Suppose I have the following class hierarchy and Jackson annotations.
@JsonTypeInfo(use=JsonTypeInfo.Id.CLASS
public class Base {
private int value;
// snipped getter and setter for "value" field
}
public class Foo extends Base {
}
public class Bar extends Base {
}
I would like to be able to perform all of the following deserialization
cases:
// these both work
Foo foo1 = new ObjectMapper().readValue("{\"@class\": \"Foo\", \"value\":
1}", Base.class)
Foo foo2 = new ObjectMapper().readValue("{\"@class\": \"Foo\", \"value\":
1}", Foo.class)
// so does these
Bar bar1 = new ObjectMapper().readValue("{\"@class\": \"Bar\", \"value\":
1}", Base.class)
Bar bar2 = new ObjectMapper().readValue("{\"@class\": \"Bar\", \"value\":
1}", Bar.class)
// these two fail,
with com.fasterxml.jackson.databind.JsonMappingException: Unexpected token
(END_OBJECT), expected FIELD_NAME: missing property '@class' that is to
contain type id
Foo foo2 = new ObjectMapper().readValue("{\"value\": 1}", Foo.class)
Bar bar2 = new ObjectMapper().readValue("{\"value\": 1}", Bar.class)
Ideally, the last two cases should still work. Even though the String
content does not contain the type ID field (the default of @class in this
case), the deserializer should still be able to make use of the fact that I
explicitly requested the class in the readValue calls, via the valueType
parameter (Foo.class and Bar.class respectively).
Is it possible to configure the deserializer to work in this way? I read
through the Wiki page on polymorphic deserialization
<https://github.com/FasterXML/jackson-docs/wiki/JacksonPolymorphicDeserialization>
a few times but couldn't figure out how to approach this. I suspect it
involves making use of @JsonTypeResolver and/or @JsonTypeIdResolver, but
I'm not sure. Any tips on how to proceed are greatly appreciated.
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