java - 如何使用 JSON 处理困难对象

Question

我对动态 JSON 数据有疑问。我不知道如何将它放入我的JAVA类中。我需要“路线”数据。但我不知道我应该如何处理这个“”2019-05-27”:{...”。

它是 JSON 文件的一部分...

{
  "2019-05-26": {
    "lastUpdate": "2019-05-26 06:05:02",
    "routes": [
      {
        "routeId": 107,
        "agencyId": 18
      },
      {
        "routeId": 222,
        "agencyId": 22
      }
    ]
  },
  "2019-05-27": {
    "lastUpdate": "2019-05-27 06:05:02",
    "routes": [
      {
        "routeId": 33,
        "agencyId": 14
      },
      {
        "routeId": 345,
        "agencyId": 2232
      }
    ]
  }
}

下面的代码不起作用。它不是Map<String,Map<String, String>> 。我认为是-

Gson gson = new Gson();

    Type mapType = new TypeToken<Map<String,Map<String, String>>>() {}.getType();
    Map<String,Map<String, String>> map = null;
    try {
        map = gson.fromJson(new FileReader("routes.json"), mapType);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

我应该怎么做才能获取这些数据？

Answer 1

创建这样的 POJO 类:

public class MyObject {
    private List<Route> routes;
    private String lastUpdate;

    public MyObject(List<Route> routes, String lastUpdate) {
        this.routes = routes;
        this.lastUpdate = lastUpdate;
    }

    // assume getters and setters
}

public class Route {
    private String routeId;
    private String agencyId;

    public Route(String routeId, String agencyId) {
        this.routeId = routeId;
        this.agencyId = agencyId;
    }
    // assume getters and setters
}

测试它:

public static void main(String[] args) throws IOException {
        Gson gson = new Gson();

        String json = Files.lines(Paths.get("src/main/resources/data.json")).collect(Collectors.joining());

        Type mapType = new TypeToken<Map<String, MyObject>>() {}.getType();
        Map<String, MyObject> map = gson.fromJson(json, mapType);

        map.forEach((s, myObject) -> System.out.println(s + " " + myObject.getLastUpdate()));

}

输出是:

2019-05-26 2019-05-26 06:05:02
2019-05-27 2019-05-27 06:05:02

您只需创建一个以日期为键、以自定义对象为值的 map 。