如何解析json字符串及返回json数据到前端

JSON 语法是 JavaScript 对象表示法语法的子集。
 - 数据在名称/值对中：如 "firstName" : "John"
 -数据由逗号分隔
 -花括号保存对象
 - 方括号保存数组

而组成JSON的值可以为以下几种：

-数字（整数或浮点数）
-字符串（在双引号中）
- 逻辑值（true 或 false）
-数组（在方括号中）
-对象（在花括号中）
- null

        <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.2</version>
        </dependency>

[
  {
    "zone_id": 100001,
    "title": "围栏1",
    "zone_geometry": {
      "type": "polygon",
      "apex": [
        {
          "lng": "113.166096",
          "lat": "31.727309"
        },      
        {
          "lng": "113.222498",
          "lat": "31.689881"
        }     
      ]
    }
  },
  {
    "zone_id": 100002,
    "title": "围栏2",
    "zone_geometry": {
      "type": "polygon",
      "apex": [
        {
          "lng": "113.462342",
          "lat": "31.626034"
        },
        {
          "lng": "113.472525",
          "lat": "31.538983"
        }
      ]
    }
  },
]

public classHerdCamera {
    privateString zone_id;
    privateString title;
    privateZoneGeometry zoneGeometry;
    publicString getZone_id() {
        returnzone_id;
    }
    public voidsetZone_id(String zone_id) {
        this.zone_id =zone_id;
    }
    publicString getTitle() {
        returntitle;
    }
    public voidsetTitle(String title) {
        this.title =title;
    }
    publicZoneGeometry getZoneGeometry() {
        returnzoneGeometry;
    }
    public voidsetZoneGeometry(ZoneGeometry zoneGeometry) {
        this.zoneGeometry =zoneGeometry;
    }
}

importjava.util.List;
public classZoneGeometry {
    privateString type;
    private List<Locations>apex;
    publicString getType() {
        returntype;
    }
    public voidsetType(String type) {
        this.type =type;
    }
    public List<Locations>getApex() {
        returnapex;
    }
    public void setApex(List<Locations>apex) {
        this.apex =apex;
    }
}

public classApex {
    private doublelng;
    private doublelat;
    public Apex(double lng, doublelat) {
        super();
        this.lng =lng;
        this.lat =lat;
    }
    public doublegetLng() {
        returnlng;
    }
    public void setLng(doublelng) {
        this.lng =lng;
    }
    public doublegetLat() {
        returnlat;
    }
    public void setLat(doublelat) {
        this.lat =lat;
    }
}

public Map<String,Object> herdcameradata() throwsException{
        String fileName = "fileName";
　　　　 JsonParser parser = new JsonParser(); //创建JSON解析器
        JsonArray array = (JsonArray) parser.parse(new FileReader(fileName));    //首先解析出来的是JsonArray

        Map< String, Object> result=new HashMap<>();
        List<Object> herdCameras = new ArrayList<Object>();
        for (int i = 0; i < array.size(); i++) {
            JsonObject subObject = array.get(i).getAsJsonObject();　　　　　　　 　//第二步获得的是JsonObject
            HerdCamera herd = newHerdCamera();
            herd.setZone_id(subObject.get("zone_id").getAsString());　　　　　　　//然后依次获取subObject中的每一个字段
            herd.setTitle(subObject.get("title").getAsString());
            ZoneGeometry zoneGeometry = newZoneGeometry();
            JsonObject subObject2 = subObject.getAsJsonObject("zone_geometry");　　//第四步又获得一个zone_geometry的JsonObject
            zoneGeometry.setType(subObject2.get("type").getAsString());　　　　　　　//然后获取zone_geometry内部的type对象
            JsonArray array2 = subObject2.getAsJsonArray("apex");　　　　　　　　　　　//第五步中apex是一个jsonArray
            List<Locations> locationList = new ArrayList<Locations>();
            for (int j = 0; j < array2.size(); j++) {
                Locations location = newLocations();
                JsonObject subObject3 =array2.get(j).getAsJsonObject();
                location.setLng(subObject3.get("lng").getAsString());
                location.setLat(subObject3.get("lat").getAsString());
                locationList.add(location);
            }
            zoneGeometry.setApex(locationList);
            herd.setZoneGeometry(zoneGeometry);
            herdCameras.add(herd);
        }
        result.put("cameras",herdCameras );
        returnresult;
    }