Jackon JSON：子类未知时的多态解除(Jackon JSON: Polymorphic deseralization when subclasses are unknown)

 我正在尝试使用Jackson对JSON进行一些多态的deseralization，但是子类列表在编译时是未知的，所以我不能在基类上使用@JsonSubtype注释。 相反，我想使用TypeIdResolver类来执行与属性值的转换。 
 
 我可能遇到的可能子类列表将是动态的，但它们都是在运行时使用注册表注册的。 所以我似乎需要我的TypeIdResolver对象来引用该注册表类。 它必须在基本上是一个依赖注入环境中运行（即我不能有TypeIdResolver参考的单例类），所以我认为我需要将注册表类注入TypeIdResolver。 我认为我想写的代码是： 
 
ObjectMapper mapper = new ObjectMapper();
mapper.something(new MyTypeIdResolver(subclassRegistry));
mapper.readValue(...)
 
 但是，我找不到在中间做位的方法。 我能找到的唯一方法是使用java注释来指定TypeIdResolver将是什么。 
 
 这个问题有没有办法在mapper配置而不是注释上指定@JsonTypeIdResolver？ 是相同的，虽然动机不同，答案是使用注释mixin，这在这里不起作用。 

I'm trying to do some polymorphic deseralization of JSON using Jackson, however the list of subclasses is unknown at compile time, so I can't use a @JsonSubtype annotation on the base class. Instead I want to use a TypeIdResolver class to perform the conversion to and from a property value.
 
The list of possible subclasses I might encounter will be dynamic, but they are all registered at run time with a registry. So I would appear to need my TypeIdResolver object to have a reference to that registry class. It has to operate in what is essentially a dependency injection environment (i.e I can't have a singleton class that the TypeIdResolver consults), so I think I need to inject the registry class into the TypeIdResolver. The kind of code I think I want write is:
 
ObjectMapper mapper = new ObjectMapper();
mapper.something(new MyTypeIdResolver(subclassRegistry));
mapper.readValue(...)
 
However, I can't find a way of doing the bit in the middle. The only methods I can find use java annotations to specify what the TypeIdResolver is going to be.
 
This question Is there a way to specify @JsonTypeIdResolver on mapper config instead of annotation? is the same, though the motivation is different, and the answer is to use an annotation mixin, which won't work here.

原文：https://stackoverflow.com/questions/37793134