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  • Many-to-Many Relationship (with properties) in Google App Engine for Java

    - by rvandervort
    I understand from the official documentation on unowned relationships that the app must use sets of Key objects on either side of the relationship. This makes perfect sense. Coming from many years of RDBM-style programming, though, I'm pretty confused about how I can model properties of that relationship itself. For example, if I have entities Category and Entry in my many-to-many relationship and would like to persist a dateAdded property, or some other data that are only relevant when both sides of the relationship are known. I suppose it would be possible to create a third class : CategoryEntry that links the two, but this seems like a kludge. What is the proposed way to model this kind of situation ?

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  • Database Developers Can Now Save 20%

    - by stephen.garth
    Database developers can now increase productivity and save money at the same time. For a limited time, Oracle Store is offering a 20% discount on Oracle SQL Developer Data Modeler. Just enter the code SQLDDM at checkout to get the discount. Oracle SQL Developer Data Modeler is an independent, standalone product with a full spectrum of data and database modeling tools and utilities, including modeling for Entity Relationship Diagrams (ERD), Relational (database design), Data Type and Multi-dimensional modeling, full forward and reverse engineering and DDL code generation. SQL Developer Data Modeler can connect to any supported Oracle Database and is platform independent. Save 20% on Oracle SQL Developer Data Modeler at Oracle Store - Discount Code SQLDDM Find out more about Oracle SQL Developer and Oracle SQL Developer Data Modeler var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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  • Extending both T and SomeInterface<T> in Java

    - by Graeme Moss
    I want to create a class that takes two parameters. One should be typed simply as T. The other should be typed as something that extends both T and SomeInterface. When I attempt this with public class SomeClass<T, S extends SomeInterface<T> & T> then Java complains with "The type T is not an interface; it cannot be specified as a bounded parameter" and if instead I attempt to create an interface for S with public interface TandSomeInterface<T> extends SomeInterface<T>, T then Java complains with "Cannot refer to the type parameter T as a supertype" Is there any way to do this in Java? I think you can do it in C++...?

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  • OpenXml - How to identify whether the paragraph extends to next page

    - by K.V.
    From aspx page, I dynamically add paragraphs to a word document using OpenXml SDK. In this case, a page break within a paragraph is not allowed. So in case a paragraph starts in middle of page 1 and extends to page2 then it should actually start in Page2. However, if it ends in the same page it is okay. How to achieve this? Is there a way to set in th document that page break is not allowed within a paragraph? Any input is highly appreciated.

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  • Why doesn't Java Map extends Collection?

    - by polygenelubricants
    I was surprised by the fact that Map<?,?> is not a Collection<?>. I thought it'd make a LOT of sense if it was declared as such: public interface Map<K,V> extends Collection<Map.Entry<K,V>> After all, a Map<K,V> is a collection of Map.Entry<K,V>, isn't it? So is there a good reason why it's not implemented as such?

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  • Java reflection field value in extends class

    - by Lukasz Wozniczka
    Hello i hava got problem with init value with java reflection. i have got simple class public class A extends B { private String name; } public class B { private String superName; } and also i have got simple function: public void createRandom(Class<T> clazz , List<String> classFields){ try { T object = clazz.newInstance(); for(String s : classFields){ clazz.getDeclaredField(s); } } catch(Exception e){ } } My function do other stuff but i have got problem because i have got error : java.lang.NoSuchFieldException: superName How can i set all class field also field from super Class using reflection ??

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  • OSX / Kernel extensions: problem locating a driver (that extends IOSCSIPeripheralDeviceType00)

    - by LG
    Hi, I'm implementing a driver that extends IOSCSIPeripheralDeviceType00 as I need to send custom SCSI commands to a device. I'm following the VendorSpecificType00 and SimpleUserClient examples and http://wagerlabs.com/writing-a-mac-osx-usb-device-driver-that-impl as an example. I built my kernel extension and it loads fine with kextload and it shows up in kextstat. The problem is that I can't locate it in my user space code. Here's the important (I think) part of: my driver code: #define super IOSCSIPeripheralDeviceType00 OSDefineMetaClassAndStructors(com_mycompany_driver_Foo, IOSCSIPeripheralDeviceType00) my user client code: #define super IOUserClient OSDefineMetaClassAndStructors(com_mycompany_driver_FooUserClient, IOUserClient) the plist: CFBundleIdentifier -> com.mycompany.driver.Foo IOCLass -> com_mycompany_driver_Foo IOUserClientClass -> com_mycompany_driver_FooUserClient IOProviderClass -> IOSCSIPeripheralDeviceNub Here's how I try to locate the driver in my user space code (similar to SimpleUserClient): dictRef = IOServiceMatching("com_mycompany_driver_Foo"); kernResult = IOServiceGetMatchingServices(kIOMasterPortDefault, dictRef, &iterator); When I execute the code, iterator is 0. I noticed that in the VendorSpecificType00 code, the localization of the driver is done differently: dictRef = IOServiceMatching("IOBlockStorageServices"); kr = IOServiceGetMatchingServices(kIOMasterPortDefault, dictRef, &iter); while ((service = IOIteratorNext(iter))) { io_registry_entry_t parent; kr = IORegistryEntryGetParentEntry(service, kIOServicePlane, &parent); ... // We're only interested in the parent object if it's our driver class. if (IOObjectConformsTo(parent, "com_apple_dts_driver_VendorSpecificType00")) { I tried doing that but it didn't work either. Thanks for reading and your help, -L

