以嵌套方式使用多个@JsonSubType注释

问题描述

是否可以嵌套使用多个@JsonSubType注释？

例如，设想以下类别：

@Data
@JsonSubTypeInfo(include=As.EXISTING_PROPERTY, property="species", use=Id.NAME, visible=true)
@JsonSubTypes({
  @Type(name="Dog", value=Dog.class)
  @Type(name="Cat", value=Cat.class)
})
public abstract class Animal {
  private String name;
  private String species;
}

@Data
@JsonSubTypeInfo(include=As.EXISTING_PROPERTY, property="breed", use=Id.NAME, visible=true)
@JsonSubTypes({
  @Type(name="Labrador", value=Labrador.class)
  @Type(name="Bulldog", value=Bulldog.class)
})
public abstract class Dog {
  private String breed;
}

@Data
public class Labrador extends Dog {
  private String color;
}

@Data
public class Bulldog extends Dog {
  private String type; // "frenchy", "english", etc..
}

如果使用对象映射器，我可以成功地将Bulldog映射到JSON，但是，当尝试读取生成的JSON并将其读回时，会出现类似以下的错误：

Can not construct instance of com.example.Dog abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information

是否有可能让Jackson进行此类分型？我需要为每个子类创建一个自定义反序列化器吗？

思路：

如果我使用@JsonTypeInfo和与您类似的设置，则以下工作。也许您的问题出在反序列化代码中，所以请查看以下内容：以嵌套方式使用多个@JsonSubType注释

public class MyTest {

    @Test
    public void test() throws IOException {
        final Bulldog bulldog = new Bulldog();
        bulldog.setBreed("Bulldog");
        bulldog.setType("B-Dog");

        final ObjectMapper om = new ObjectMapper();
        final String json = om.writeValueAsString(bulldog);
        final Dog deserialized = om.readValue(json, Dog.class);
        assertTrue(deserialized instanceof Bulldog);

    }

    @JsonTypeInfo(include = As.EXISTING_PROPERTY, property = "species", use = Id.NAME, visible = true)
    @JsonSubTypes({
            @Type(name = "Dog", value = Dog.class),
            @Type(name = "Cat", value = Cat.class)
    })

    public static abstract class Animal {

        private String name;
        private String species;
    }

    @JsonTypeInfo(include = As.EXISTING_PROPERTY, property = "breed", use = Id.NAME, visible = true)
    @JsonSubTypes({
            @Type(name = "Labrador", value = Labrador.class),
            @Type(name = "Bulldog", value = Bulldog.class)
    })
    public static abstract class Dog {

        private String breed;

        public String getBreed() {
            return breed;
        }

        public void setBreed(final String breed) {
            this.breed = breed;
        }
    }

    public static abstract class Cat {

        private String name;
    }

    public static class Labrador extends Dog {

        private String color;

        public String getColor() {
            return color;
        }

        public void setColor(final String color) {
            this.color = color;
        }
    }

    public static class Bulldog extends Dog {

        private String type; // "frenchy", "english", etc..

        public String getType() {
            return type;
        }

        public void setType(final String type) {
            this.type = type;
        }
    }
}

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