Skipping nested field with Jackson data binding?

Question

How must I bind (bidirectional) the following json snippet to the Java objects below with Jackson?

I want the key/value pairs of the Json newsletter node to end up in the Map of the newsletter field. What must be the Jackson config (annotations and others) to bind this ? Sorry, I don't know how :( (using the latest version of Jackson).

The Json format below is fixed, I receive it from a third party rest service (I can't change it). I can change the java code, but prefer the setup below.

JSON:

{
    "newsletter": {
        "key1": "value1",
        "key2": "value2",
        "key3": "value3"
    }
}

The Java Objects:

class Preferences {
    private NewsLetter newsLetter;
    // getter/setter for field newsLetter.
}

class NewsLettter {
    private Map<String, String> properties;
    // getter/setter for field properties.
}

Answer 1

You could simply use @JsonAnySetter for deserialization

Marker annotation that can be used to define a non-static, two-argument method (first argument name of property, second value to set), to be used as a "fallback" handler for all otherwise unrecognized properties found from JSON content.

And @JsonAnyGetter for serialization.

Marker annotation that can be used to define a non-static, no-argument method or member field as something of a reverse of JsonAnySetter method; basically being used like a getter but such that contents of the returned Map (type must be Map) are serialized as if they were actual properties of the bean that contains method/field with this annotations

public class Newsletter {

    private final Map<String, String> properties = new HashMap<>();

    @JsonAnySetter
    public void addProperty(String name, String value) {
        properties.put(name, value);
    }

    @JsonAnyGetter
    public Map<String, String> getProperties() {
        return properties;
    }
}

This should work just fine for your use case.

Test

public class Main {

    public static void main(String[] args) throws Exception {
        String json
                = "{\n"
                + "    \"newsletter\": {\n"
                + "        \"key1\": \"value1\",\n"
                + "        \"key2\": \"value2\",\n"
                + "        \"key3\": \"value3\"\n"
                + "    }\n"
                + "}";

        ObjectMapper mapper = new ObjectMapper();
        Preferences prefs = mapper.readValue(json, Preferences.class);
        Map<String, String> properties = prefs.getNewsletter().getProperties();
        for (Map.Entry<String, String> prop: properties.entrySet()) {
            System.out.println(prop.getKey() + ":" + prop.getValue());
        }
    }
}

See Also:

• Jackson tips: using @JsonAnyGetter/@JsonAnySetter to create "dyna beans"