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  • Textbox extends outside of the grid cell in .Net 4.0 (but not in 3.5)

    - by Bryant
    There seems to be a change in behaviour between .Net 3.5 and .Net 4.0. If I define a window as: <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="500" > <Grid> <Grid.ColumnDefinitions> <ColumnDefinition MinWidth="300" /> <ColumnDefinition /> </Grid.ColumnDefinitions> <TextBox Grid.Column="1" ScrollViewer.CanContentScroll="True" ScrollViewer.HorizontalScrollBarVisibility="Auto" Text="abc abc abc abc abc abc abc abc abcabc abc abcabc abc abc abc abc abc" /> </Grid> </Window> In .Net 3.5 the textbox correctly contains itself within the grid cell but in .Net 4.0 it extends beyond the cell and so gets clipped. This only happens if the MinWidth of the first column is greater than 50% of the overall width. Does anyone know how to get 4.0 to exhibit the same behavior as 3.5?

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  • Behavior of Struts2 and convention-plugin when there is Index(extends ActionSupport)

    - by hanishi
    We have an Action class named 'Index' immediately under com.example.common.action and is annotated @ParentPackage('default') which is declared in package directive in struts.xml and has "/" for its namespace and extends "struts-default". It also declares @Result so that it responses with jsp files corresponding the string values returned by its execute() method. In our struts.xml, the following struts setting is configured along with other necessary configurations that are needed for convention-plugin. <constant name="struts.action.extension" value=","/> When accessing /my_context/none_existing_path, the request apparently hits this Index class and the contents of the jsp declared in the Index's @Result section gets returned. However, if we provide /my_context/, we receive the following error: HTTP Status 404-There is no Action mapped for namespace[/] and action name [] associated with context path [/my_context]. We want to know the reason why accessing /my_context/none_existing_path, where none_existing_path has no matching action, can fallback to Index class, but error is returned when when the URL requested is just /my_context/. Currently, our convention-plugin settings are declared as follows: <constant name="struts.convention.package.locators.basePackage" value="com.example"/> <constant name="struts.convention.package.locators" value="action"/> Strangely, if we changed the value of the struts.convention.package.locators.basePackage to om.example.common, in which the aforementioned Index file can be immediately found by narrowing the search scope, requesting /my_context/ displays the content of the jsps declared in @Result section of the Index class. However, as our action classes are distributed throughout the com.example.[a-z].action packages, where [a-z] represents the large volume of directories we have in our package structure, we cannot use this trick as a workaround. We have also tried placing index.jsp at the top level of the class path, and have the index.jsp redirect to /my_context/index, which worked but not what we want. Could this be a bug? We appreciate your responses. Thank you in advance. EDIT: JIRA registered, problem solved (from Struts 2.3.12 up)

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  • Java Generics : What is PECS?

    - by peakit
    Hi, I came across PECS (short for Producer extends and Consumer super) while reading on Generics. Can someone explain me how to use PECS to resolve confusion between extends and super? Thanks in advance !

