当你希望在 Map 中不使用 String 为 Key，那么你需要使用 MessagePackKeySerializer 来为 key 进行序列化。

本测试方法，可以在 https://github.com/cwiki-us-demo/serialize-deserialize-demo-java/blob/master/src/test/java/com/insight/demo/serialize/MessagePackSerializer.java 中找到。

/*** testMessagePackSerializationMapKey*/
@Test
@JsonSerialize(keyUsing = MessagePackKeySerializer.class)
public void testMessagePackSerializationMapKey() {logger.debug("testMessagePackSerializationNotCloseInputStream");byte[] bytes = new byte[0];Integer uuid_a = 101;Integer uuid_b = 102;// Instantiate ObjectMapper for MessagePackObjectMapper objectMapper = new ObjectMapper(new MessagePackFactory());Map<Integer, MessageData> map = new HashMap<>();MessageData messageData = new MessageData();// Element A in MAPmessageData.setUuid(UUID.randomUUID().toString());messageData.setName("CWIKI.US - A");map.put(uuid_a, messageData);// Element B in MAPmessageData = new MessageData();messageData.setUuid(UUID.randomUUID().toString());messageData.setName("CWIKI.US - B");map.put(uuid_b, messageData);try {// Serialize a Java object to byte arraybytes = objectMapper.writeValueAsBytes(map);logger.debug("Length of Bytes: [{}]", bytes.length);// Deserialize the byte array to a MAPMap<String, MessageData> deserialized = objectMapper.readValue(bytes, new TypeReference<Map<Integer, MessageData>>() {});logger.debug("Deserialized MAP Count: [{}]", deserialized.size());logger.debug("MAP index 0: [{}]", deserialized.get(uuid_a).getName());assertEquals("CWIKI.US - A", deserialized.get(uuid_a).getName());} catch (JsonProcessingException ex) {logger.error("Serialize Error", ex);} catch (IOException e) {e.printStackTrace();}
}

https://www.cwiki.us/display/Serialization/MessagePack+Jackson+Dataformat