocket science. However, now I'd like to be able to use generics to instantiate the different DataContracts to simplify the WCF service methods. I want to be able to do something like: public T DoSomething<T>(IDataRecord record) { ... return new T(record); } So I'd tried to following solutions: Use a generic typed interface with a constructor. doesn't work: ofcourse we can't define a constructor in an interface Use a static method to instantiate the DataContract and create a typed interface containing this static method. doesn't work: ofcourse we can't define a static method in an interface Use a generic typed interface containing the new() constraint doesn't work: new() constraint cannot contain a parameter (the IDataRecord) Using a factory object to perform the mapping based on the DataContract Type. does work, but: not very clean, because I now have a switch statement with all mappings in one file. I can't find a real clean solution for this. Can somebody shed a light on this for me? The project is too small for any complex mapping techniques and too large for a "switch-based" factory implementation.

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  • Can a loosely typed language be considered true object oriented?

    - by user61852
    Can a loosely typed programming language like PHP be really considered object oriented? I mean, the methods don't have returning types and method parameters has no declared type either. Doesn't class design require methods to have a return type? Don't methods signatures have specifically-typed parameters? How can OOP techniques help you code in PHP if you always have to check the types of parameters received because the language doesn't enforce types? Please, if I'm wrong, explain it to me. When you design things using UML, then code classes in PHP with no return-typed methods and no-type parameters... Is the code really compliant with the UML design? You spend time designing the architecture of your software, then the compiler doesn't force the programmer to follow your design while coding, letting he/she assign any object variable to any other variable with no "type-mismatch" warning.

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  • JPA persistence.xml share same jar file

    - by user213855
    Hi! I'm wondering if I can share the same jar file for several persistence units.. I mean: I have two persistence units described in my persistence.xml file and the entities are not in the same JAR. Entities are in a separated JAR file but, in that one, there are entites for both persistence units. I think I red somewhere that I coould use tag something like this: externalEntities.jar#com.mycompany.EntityA so I could separate them. I tried this solution and it doesn't work. Now I guess that it couldn't be done to package all entities (for two different persistence units) in the same JAR file. What do yo think?

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  • I don't get object-oriented programming

    - by Joel J. Adamson
    Note: this question is an edited excerpt from a blog posting I wrote a few months ago. After placing a link to the blog in a comment on Programmers.SE someone requested that I post a question here so that they could answer it. This posting is my most popular, as people seem to type "I don't get object-oriented programming" into Google a lot. Feel free to answer here, or in a comment at Wordpress. What is object-oriented programming? No one has given me a satisfactory answer. I feel like you will not get a good definition from someone who goes around saying “object” and “object-oriented” with his nose in the air. Nor will you get a good definition from someone who has done nothing but object-oriented programming. No one who understands both procedural and object-oriented programming has ever given me a consistent idea of what an object-oriented program actually does. Can someone please give me their ideas of the advantages of object-oriented programming?

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  • I don't get object-oriented programming

    - by Joel J. Adamson
    Note: this question is an edited excerpt from a blog posting I wrote a few months ago. After placing a link to the blog in a comment on Programmers.SE someone requested that I post a question here so that they could answer it. This posting is my most popular, as people seem to type "I don't get object-oriented programming" into Google a lot. Feel free to answer here, or in a comment at Wordpress. What is object-oriented programming? No one has given me a satisfactory answer. I feel like you will not get a good definition from someone who goes around saying “object” and “object-oriented” with his nose in the air. Nor will you get a good definition from someone who has done nothing but object-oriented programming. No one who understands both procedural and object-oriented programming has ever given me a consistent idea of what an object-oriented program actually does. Can someone please give me their ideas of the advantages of object-oriented programming?

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  • EJB3 - using 2 persistence units within a transaction (Exception: Local transaction already has 1 no

    - by Sorcha
    I am trying to use 2 persistence units within the same transaction in a JEE application deployed on Glassfish. The 2 persistence units are defined in persistence.xml, as follows: <persistence-unit name="BeachWater"> <jta-data-source>jdbc/BeachWater</jta-data-source> ... <persistence-unit name="LIMS"> <jta-data-source>jdbc/BeachWaterLIMS</jta-data-source> ... These persistence units correspond to JDBC resources and connection pools which I had defined in Glassfish as follows (include one here as both are identical apart from names & database connection info): JDBC Resource: JNDI Name: jdbc/BeachWaterLIMS Pool Name: BEACHWATER_LIMS Connection Pool: Name: BEACHWATER_LIMS Datasource Classname: com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource Resource Type: javax.sql.ConnectionPoolDataSource There are 3 stateless session beans, LimsServiceBean, AnalysisServiceBean and AnalysisDataTransformationServiceBean. Here are the relevant snippets from LimsServiceBean: @PersistenceContext(unitName = "LIMS") EntityManager em; ... public ArrayList<Sample> getLatestLIMSData() { Query q = em.createNamedQuery("Sample.findBySubTypeStatus"); return new ArrayList<Sample>(q.getResultList()); } From AnalysisServiceBean: @PersistenceContext(unitName = "BeachWater") EntityManager em; ... public ArrayList<AnalysisType> getAllAnalysisTypes() { Query q = em.createNamedQuery("AnalysisType.findAll"); return new ArrayList<AnalysisType>(q.getResultList()); } And from AnalysisDataTransformationServiceBean: @EJB private AnalysisService analysisService; @EJB private LimsService limsService; public void transformData() { List<AnalysisType> analysisTypes = analysisService.getAllAnalysisTypes(); ArrayList<Sample> samples = limsService.getLatestLIMSData(); This call to limsService.getLatestLIMSData() caused the following exception: [exec] Caused by: javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean; nested exception is: Exception [TOPLINK-4002] (Oracle TopLink Essentials - 2.1 (Build b60e-fcs (12/23/2008))): oracle.toplink.essentials.exceptions.DatabaseException [exec] Internal Exception: java.sql.SQLException: Error in allocating a connection. Cause: java.lang.IllegalStateException: Local transaction already has 1 non-XA Resource: cannot add more resources. Having consulted this page, http://msdn.microsoft.com/en-us/library/ms378484.aspx (among many others), I tried changing the definition of the connection pools to: Connection Pool: Name: BEACHWATER_LIMS Datasource Classname: com.microsoft.sqlserver.jdbc.SQLServerXADataSource Resource Type: javax.sql.XADataSource Ping via the Glassfish admin console succeeds, but call to analysisService.getAllAnalysisTypes() now throws an exception: Caused by: javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean; nested exception is: Exception [TOPLINK-4002] (Oracle TopLink Essentials - 2.1 (Build b60e-fcs (12/23/2008))): oracle.toplink.essentials.exceptions.DatabaseException Internal Exception: java.sql.SQLException: Error in allocating a connection. Cause: javax.transaction.SystemException Any ideas?