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  • [Java] Cannot find symbol

    - by m00st
    I've created a class called Entity this is the superclass. Actor has successfully extended Entity; now trying to do the same with Item results in the Cannot find symbol error. Here is example code: public class Actor extends Entity { Actor(String filename, int x, int y) { super(filename, x, y); } } works just fine but this doesn't: public class Item extends Entity { }

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  • PHP Classes Extend

    - by John
    I have two classes that work seperate from another, but they extend the same class. Is it possible to have them work the same instance of the extended class. I'm wanting the constructor of the extended class to run only once. I know this isn't right but something like this: <?php $oApp = new app; class a extends $oApp {} class b extends $oApp {}

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  • Entity Framework won't SaveChanges on new entity with two-level relationship

    - by Tim Rourke
    I'm building an ASP.NET MVC site using the ADO.NET Entity Framework. I have an entity model that includes these entities, associated by foreign keys: Report(ID, Date, Heading, Report_Type_ID, etc.) SubReport(ID, ReportText, etc.) - one-to-one relationship with Report. ReportSource(ID, Name, Description) - one-to-many relationship with Sub_Report. ReportSourceType(ID, Name, Description) - one-to-many relationship with ReportSource. Contact (ID, Name, Address, etc.) - one-to-one relationship with Report_Source. There is a Create.aspx page for each type of SubReport. The post event method returns a new Sub_Report entity. Before, in my post method, I followed this process: Set the properties for a new Report entity from the page's fields. Set the SubReport entity's specific properties from the page's fields. Set the SubReport entity's Report to the new Report entity created in 1. Given an ID provided by the page, look up the ReportSource and set the Sub_Report entity's ReportSource to the found entity. SaveChanges. This workflow succeeded just fine for a couple of weeks. Then last week something changed and it doesn't work any more. Now instead of the save operation, I get this Exception: UpdateException: "Entities in 'DIR2_5Entities.ReportSourceSet' participate in the 'FK_ReportSources_ReportSourceTypes' relationship. 0 related 'ReportSourceTypes' were found. 1 'Report_Source_Types' is expected." The debug visualizer shows the following: The SubReport's ReportSource is set and loaded, and all of its properties are correct. The Report_Source has a valid ReportSourceType entity attached. In SQL Profiler the prepared SQL statement looks OK. Can anybody point me to what obvious thing I'm missing? TIA Notes: The Report and SubReport are always new entities in this case. The Report entity contains properties common to many types of reports and is used for generic queries. SubReports are specific reports with extra parameters varying by type. There is actually a different entity set for each type of SubReport, but this question applies to all of them, so I use SubReport as a simplified example.

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  • Batch faulting in a to-many relationship for a collection of objects

    - by indragie
    Scenario: Let's say I have an entity called Author that has a to-many relationship called books to the Book entity (inverse relationship author). If I have an existing collection of Author objects, I want to fault in the books relationship for all of them in a single fetch request. Code This is what I've tried so far: NSArray *authors = ... // array of `Author` objects NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Book"]; fetchRequest.returnsObjectsAsFaults = NO; fetchRequest.predicate = [NSPredicate predicateWithFormat:@"author IN %@", authors]; Executing this fetch request does not result in the books relationship of the objects in the authors array being faulted in (inspected via logging). I've also tried doing the fetch request the other way around: NSArray *authors = ... // array of `Author` objects NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Author"]; fetchRequest.returnsObjectsAsFaults = NO; fetchRequest.predicate = [NSPredicate predicateWithFormat:@"SELF IN %@", authors]; fetchRequest.relationshipKeypathsForPrefetching = @[@"books"]; This doesn't fire the faults either. What's the appropriate way of going about doing this?

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  • Save many-to-one relationship from JSON into Core Data

    - by Snow Crash
    I'm wanting to save a Many-to-one relationship parsed from JSON into Core Data. The code that parses the JSON and does the insert into Core Data looks like this: for (NSDictionary *thisRecipe in recipes) { Recipe *recipe = [NSEntityDescription insertNewObjectForEntityForName:@"Recipe" inManagedObjectContext:insertionContext]; recipe.title = [thisRecipe objectForKey:@"Title"]; NSDictionary *ingredientsForRecipe = [thisRecipe objectForKey:@"Ingredients"]; NSArray *ingredientsArray = [ingredientsForRecipe objectForKey:@"Results"]; for (NSDictionary *thisIngredient in ingredientsArray) { Ingredient *ingredient = [NSEntityDescription insertNewObjectForEntityForName:@"Ingredient" inManagedObjectContext:insertionContext]; ingredient.name = [thisIngredient objectForKey:@"Name"]; } } NSSet *ingredientsSet = [NSSet ingredientsArray]; [recipe setIngredients:ingredientsSet]; Notes: "setIngredients" is a Core Data generated accessor method. There is a many-to-one relationship between Ingredients and Recipe However, when I run this I get the following error: NSCFDictionary managedObjectContext]: unrecognized selector sent to instance If I remove the last line (i.e. [recipe setIngredients:ingredientsSet];) then, taking a peek at the SQLite database, I see the Recipe and Ingredients have been stored but no relationship has been created between Recipe and Ingredients Any suggestions as to how to ensure the relationship is stored correctly?

