Java泛型.如何正确扩展可扩展通用抽象参数类型的类的参数类型的类 [英] Java Generics. How to properly extend parameter typed class that extends Generic abstract parameter typed class

问题描述

我有泛型抽象超类 GenericModel ，该类具有我想在子类中调用的方法，如下所示:

I have generic abstract superclass GenericModel with method that I would like to call in children classes as follow:

public abstract class GenericModel<T extends GenericModel> {
    @Transient protected Class<T> entityClass;
    public GenericModel() {
    Class obtainedClass = getClass();
    Type genericSuperclass = null;
    for(;;) {
        genericSuperclass = obtainedClass.getGenericSuperclass();
        if(genericSuperclass instanceof ParameterizedType) {
            break;
        }
        obtainedClass = obtainedClass.getSuperclass();
    }
    ParameterizedType genericSuperclass_ = (ParameterizedType) genericSuperclass;
    entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0]));

    // some code

    public List<T> getByCreationUser_Id(Long id) {
        // method body
        return entities;
    }
}

我正在用以下方法扩展该类:

I am extending class this class with:

public class Insurance extends GenericModel<Insurance> {
     // some code
}

我想扩展该类的内容:Insurance，如下所示:

And I wanna extend class: Insurance with this class as follow:

public class Liability extends Insurance {

}

和Liability类的对象，我想调用方法: getByCreationUser_Id()，而不是T列表，我想获得List<Liability>如下:

and object of Liability class I would like call method: getByCreationUser_Id() and instead of list of T I would like to get List<Liability> as follow:

List<Liability> currentUserInsurances = new Liability().getByCreationUser_Id(1L);

不幸的是，我遇到一个错误:

Unfortunatelly I am getting an error:

Type mismatch: cannot convert from List<Insurance> to List<Liability>

当我在保险类上调用相同的方法时，它会起作用: List<Insurance>

When I will call same method on Insurance class it works, I am getting an: List<Insurance>

我已经尝试过声明类，如下所示:

I've already tried declare classes as follow:

public class Insurance<T> extends GenericModel<Insurance<T>> {}
public class Liability extends Insurance<Liability> {}

但是id不起作用.发生编译错误.

But id doesn't work. Compile errors occur.

请帮助.

推荐答案

您需要将Insurance类声明为

public class Insurance<T extends Insurance> extends GenericModel<T> {}

然后，您的Liability类为

public class Liability extends Insurance<Liability> {}

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