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  • "[object Object]" passed instead of the actual object as parameter

    - by Andrew Latham
    I am using Heroku with a Ruby on Rails application, and running from Safari. I have the following Ajax call: $.ajax({ type : 'POST', url : '/test_page', data : {stuff: arr1}, dataType : 'script' }); arr1 is supposed to be an array of objects. There's a console.log right before that, and it is: [Object, Object, Object, Object, Object, ...] However, I got an error on the server side when I made this ajax call. The logs showed 2012-10-01T03:13:34+00:00 app[web.1]: Parameters: {"stuff"=>"[object Object]"} 2012-10-01T03:13:34+00:00 app[web.1]: WARNING: Can't verify CSRF token authenticity 2012-10-01T03:13:34+00:00 app[web.1]: NoMethodError (undefined method `to_hash' for "[object Object]":String): 2012-10-01T03:13:34+00:00 app[web.1]: Completed 500 Internal Server Error in 1ms I'm unable to replicate the error. It's really confusing to me - what would cause that string to sometimes be passed to the server instead of the object?

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  • WPF: Reloading app parts to handle persistence as well as memory management.

    - by Ingó Vals
    I created a app using Microsoft's WPF. It mostly handles data reading and input as well as associating relations between data within specific parameters. As a total beginner I made some bad design decision ( not so much decisions as using the first thing I got to work ) but now understanding WPF better I'm getting the urge to refactor my code with better design principles. I had several problems but I guess each deserves it's own question for clarity. Here I'm asking for proper ways to handle the data itself. In the original I wrapped each row in a object when fetched from database ( using LINQ to SQL ) somewhat like Active Record just not active or persistence (each app instance had it's own data handling part). The app has subunits handling different aspects. However as it was setup it loaded everything when started. This creates several problems, for example often it wouldn't be neccesary to load a part unless we were specifically going to work with that part so I wan't some form of lazy loading. Also there was problem with inner persistance because you might create a new object/row in one aspect and perhaps set relation between it and different object but the new object wouldn't appear until the program was restarted. Persistance between instances of the app won't be huge problem because of the small amount of people using the program. While I could solve this now using dirty tricks I would rather refactor the program and do it elegantly, Now the question is how. I know there are several ways and a few come to mind: 1) Each aspect of the program is it's own UserControl that get's reloaded/instanced everytime you navigate to it. This ensures you only load up the data you need and you get some persistancy. DB server located on same LAN and tables are small so that shouldn't be a big problem. Minor drawback is that you would have to remember the state of each aspect so you wouldn't always start at beginners square. 2) Having a ViewModel type object at the base level of the app with lazy loading and some kind of timeout. I would then propegate this object down the visual tree to ensure every aspect is getting it's data from the same instance 3) Semi active record data layer with static load methods. 4) Some other idea What in your opinion is the most practical way in WPF, what does MVVM assume?

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  • Best Practices for serializing/persisting String Object Dictionary entities

    - by Mark Heath
    I'm noticing a trend towards using a dictionary of string to object (or sometimes string to string), instead of strongly typed objects. For example, the new Katana project makes heavy use of IDictionary<string,object>. This approach avoids the need to continually update your entity classes/DTOs and the database tables that persist them with new properties. It also avoids the need to create new derived entity types to support new types of entity, since the Dictionary is flexible enough to store any arbitrary properties. Here's a contrived example: class StorageDevice { public int Id { get; set; } public string Name { get; set; } } class NetworkShare : StorageDevice { public string Path { get; set; } public string LoginName { get; set; } public string Password { get; set; } } class CloudStorage : StorageDevice { public string ServerUri { get; set } public string ContainerName { get; set; } public int PortNumber { get; set; } public Guid ApiKey { get; set; } } versus: class StorageDevice { public IDictionary<string, object> Properties { get; set; } } Basically I'm on the lookout for any talks, books or articles on this approach, so I can pick up on any best practices / difficulties to avoid. Here's my main questions: Does this approach have a name? (only thing I've heard used so far is "self-describing objects") What are the best practices for persisting these dictionaries into a relational database? Especially the challenges of deserializing them successfully with strongly typed languages like C#. Does it change anything if some of the objects in the dictionary are themselves lists of strongly typed entities? Should a second dictionary be used if you want to temporarily store objects that are not to be persisted/serialized across a network, or should you use some kind of namespacing on the keys to indicate this?

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