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  • Hibernate: Parent/Child relationship in a single-table

    - by Dee
    I hardly see any pointer on the following problem related to Hibernate. This pertains to implementing inheritance using a single database table with a parent-child relationship to itself. For example: CREATE TABLE Employee ( empId BIGINT NOT NULL AUTO_INCREMENT, empName VARCHAR(100) NOT NULL, managerId BIGINT, CONSTRAINT pk_employee PRIMARY KEY (empId) ) Here, the managerId column may be null, or may point to another row of the Employee table. Business rule requires the Employee to know about all his reportees and for him to know about his/her manager. The business rules also allow rows to have null managerId (the CEO of the organisation doesn't have a manager). How do we map this relationship in Hibernate, standard many-to-one relationship doesn't work here? Example code would be appreciated.

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  • Hibernate: Parent/Child relationship in a single-table

    - by Dee
    I hardly see any pointer on the following problem related to Hibernate. This pertains to implementing inheritance using a single database table with a parent-child relationship to itself. For example: CREATE TABLE Employee ( empId BIGINT NOT NULL AUTO_INCREMENT, empName VARCHAR(100) NOT NULL, managerId BIGINT, CONSTRAINT pk_employee PRIMARY KEY (empId) ) Here, the managerId column may be null, or may point to another row of the Employee table. Business rule requires the Employee to know about all his reportees and for him to know about his/her manager. The business rules also allow rows to have null managerId (the CEO of the organisation doesn't have a manager). How do we map this relationship in Hibernate, standard many-to-one relationship doesn't work here? Example code would be appreciated.

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  • Entity Relationship diagram - Composition

    - by GigaPr
    Hi, I am implementing a small database(university Project) and i am facing the following problem. I created a class diagram where i have a class Train {Id, Name, Details} And a class RollingStock which is than generalized in Locomotive and FreightWagon. A train is Composed by multiple RollingStock at a certain time(on different days the rolling stock will compose a different train). I represented the relationship train - rolling stock as a diamond filled (UML) but still I have a many to many relationship between the two tables. so i guess i have to create an additional table to solve the many to many relationship train_RollingStock. but how do i represent the Composition? Can i still use the filled diamond? If yes on which side? Thanks

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  • abstract class extends abstract class in php?

    - by user151841
    I am working on a simple abstract database class. In my usage of this class, I'll want to have some instance be a singleton. I was thinking of having a abstract class that is not a singleton, and then extend it into another abstract class that is a singleton. Is this possible? Recommended?

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  • Foreign key onto weak entity set in MS SQL Server 2008?

    - by Nic Waller
    I'm using Microsoft SQL Server 2008 Management Studio to create a relational schema by following an Entity-Relationship diagram. (included below; unrelated details removed) Until now, primary and foreign keys have been working as expected. But when I try to create a foreign key from the entity relationship takes onto the weak entity set section, I get an error. Section is identified by a composite primary key in the context of course, which has course_id as a primary key. Therefore, the primary key of section is a 4-way composite key. The entity relationship takes needs to refer to section, so it includes all 4 primary attributes from section in it's own primary key. When trying to establish a foreign key relationship from takes to section, Studio gives the following error: The columns in table 'section' do not match an existing primary key or UNIQUE constraint. Am I doing something wrong, or is this an unsupported configuration? I can provide more details or the SQL schema if necessary.

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  • Setting up Eloquent relationships in Laravel for existing InnoDB relationships

    - by adam
    I have an initial migration that sets up two tables (users and projects), with a relationship (innoDB). $table->foreign('user_id')->references('id')->on('users'); I have two Eloquent models set up, blank except for the relationship: return $this->has_many('Project'); Do i definitely need to tell eloquent about the relationship in the models and the database? I'd assumed something as comprehensive as Laravel would infer it from the Schema? Is there something I'm missing?

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  • Core Data - NSPredicate to filter to-many relationship

    - by Macatomy
    I have 2 entities, Task and List. Each task has a to-one relationship to a List object called "list", and there is an inverse relationship with List, which has a to-many relationship with Task called "tasks". I'm trying to use a fetch request with an NSPredicate to get all the Task objects that belong to a specified List: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"list=%@", theList]; [fetchRequest setPredicate:predicate]; (where "theParent" is a reference to a List object). However this returns no fetched objects. If I take out the predicate, then the objects are returned (so I do know they exist, and by NSLogging theList I know it has Task objects associated with it). Thanks

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