inheritance

问题 Take the situation listed in this question: Mapping multi-Level inheritance in Hibernate How would this mapping be done with Annotations rather than an hbm file? 回答1: What specifically are you having trouble with? Mapping class hierarchy via joined subclasses is pretty straightforward: @Entity @Inheritance(strategy=InheritanceType.JOINED) public class A implements Serializable { ... } @Entity public class B extends A { ... } @Entity @PrimaryKeyJoinColumn(name="A_ID") public class C extends A

问题 I'm using Spring Framework transactional annotations for transaction managing and I have an abstract class annotated @Transactional as seen below: package org.tts.maqraa.service; import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.Set; import javax.persistence.EntityManager; import javax.persistence.EntityNotFoundException; import javax.persistence.PersistenceContext; import javax.persistence.PersistenceContextType; import javax.persistence.Query;

问题 I'm going to use Entity Framework soon for a Booking System ( made from scratch ). I have been doing a few Prototypes, trying to figure out what I want to do before the project is started (I'm still discussing requirements etc. with the client). Consider this case: I have a Booking, and a booking can have associated Ressources, that can be booked, but these ressource can be different, and have different Fields etc. I have never really used EF before, so I don't know how I can achieve this

问题 I'm trying to find the actual class of a django-model object, when using model-inheritance. Some code to describe the problem: class Base(models.model): def basemethod(self): ... class Child_1(Base): pass class Child_2(Base): pass If I create various objects of the two Child classes and the create a queryset containing them all: Child_1().save() Child_2().save() (o1, o2) = Base.objects.all() I want to determine if the object is of type Child_1 or Child_2 in basemethod, I can get to the child

问题 I’m building a Laravel application that involves tracking different types of leads. For example, there are Refinance leads and Purchase leads . Since the leads share a lot of information and functionality, but not all, my thinking was to create a Lead class, which extends Laravel’s Model class, and then a RefinanceLead class, which extends the Lead class. So I’d have: class Lead extends Model { // shared lead stuff } class RefinanceLead extends Lead { // stuff specific to refinance leads } My

问题 The following code in java, when run on elipse, gives same output even if we replace superclass s=new sub(); with, sub s= new sub(); Note that we have overridden methods. Output is: changed supermethod in sub class num is sub class 5 Code: public class superclass { int num=2; public static void main(String str[]){ superclass s=new sub(); //HERE: nothing changes if we write, sub s=new sub(); s.supermethod(); s.method(); } void supermethod(){ System.out.println("supermethod as in superclass");

问题 I'm Java person who just started learning Python. Take this example: class Person(): def __init__(self, name, phone): self.name = name self.phone = phone class Teenager(Person): def __init__(self, name, phone, website): self.name=name self.phone=phone self.website=website I'm sure there's a lot of redundant code (I know in Java, there are a lot of redundancies for the bit of code above). Which parts are redundant with respect to which attributes are already inherited from the parent class?

问题 I have a base service and two inhering services: @Injectable({ providedIn: 'root' }) export class BaseService { foo(src?: string){ return `speaking from ${src || 'BaseService'}`; } } @Injectable({ providedIn: 'root' }) export class SomeService extends BaseService { foo(){ return super.foo('SomeService') } } @Injectable({ providedIn: 'root' }) export class AnotherService extends BaseService { foo(){ return super.foo('AnotherService') } } I wish to inject them in some component and retrieve

问题 I write quite a lot of code which processes message protocols. Quite often a message protocol will have a generic message frame which can be deserialised from a serial port or socket; the frame contains a message type, and the message payload must be processed based on the message type. Normally I write a polymorphic set of classes with accessor methods and a constructor which takes a reference to the message frame. It occurs to me though that instead of constructing an accessor class based

问题 I have two classes, Staff and AdvancedStaff , which extends the former. Staff has this constructor: public Staff (String number, String title, String name, String role, char level) { staffNumber = number; staffTitle = title; staffName = name; staffRole = role; payScaleLevel = level; } I'll note that all instance variables have been set to private. While, Advanced Staff has this constructor: public AdvancedStaff (String number, String title, String name) { super(number, title, name); role =