Ufdjrw

I have a pretty simple Map I want to serialize and deserialize in Jackson, but I can't get it to work.

I have tried the following:

@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);
 

But I get an exception

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.LinkedHashMap out of START_ARRAY token

You need to define/override the fromString() method in TurnKey. Jackson will use toString() to serialize and fromString() to deserialize. That's what "Can not find a (Map) Key deserializer" means in the error message Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not find a (Map) Key deserializer for type [simple type, class no.asgari.civilization.server.model.TurnKey] at com.fasterxml.jackson.databind.deser.DeserializerCache._handleUnknownKeyDeserializer(DeserializerCache.java:584).

A custom KeyDeserializer is not needed.