Java中如何将嵌套对象转换成扁平化的大Map？

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目录+嵌套对象转大Map（扁平化）+Java：JSON扁平化和去扁平化+1. 扁平化数据（网上找的一个JSON大串）+2. Maven依赖+3. 扁平化+4. 去扁平化+嵌套对象转大Map（扁平化）+部分业务场景在传输数据时

目录

• 嵌套对象转大map(扁平化)
• java：JSON扁平化和去扁平化
• 1、扁平化数据(网上找的一json大串)
• 2、maven依赖
• 3、扁平化
• 4、去扁平化

嵌套对象转大map(扁平化)

部分业务场景在传输数据时，需要的数据格式是扁平化的json格式，而在java对象中有时候为了解耦会做一些嵌套（即对象中包含对象，多层也是常有）。

下面的代码可以提供该能力

• 处理单个对象：ObjectToMapUtil.nestedObj2Map
• 处理列表对象：ObjectToMapUtil.nestedObjList2ListMap

package cn.sto.station.twin.common.util; import cn.sto.station.twin.common.util.json.JsonUtil; import com.alibaba.fastjson.JSONObject; import com.alibaba.fastjson.JSON; import lombok.extern.slf4j.Slf4j; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; /** * 基于反射，将obj转为map * * @date 2022-05-30 10:50 */ @Slf4j public class ObjectToMapUtil { private static final String SEPARATOR = "_"; /** * 嵌套对象转大map(扁平化) * * @param object 源对象 * @return map */ public static Map<String, Object> nestedObj2Map(Object object) { Map<String, Object> maps = JSON.parseObject(JSON.toJSONString(object), Map.class); Map<String, Object> result = new HashMap<>(); maps.forEach((key, value) -> { common(maps, result, key, value, key); }); return result; } /** * List嵌套对象转大list map(扁平化) * * @param objectList 源List对象 * @return map */ public static <T> List<Map<String, Object>> nestedObjList2ListMap(List<T> objectList) { ArrayList<Map<String, Object>> resultList = new ArrayList<>(); for (T t : objectList) { resultList.add(nestedObj2Map(t)); } return resultList; } public static Map<String, Object> nestedObj2Map(Map<String, Object> maps, String prefix) { Map<String, Object> result = new HashMap<>(); String keyPrefix = prefix + SEPARATOR; maps.forEach((key, value) -> { String newKey = keyPrefix + key; common(maps, result, key, value, newKey); }); return result; } public static void common(Map<String, Object> maps, Map<String, Object> result, String key, Object value, String newKey) { if (maps.get(key) != null && value instanceof JSONObject) { Map<String, Object> subMaps = (Map) maps.get(key); Map<String, Object> map = nestedObj2Map(subMaps, newKey); if (map != null && !map.isEmpty()) { result.putAll(map); } } else { result.put(newKey, maps.get(key)); } } }

java：JSON扁平化和去扁平化

在github上发现了一个比较好的JSON扁平化和去扁平化处理方法，话不多说，直接开干。

1、扁平化数据(网上找的一json大串)

"{\"type\":10,\"data\":[{\"text\":\"献给爱我们的女神\",\"is_liked\":false,\"index_cover\":\"img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_989_123986672_17737936936133063098.jpg?imageView/2/w/960/q/85\",\"poi\":\"\",\"cover_image_height\":816,\"trip_id\":2387282916,\"index_title\":\"\",\"center_point\":{},\"view_count\":36207,\"location_alias\":\"\",\"cover_image_1600\":\"img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/2/w/1384/h/1384/q/85\",\"cover_image_s\":\"img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/1/w/280/h/280/q/75\",\"share_url\":\"btrip/spot/2387842143/\",\"timezone\":\"Asia/Shanghai\",\"date_tour\":\"2016-06-19T01:19:07+08:00\",\"is_hiding_location\":false,\"user\":{\"location_name\":\"\",\"name\":\"丑到没墙角\",\"resident_city_id\":\"\",\"mobile\":\"\",\"gender\":2,\"avatar_m\":\"img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.m\",\"cover\":\"img.558idc.com/uploadfile/allimg/java/default_user_cover_10.jpg-usercover.display\",\"custom_url\":\"\",\"experience\":{\"value\":59,\"level_info\":{\"name\":\"\",\"value\":1}},\"id\":2384288641,\"birthday\":\"\",\"country_num\":null,\"avatar_s\":\"img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.s\",\"country_code\":null,\"email_verified\":false,\"is_hunter\":false,\"cdc2\":false,\"avatar_l\":\"img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.l\",\"email\":\"\",\"user_desc\":\"\",\"points\":2},\"spot_id\":2387842143,\"is_author\":false,\"cover_image_w640\":\"img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/1/w/640/h/480/q/85\",\"region\":{\"primary\":\"\",\"secondary\":\"\"},\"comments_count\":2,\"cover_image\":\"img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/2/w/960/q/85\",\"cover_image_width\":1088,\"recommendations_count\":21}],\"desc\":\"\"}"

