入参数据示例：

{
    "respCode": "0000",
    "respMsg": "请求成功",
    "bizSeqNo": "22022120001184432418054888526616",
    "transTime": "20220221180548",
    "success": true,
    "tokenArr": [
        {
            "value": "xxxx",
            "expire_in": 96,
            "expire_time": "20220221180724"
        }
    ]
}

取出其中的value值

String req = "这里是入参";
//1.先转换成map
Map map = JSON.parseObject(req, Map.class);
//2.取出数组
JSONArray tokenArr = (JSONArray) map.get("tokenArr");
//3.把数组的第一个转换成map
HashMap tokenArrMap = JSON.parseObject(
				tokenArr.getString(0), HashMap.class);
//4.取出value
String value = (String) tokenArrMap.get("value");

java中获取json中的数组转化为List

//循环取到records的数值
 for (int i = 0; i < records.size(); i++) {
                Device item = JSONObject.parseObject(JSONObject.toJSONString(records.get(i)), Device.class);
                //取到设备id
                String id = item.getId();
                //该字段是json数组这样获取
                JSONArray alarmThreshold = JSONArray.parseArray(item.getAlarmThreshold());
                //判空处理
                if (alarmThreshold != null && alarmThreshold.size() > 0) {
                //该字段为多个json数组虚幻取出单个
                    for (int h = 0; h < alarmThreshold.size(); h++) {
                    //获取到该字段全部数值
                        String alarmThresholds = String.valueOf(JSONObject.parseObject(alarmThreshold.getString(h)).get("data"));
                        //此处存入到list中
                        List<AlarmThresholdData> alarmThresholdData = JSONObject.parseObject(alarmThresholds, ArrayList.class);
                        //alarmThresholdData 此处改字段已经是单个data，循环遍历该单个data
                        for (int a = 0; a < alarmThresholdData.size(); a++) {
                            AlarmThresholdData items = JSONObject.parseObject(JSONObject.toJSONString(alarmThresholdData.get(a)), AlarmThresholdData.class);
                            //取出该json字段中具体属性值
                            String alarmLvId = items.getAlarmLvId();
                            String value = items.getValue();
                            String conditional = items.getConditional();

重要方法转：
获取到的json字段数据库为json数组

JSONArray alarmThreshold = JSONArray.parseArray(item.getAlarmThreshold());

对该数组进行判空处理，继续循环遍历。取出json数组单个json数据。存入到list中

 if (alarmThreshold != null && alarmThreshold.size() > 0) {
                    for (int h = 0; h < alarmThreshold.size(); h++) {
                        String alarmThresholds = String.valueOf(JSONObject.parseObject(alarmThreshold.getString(h)).get("data"));
                        List<AlarmThresholdData> alarmThresholdData = JSONObject.parseObject(alarmThresholds, ArrayList.class);

循环遍历该List取出Json数组里面具体的单个字段值

  for (int a = 0; a < alarmThresholdData.size(); a++) {
                            AlarmThresholdData items = JSONObject.parseObject(JSONObject.toJSONString(alarmThresholdData.get(a)), AlarmThresholdData.class);
                            String alarmLvId = items.getAlarmLvId();
                            String value = items.getValue();
                            String conditional = items.getConditional();