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javajsonjacksonpolymorphismdeserialization
vahdet
vahdet

Reputation: 6729

Jackson Polymorphism - Abstract class with no property

I have several Json strings as follows:

{"type1": {"name": "Arnold"}}
{"type2": {"id": "abcd", "job": "plumber"}}

The thing I want to end up with is converting a json string to one of the classes Type1 or Type2 depending on the root property of element:

// Type0 abstract class
public abstract class Type0 {
}

// Type1 class.. convert to it if {"type1": {...}}
@JsonRootName(value = "type1")
public class Type1 extends Type0 {
    @JsonProperty("name")
    String name;
}

// Type2 class.. convert to it if {"type2": {...}} 
@JsonRootName(value = "type2")
public class Type2 extends Type0 {
    @JsonProperty("id")
    String id;

    @JsonProperty("job")
    String job;
}

How to configure the ObjectMapper of Jackson so that I can achieve that deserialization? I think of a logic like the follows, is it doable:

ObjectMapper mapper = new ObjectMapper();
result = mapper.readValue(jsonString, Type0.class);
//TODO: code for deciding whether result is Type1 or Type2 and casting to it

Upvotes: 2

Views: 688

Answers (1)

Manos Nikolaidis
Manos Nikolaidis

Reputation: 22224

Jackson supports such a case with WRAPPER_OBJECT. Annotate the abstract class like this:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.WRAPPER_OBJECT)
@JsonSubTypes({
        @JsonSubTypes.Type(name = "type1", value = Type1.class),
        @JsonSubTypes.Type(name = "type2", value = Type2.class)})
abstract class Type0 {}

and then when parsing Type0.class with readValue you will get an instance of the appropriate derived class. You don't need @JsonRootName over the derived classes.

Upvotes: 2

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