2、maven依赖

github.com/wnameless/json-flattener

 <dependency>      <groupId>com.github.wnameless.json</groupId>      <artifactId>json-flattener</artifactId>      <version>0.8.1</version>  </dependency>

3、扁平化

    /**      * json 扁平化      */     public static void jsonFlatten(String jsonStr) {         JSONObject jsonObj = JSONObject.parseObject(jsonStr);         Map<String, Object> flatMap = JsonFlattener.flattenAsMap(jsonObj.toString());         for (Map.Entry<String, Object> entry : flatMap.entrySet()) {             System.out.println(entry.getKey() + " : " + entry.getValue());         }     }

备注：扁平化级别默认.隔开，若指定级别分割任意符号：

 new JsonFlattener(jsonObj.toString()).withSeparator(',').flattenAsMap();

输出结果：

data[0].center_point: {}
data[0].comments_count: 2
data[0].cover_image: img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/2/w/960/q/85
data[0].cover_image_1600: img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/2/w/1384/h/1384/q/85
data[0].cover_image_height: 816
data[0].cover_image_s: img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/1/w/280/h/280/q/75
data[0].cover_image_w640: img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_926_123986672_17737936923172662193.jpg?imageView/1/w/640/h/480/q/85
data[0].cover_image_width: 1088
data[0].date_tour: 2016-06-19T01:19:07+08:00
data[0].index_cover: img.558idc.com/uploadfile/allimg/java/photo_d_2016_06_19_01_21_20_989_123986672_17737936936133063098.jpg?imageView/2/w/960/q/85
data[0].index_title:
data[0].is_author: false
data[0].is_hiding_location: false
data[0].is_liked: false
data[0].location_alias:
data[0].poi:
data[0].recommendations_count: 21
data[0].region.primary:
data[0].region.secondary:
data[0].share_url: btrip/spot/2387842143/
data[0].spot_id: 2387842143
data[0].text: 献给爱我们的女神
data[0].timezone: Asia/Shanghai
data[0].trip_id: 2387282916
data[0].user.avatar_l: img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.l
data[0].user.avatar_m: img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.m
data[0].user.avatar_s: img.558idc.com/uploadfile/allimg/java/avatar_41_b8_aedfd71640e3ec09d0c30edc47df04dc56dbf38a.jpg-avatar.s
data[0].user.birthday:
data[0].user.cdc2: false
data[0].user.cover: img.558idc.com/uploadfile/allimg/java/default_user_cover_10.jpg-usercover.display
data[0].user.custom_url:
data[0].user.email:
data[0].user.email_verified: false
data[0].user.experience.level_info.name:
data[0].user.experience.level_info.value: 1
data[0].user.experience.value: 59
data[0].user.gender: 2
data[0].user.id: 2384288641
data[0].user.is_hunter: false
data[0].user.location_name:
data[0].user.mobile:
data[0].user.name: 丑到没墙角
data[0].user.points: 2
data[0].user.resident_city_id:
data[0].user.user_desc:
data[0].view_count: 36207
desc:
type: 10

4、去扁平化

String unflattenJson = JsonUnflattener.unflatten(flattenJson);

以上为个人经验，希望能给大家一个参考，也希望大家多多支持自由互联。