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 MessagePack
    ObjectMapper objectMapper = new ObjectMapper(new MessagePackFactory());

    Map<Integer, MessageData> map = new HashMap<>();
    MessageData messageData = new MessageData();

    // Element A in MAP
    messageData.setUuid(UUID.randomUUID().toString());
    messageData.setName("CWIKI.US - A");
    map.put(uuid_a, messageData);

    // Element B in MAP
    messageData = new MessageData();
    messageData.setUuid(UUID.randomUUID().toString());
    messageData.setName("CWIKI.US - B");
    map.put(uuid_b, messageData);


    try {
        // Serialize a Java object to byte array
        bytes = objectMapper.writeValueAsBytes(map);
        logger.debug("Length of Bytes: [{}]", bytes.length);

        // Deserialize the byte array to a MAP
        Map<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