Make @JsonTypeInfo property optional
- by Mark Peters
I'm using @JsonTypeInfo to instruct Jackson to look in the @class property for concrete type information. However, sometimes I don't want to have to specify @class, particularly when the subtype can be inferred given the context. What's the best way to do that?
Here's an example of the JSON:
{
"owner": {"name":"Dave"},
"residents":[
{"@class":"jacksonquestion.Dog","breed":"Greyhound"},
{"@class":"jacksonquestion.Human","name":"Cheryl"},
{"@class":"jacksonquestion.Human","name":"Timothy"}
]
}
and I'm trying to deserialize them into these classes (all in jacksonquestion.*):
public class Household {
private Human owner;
private List<Animal> residents;
public Human getOwner() { return owner; }
public void setOwner(Human owner) { this.owner = owner; }
public List<Animal> getResidents() { return residents; }
public void setResidents(List<Animal> residents) { this.residents = residents; }
}
public class Animal {}
public class Dog extends Animal {
private String breed;
public String getBreed() { return breed; }
public void setBreed(String breed) { this.breed = breed; }
}
public class Human extends Animal {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
}
using this config:
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@class")
private static class AnimalMixin {
}
//...
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.getDeserializationConfig().addMixInAnnotations(Animal.class, AnimalMixin.class);
Household household = objectMapper.readValue(json, Household.class);
System.out.println(household);
As you can see, the owner is declared as a Human, not an Animal, so I want to be able to omit @class and have Jackson infer the type as it normally would.
When I run this though, I get
org.codehaus.jackson.map.JsonMappingException: Unexpected token (END_OBJECT),
expected FIELD_NAME: missing property '@class' that is to contain type id (for class jacksonquestion.Human)
Since "owner" doesn't specify @class.
Any ideas? One initial thought I had was to use @JsonTypeInfo on the property rather than the type. However, this cannot be leveraged to annotate the element type of a list.
