java - Spring @RequestBody containing a list of different types (but same interface)

Question

Let's say that I have a domain class :

    public class Zoo{
        private List<Animal> animals;
        ....

where an Animal is an interface with different implementations (Cat,Dog). Let's say that I want to be able to save a Zoo object :

    @RequestMapping(value = "/zoo", method = RequestMethod.POST)
    public @ResponseBody void save(@RequestBody Zoo zoo) {
    ....

and I want to send a json - something like :

    {
        animals:[
            {type:'Cat', whiskers-length:'3'},
            {type:'Dog', name:'Fancy'}
        ]
    }

How can I tell spring MVC to map animal to Cat type when type=='Cat' and to map it to a Dog class when type=='Dog'?

Answer 1

You should use the Jackson annotations @JsonTypeInfo and @JsonSubTypes to achieve polymorphic json. The annotations go on the Animal base class.

@JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = "type")
@JsonSubTypes({@JsonSubTypes.Type(value = Dog.class, name = "Dog"),
        @JsonSubTypes.Type(value = Cat.class, name = "Cat")})
public abstract class Animal {

}