How do you handle polymorphic types in Jackson?
A) By using the @JsonTypeInfo annotation
B) By using the @JsonSubTypes annotation
C) By using the @JsonProperty annotation
D) By using the @JsonIgnoreProperties annotation
Answer:
A) By using the @JsonTypeInfo annotation
Explanation:
In Jackson, you can handle polymorphic types (where an object can be of multiple types) using the @JsonTypeInfo annotation. This annotation allows you to include type information in the JSON output and input, enabling Jackson to deserialize the correct subtype of a polymorphic object.
For example:
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
@JsonSubTypes.Type(value = Cat.class, name = "cat"),
@JsonSubTypes.Type(value = Dog.class, name = "dog")
})
public class Animal { ... }
public class Cat extends Animal { ... }
public class Dog extends Animal { ... }
In this example, the @JsonTypeInfo annotation is used to include a “type” property in the JSON, which helps Jackson determine whether the object should be deserialized as a Cat or a Dog.