Jackson多态性：如何将多个子类型映射到同一个类 [英] Jackson polymorphism: How to map multiple subtypes to the same class

问题描述

我正在使用Jackson 1.9.x.
坚持动物示例，这是我想做的事情：

I'm using Jackson 1.9.x. Sticking with the Animals example, Here's what I'd like to do:

假设我有一个Animal类：

Let's say I have an Animal class:

public class Animal {
    private String type;
    // accessors
}

public class Mammal extends Animal {
    private String diet;
    // accessors
}

public class Bird extends Animal {
    private boolean tropical;
    // accessors
}

我希望能够做点什么像这样（我将一些子类型映射到一个类，并将一些子类型映射到另一个类）：

I would like to be able to do something like this (where I map a few subtypes to one class, and a few more to a different class):

@JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = "type")
@JsonSubTypes({@JsonSubTypes.Type(value = Mammal.class, name = "Dog"),
                @JsonSubTypes.Type(value = Mammal.class, name = "Cat"),
                @JsonSubTypes.Type(value = Bird.class, name = "Dodo"},
                @JsonSubTypes.Type(value = Bird.class, name = "Cockatoo"})
public class Animal {

}

我现在看到的是Jackson只会识别Dog-to-Mammal和Dodo-to-Bird映射。这是因为StdSubtypeResolver._collectAndResolve（）只允许同一个类进行注册一次（由于NamedType.equals（）的实现）。

What I'm seeing right now is that Jackson will only recognize the Dog-to-Mammal and the Dodo-to-Bird mapping. This is because StdSubtypeResolver._collectAndResolve() only allows the same class to get registered once (due to the implementation of NamedType.equals()).

我是否有解决方法？我看到了吗？

Is there a workaround to the issue I'm seeing?

推荐答案

也许不是通过使用注释。问题来自于这样的映射不适用于序列化，并且现有映射确实期望一对一（双射）关系。
但您可能想在 jackson-databind问题跟踪器上提交RFE;可能会增加支持。

Perhaps not by using annotations. Problems comes from the fact that such mapping would not work for serialization, and existing mapping does expect one-to-one (bijection) relationship. But you may want to file an RFE at jackson-databind issue tracker; adding support may be possible.

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