Cannot construct instance of - Jackson

Question

I am using Jackson and I'm having problems, when I try to deserialize an Object I get the following error:

com.fasterxml.jackson.databind.JsonMappingException:      Can not construct instance of net.MyAbstractClass,      problem: abstract types either need to be mapped to concrete types,          have custom deserializer, or be instantiated with additional type information 

I am having problems in the attribute:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.WRAPPER_OBJECT, property = "@id") @JsonSubTypes({ @JsonSubTypes.Type(value = MyAbstractClass.class, name = "MyAbstractClass") }) @ManyToOne private MyAbstractClass object; 

Could anyone help me?

Answer 1

You cannot instantiate an abstract class, Jackson neither. You should give Jackson information on how to instantiate MyAbstractClass with a concrete type.

See this answer on stackoverflow: Jackson JSON library: how to instantiate a class that contains abstract fields

And maybe also see Jackson Polymorphic Deserialization

Answer 2

You need to use a concrete class and not an Abstract class while deserializing. if the Abstract class has several implementations then, in that case, you can use it as below-

  @JsonTypeInfo( use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")     @JsonSubTypes({        @Type(value = Bike.class, name = "bike"),        @Type(value = Auto.class, name = "auto"),        @Type(value = Car.class, name = "car")     })     public abstract class Vehicle {         // fields, constructors, getters, setters     }