public class EmptyStringNullDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser jsonParser, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        JsonNode node = jsonParser.readValueAsTree();
        // 不用考虑null的情况
        String text = node.asText();
        if (text.isEmpty()) {
            return null;
        }
        return text;
    }
}

public class RawJsonDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        // 获取该段json的开始和结束
        int begin = (int) p.getCurrentLocation().getCharOffset();
        p.skipChildren();
        int end = (int) p.getCurrentLocation().getCharOffset();
        // 这里是完整的json字符串，所以截取即可
        String json = p.getCurrentLocation().getSourceRef().toString();
        return json.substring(begin - 1, end);
    }
}