inheritance

问题 I'm wondering whether it is possible to add additional functionality to the @Column annotation in JPA. Specifically, what I would like to do is tag columns of sensitive data with an @ProtectedColumn annotation: this would then tell the persistence framework to apply some type of data protection (encryption, tokenization, whatever...) to the values when storing them into the actual data store, and then reverse that process when reading the values from the data store. So I might have a Customer

问题 I have a class called cache. It is an generic, abstract class responsible for handling the global cache for forever type extends the class. My question is, if I have a static variable under the base class, will the static variable be unique per extending type or will it be the same for all types that extend Cache. For example the interface: Cache<K, V> private static Cache<K, V> [creates a cache store on first load] static V get(K key); Then I have an implementing class: PersonCache extends

问题 I'm writing a method supposed to retrieve all annotations of a specific method declaring class and its superclasses. By using the method getAnnotations() on the declaring class, the resulting table contains only the declaring class annotations and the superclass annotations are ignored. If I remove the annotations of the declaring class, then the superclass annotation are present. What am I missing here? The simplified method retrieving the annotations : public void check(Method invokedMethod

问题 A use case of the super() builtin in python is to call an overridden method. Here is a simple example of using super() to call Parent class's echo function: class Parent(): def echo(self): print("in Parent") class Child(Parent): def echo(self): super().echo() print("in Child") I've seen code that passes 2 parameters to super() . In that case, the signature looks somehing like super(subClass, instance) where subClass is the sub class calling super() from, and instance is the instance the call

问题 I'm not sure whether this is possible in EF, but I am creating a bunch of classes and am trying to get EF to create the tables for me. Now EF creates my tables fine, except for a minor issue. It created the tables as: Person - PersonId (PK) Foo - PersonId (PK) - FooId (INT) Poo - PersonId (PK) - PooId (INT) Ideally, I want the PersonId in tables Foo and Poo to be a foreign key not as the primary key. Is this possible? Tried using the ModelBuilder to do this via: modelBuilder.Entity<Foo>()

问题 For a project I am looking at a case where the following situation exists. There is a class foo which requires an identifying number x when constructed. So its constructor argument looks something like foo(x). Now I want to derive a class based on foo, called bar, which will basically hold two foo's internally and to the outside world acts as a single foo. The way I want to do this is by use of two constructor arguments y and z for bar, which will then, in the constructor, generate foo(y) and

问题 Related question: Standard-layout and tail padding Snippet: #include <iostream> #include <type_traits> struct A0 { int a; char c; }; struct B0 : A0 { char d; }; struct A1 { int a; private: char c; }; struct B1 : A1 { char d; }; struct A2 { private: int a; char c; }; struct B2 : A2 { char d; }; int main() { std::cout << std::is_pod<A0>::value << ' ' << sizeof(B0) << std::endl; // 1 12 std::cout << std::is_pod<A1>::value << ' ' << sizeof(B1) << std::endl; // 0 8 std::cout << std::is_pod<A2>:

问题 An interesting problem. I'm building an application using Symfony 2 and I'm trying to get Doctrine to auto-generate my schema from my entity classes. I have two entity classes, Invoice and CreditNote . CreditNote extends Invoice . They look like this - Invoice.php - namespace My\Bundle\BillingBundle\Entity; use Doctrine\ORM\Mapping as ORM; /** * @ORM\Entity * @ORM\Table(name="invoice") * @ORM\InheritanceType("SINGLE_TABLE") * @ORM\DiscriminatorColumn(name="discriminator", type="string") *

问题 I'm trying to duplicate and then modify a class programmatically but I'm running into problems with python 3's magic super for example the following class Base(): def __init__(self): print("Base init") class Orginal(Base): def __init__(self): super().__init__() print("Orginal init") Modified = type(Orginal.__name__, Orginal.__bases__, dict(Orginal.__dict__)) Modified.f = lambda self: print("f") m = Modified() raises TypeError: super(type, obj): obj must be an instance or subtype of type So I

问题 I'm trying to duplicate and then modify a class programmatically but I'm running into problems with python 3's magic super for example the following class Base(): def __init__(self): print("Base init") class Orginal(Base): def __init__(self): super().__init__() print("Orginal init") Modified = type(Orginal.__name__, Orginal.__bases__, dict(Orginal.__dict__)) Modified.f = lambda self: print("f") m = Modified() raises TypeError: super(type, obj): obj must be an instance or subtype of type So I