杰克逊抽象接口的序列化 [英] Jackson serialization of abstract interface

问题描述

我正在使用一个框架，该框架使用字段supplier(它是抽象接口Supplier<T>)执行类Config的Java Jackson序列化.下面的接口是在框架中定义的，因此我无法更改/添加注释.

I'm working with a framework that performs Java Jackson serialization of class Config with a field supplier that is an abstract interface Supplier<T>. The interfaces below are defined in the framework so I cannot change/add the annotations.

public interface Supplier<T> {
    T get();
}

public interface Calculator {
}

@Data
@NoArgsConstructor
public class Config extends Serializable {
  private Supplier<Calculator> supplier;
}

我有Supplier的具体实现:

class MySupplier implements Supplier {
   @Override Calculator get() { return ...; }
}

当我将Config的实例序列化为JSON时，供应商字段将被序列化而没有类信息.据我了解，这是因为字段声明是抽象的.结果，在反序列化期间，杰克逊不知道如何实例化supplier字段.

When I serialize an instance of Config into JSON the supplier field is serialized without class information. From what I understand this is because the field declaration is abstract. As a result during deserialization Jackson doesn't know how to instantiate supplier field.

"config" : {
 ...
 "supplier" : { }
 ...
}

如何强制实现Supplier接口，以将类名称信息添加到生成的JSON中以允许适当的反序列化?我无权执行执行序列化和反序列化的代码，只能操作Supplier的实现.

How can I force my implementation of the Supplier interface to add class name information into generated JSON to allow proper deserialization? I don't have access to the code that performs serialization and deserialization, I can only manipulate my implementation of Supplier.

推荐答案

Jackson允许使用称为MixIn的功能来配置第三方类.有关更多信息，请阅读:

Jackson allows to configure third party classes using feature called MixIn. For more information read:

1. Jackson Mixin进行救援
2. 杰克逊混入注释

1. Jackson Mixin to the Rescue
2. Jackson Mix-In Annotations

您需要指定两个新接口，以允许您为其他类添加注释:

You need to specify two new interface which will allow you to add annotations for other classes:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME)
@JsonSubTypes({@JsonSubTypes.Type(value = MySupplier.class, name = "MySupplier")})
interface SupplierAnnotations {
}

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME)
@JsonSubTypes({
        @JsonSubTypes.Type(value = MyCalculator.class, name = "MyCalculator"),
        @JsonSubTypes.Type(value = HisCalculator.class, name = "HisCalculator") }
)
interface CalculatorAnnotations {
}

现在，您必须将新课程告知ObjectMapper.您可以通过以下方式做到这一点:

Now, you have to inform ObjectMapper about your new classes. You can do that in this way:

ObjectMapper mapper = new ObjectMapper();
mapper.addMixIn(Calculator.class, CalculatorAnnotations.class);
mapper.addMixIn(Supplier.class, SupplierAnnotations.class);

您需要做的就是列出Suplier和Calculator接口的子类型.

Everything you need to do is to list sub types for Suplier and Calculator interfaces.

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