java - jsonvalue - objectmapper jackson

Serializar/Deserializar mapa personalizado<Key, Object> en Jackson

Question

Tengo un mapa bastante simple que quiero serializar y deserializar en Jackson, pero no puedo hacerlo funcionar.

He probado lo siguiente:

@JsonSerialize(keyUsing=TurnKeySerializer.class)
@JsonDeserialize(keyUsing = TurnKeyDeserializer.class)
Map<TurnKey, PlayerTurn> publicTurns = new TreeMap<>();
@JsonIgnoreProperties(ignoreUnknown = true)
@Data //Creates Getter/Setter etc
public class TurnKey implements Comparable<TurnKey> {
private final int turnNumber;
private final String username;
public TurnKey(int turnNumber, String username) {
this.turnNumber = turnNumber;
this.username = username;
}
@Override
public int compareTo(TurnKey o) {
int v = Integer.valueOf(turnNumber).compareTo(o.getTurnNumber());
if (v != 0) {
return v;
}
return username.compareTo(o.getUsername());
}
@Override
public String toString() {
return "{" +
"turnNumber:" + turnNumber +
", username:''" + username + "''" +
"}";
}
public class TurnKeySerializer extends JsonSerializer<TurnKey> {
@Override
public void serialize(TurnKey value, JsonGenerator gen, SerializerProvider serializers) throws IOException, JsonProcessingException {
if (null == value) {
throw new IOException("Could not serialize object to json, input object to serialize is null");
}
StringWriter writer = new StringWriter();
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(writer, value);
gen.writeFieldName(writer.toString());
}
}
public class TurnKeyDeserializer extends KeyDeserializer {
private static final ObjectMapper mapper = new ObjectMapper();
@Override
public TurnKey deserializeKey(String key, DeserializationContext ctxt) throws IOException, JsonProcessingException {
return mapper.readValue(key, TurnKey.class);
}
}

Pero recibo una excepción

com.fasterxml.jackson.databind.JsonMappingException: no se puede deserializar la instancia de java.util.LinkedHashMap con el token START_ARRAY