Java: Jackson polymorphic JSON deserialization of an object with an interface property?

Question

I am using Jackson's `ObjectMapper` to deserialize a JSON representation of an object that contains an interface as one of its properties. A simplified version of the code can be seen here: https://gist.github.com/sscovil/8735923 Basically, I have a class `Asset` with two properties: `type` and `properties`. The JSON model looks like this: ``` { "type": "document", "properties": { "source": "foo", "proxy": "bar" } } ``` The `properties` property is defined as an interface called `AssetProperties`, and I have several classes that implement it (e.g. `DocumentAssetProperties`, `ImageAssetProperties`). The idea is that image files have different properties (height, width) than document files, etc. I've worked off of the examples in this article, read through docs and questions here on SO and beyond, and experimented with different configurations in the `@JsonTypeInfo` annotation parameters, but haven't been able to crack this nut. Any help would be greatly appreciated. Most recently, the…

Accepted Answer

You should use `JsonTypeInfo.As.EXTERNAL_PROPERTY` instead of `JsonTypeInfo.As.PROPERTY`. In this scenario your `Asset` class should look like this:

```
class Asset {

@JsonTypeInfo(
            use = JsonTypeInfo.Id.NAME,
            include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
            property = "type")
    @JsonSubTypes({
        @JsonSubTypes.Type(value = ImageAssetProperties.class, name = "image"),
        @JsonSubTypes.Type(value = DocumentAssetProperties.class, name = "document") })
    private AssetProperties properties;

public AssetProperties getProperties() {
        return properties;
    }

public void setProperties(AssetProperties properties) {
        this.properties = properties;
    }

@Override
    public String toString() {
        return "Asset [properties("+properties.getClass().getSimpleName()+")=" + properties + "]";
    }
}
```

See also my answer in this question: Jackson JsonTypeInfo.As.EXTERNAL_PROPERTY doesn't work as expected.

Java: Jackson polymorphic JSON deserialization of an object with an interface property?

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