详解Java中String JSONObject JSONArray List转换

JSON使用阿里的fastJson为依赖包

gradle依赖管理如下：

compile group: 'com.alibaba', name: 'fastjson', version:'1.2.41'

1、String转JSONObject

前言：String 是JSONObject格式的字符串

eg:

JSONObject jSONObject = JSONObject.parseObject(String);

2、String转JSONArray

前言：String 是JSONArray格式的字符串

eg:

JSONArray jsonArray= JSONArray.parseArray(String);

3、JSONObject中的数组提取为JSONArray

eg:

{
  "AreaName": "北京",
  "CityId": 110100,
  "NoMarket": false,
  "OldCityId": 646,
  "Pinyin": "beijing",
  "ProvinceId": 110000,
  "Result": [
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "Stelvio 钜惠23.4万起",
      "Url": "//www.autohome.com.cn/market/201904/100223763.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "马驹桥林肯中心年中大促",
      "Url": "//www.autohome.com.cn/market/201906/100230932.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "星越平价销售13.58万元起",
      "Url": "//www.autohome.com.cn/dealer/201906/367011492.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "哈弗F5限时优惠8000元",
      "Url": "//www.autohome.com.cn/dealer/201906/366897778.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "购元新能源价格暂无优惠",
      "Url": "//www.autohome.com.cn/dealer/201906/366897034.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "瑞虎3xe冰点价促销中！",
      "Url": "//www.autohome.com.cn/dealer/201906/366889724.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "购奔奔EV现钜惠5.1万元",
      "Url": "//www.autohome.com.cn/dealer/201906/366843204.html"
    },
    {
      "ItemName": "优惠",
      "ItemUrl": "/list/a646c12-1.html",
      "Title": "购宝马7系价格暂无优惠",
      "Url": "//www.autohome.com.cn/dealer/201906/366588080.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "途观L价格直降7.6万元",
      "Url": "//www.autohome.com.cn/dealer/201906/366568937.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "购凯迪拉克XTS降8万",
      "Url": "//www.autohome.com.cn/dealer/201906/366500646.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "汉兰达可试驾购车无优惠",
      "Url": "//www.autohome.com.cn/dealer/201906/366384207.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "宝马M4价格稳定无优惠",
      "Url": "//www.autohome.com.cn/dealer/201906/366156789.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "奥迪A8促销直降26.33万元",
      "Url": "//www.autohome.com.cn/dealer/201906/366925378.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "英菲尼迪Q50L可降6.3万",
      "Url": "//www.autohome.com.cn/dealer/201906/366863516.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "帝豪新能源价格降8.25万",
      "Url": "//www.autohome.com.cn/dealer/201906/366877669.html"
    },
    {
      "ItemName": "预定",
      "ItemUrl": "/list/a646c14-1.html",
      "Title": "撼路者在售现钜惠5万",
      "Url": "//www.autohome.com.cn/dealer/201906/366912121.html"
    }
  ]
}

提取Result对应的数组

JSONArray jsonArray= jsonObject.getJSONArray("Result");

4、JSONArray提取为JSONObject

eg:

JSONObject jsonObject = jsonArray.getJSONObject(0);

5、JSONObject获取value

1、object.getString("key")

2、object.get("key")

6、获取JSONObject的ket value

JSONArray dateArr = new JSONArray();
    Set<String> key = dateArr .keySet();
    for (String keyObj:key) {
      JSONArray hisData = history.getJSONArray(keyObj);      
    }

7、遍历JSONArray

第一种for循环
        JSONArray seriesArr = new JSONArray();
        for(int i=0;i<seriesArr .size();i++){
          JSONObject object = eggsArr.getJSONObject(i);
        }


第二种for增强
        JSONArray pzListArr = new JSONArray();
        for (Object obj:pzListArr) {
          JSONObject dataObj = JSONObject.parseObject(obj.toString());
        }

8、

Map<String, Object> paraMap = new HashMap<String, Object>();

JSONObject.toJSONString(paraMap)

自动过滤参数为null的数值

8、javaBean转为JSONObject

未完待续······

9、List<实体类>转String

import com.alibaba.fastjson.JSONObject;


List<实体类> value1 = 。。。。。。
JSONObject.toJSONString(value1 )10、JSONArray转List<实体类>

看你开心用哪个，object和array的区别没有细究

10、JSONArray转List<实体类>

import com.alibaba.fastjson.JSONArray;
JSONArray objects = JSONArray.parseArray(categoryConstantInfoFromRedis);
List<实体类> categoryConstantInfos = objects.toJavaList(实体类名.class);
众里寻他千百度！！！toJavaList

找不到方法的时候，去看看JSONArray，JSONObject的源码，很多都有封装好的，你不会失望的

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