JSON mapping polymorphism support

#javaee saturday, march 19, 2016

JSR 367 or JSONB is currently developed to enable Java object to JSON mapping. When deserializing JSON it may be neccessary in some situations to determine polymorph type information from the serialized JSON.

Consider the following example:

public class Test {
    private List<Customer> customers;
}

public class Customer {
    private String name;
}

public class VipCustomer {
    // same properties, overridden methods
}

The serialized JSON may look like follows — note that the type information whether the list contains Customers or VipCustomers is lost.

{
    "customers": [
        {
            "name": "John"
        },{
            "name": "Doe"
        }
    ]
}

Therefore a specific type property could be included.

{
    "customers": [
        {
            "//javaType": "a.b.c.Customer",
            "name": "John"
        },{
            "//javaType": "a.b.c.VipCustomer",
            "name": "Doe"
        }
    ]
}

In order to include such functionality in JSONB a new @JsonbTypeInfo annotation — with //jsonInfo as default property name and possible overrides — could be defined.

Feedback is highly welcome.

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