How can I get Jackson to deserialize into my own Array implementation

Question

Given my own array implementation MyArray<T>, how can I make it known to Jackson, so that it is able to deserialize from a JSON Array into MyArray<T>? So far I am only getting this exception:

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of MyArray out of START_ARRAY token

Answer 1

As Dariusz mentioned, it's good to take advantage of the fact that Array class has constructor accepting normal array.

Look, if you use default serializer - your array serialized to JSON would look like:

{"items":["item1","item2"],"size":2,"ordered":true}

it's clearly a waste of space, unless you want size and ordered fields to be preserved.

I suggest you changing the way you serialize your object so that it would look more like normal array, on the other end - deserialization can build Array object again.

If you add following pair of serializer and deserializer:

SimpleModule module = new SimpleModule();
module.addDeserializer(Array.class, new StdDelegatingDeserializer<>(
    new StdConverter<Object[], Array>() {
        @Override
        public Array convert(Object[] value) {
            return new Array(value);
        }
}));

module.addSerializer(Array.class, new StdDelegatingSerializer(
    new StdConverter<Array, Object>() {
        @Override
        public Object convert(Array value) {
            return value.toArray();
        }
}));

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(module);

you will have transparent conversion between these types