Java将对象转为Map，可以采用四种方法，最后一种令人拍案称奇

ObjectMapper mapper = new ObjectMapper();
User user = new User();
String jsonInString = mapper.writeValueAsString(user);
Map<?, ?> mapRepresentation = mapper.readValue(jsonInString, Map.class);
System.out.println(mapRepresentation);

Gson gson = new Gson();
User user = new User();
Type targetType = new TypeToken<Map<String, Object>>(){}.getType();
Map<String, Object> mapRepresentation = gson.fromJson(gson.toJson(user), targetType);
System.out.println(mapRepresentation);

User user = new User();

Map<String, Object> mapRepresentation = Maps.newHashMap();
for (Field field : user.getClass().getDeclaredFields()) {
    field.setAccessible(true);
    mapRepresentation.put(field.getName(), field.get(user));
}

System.out.println(mapReflection);

User user = new User();
Map<String, Object> mapRepresentation = BeanUtil.beanToMap(user);
System.out.println(mapRepresentation);