convert JSON String to Object.class and use instanceof to determine actual class

I've got a question similar to the one asked here:

Convert JSON string to “Object.class”

I'd like to do this without

@JsonTypeInfo(include=As.PROPERTY, use=Id.CLASS, property="class")

on all the classes I wish to serialize/deserialize to/from JSON.

I'd like to do something like:

Object o = mapper.readValue(*a JSON string*, Object.class);

if (o instance of *foo.bar.SomeClass*){

    foo.bar.SomeClass fb = (foo.bar.SomeClass)o

                   *or*

    foo.bar.SomeClass fb = mapper.readValue(*a JSON string*, foo.bar.SomeClass);    }

Is that at all possible?