java - 使用 jackson 从 json 数组中检索值

Question

我正在编写代码，需要从 json 数组中获取特定的值。我的 json 如下:

{
  "coord": {
    "lon": 68.37,
    "lat": 25.39
  },
  "weather": [{
    "id": 800,
    "main": "Clear",
    "description": "clear sky",
    "icon": "01d"
  }],
  "base": "stations",
  "main": {
    "temp": 302.645,
    "pressure": 1023.33,
    "humidity": 48,
    "temp_min": 302.645,
    "temp_max": 302.645,
    "sea_level": 1025.53,
    "grnd_level": 1023.33
  },
  "wind": {
    "speed": 1.81,
    "deg": 54.0002
  },
  "clouds": {
    "all": 0
  },
  "dt": 1479887201,
  "sys": {
    "message": 0.0023,
    "country": "PK",
    "sunrise": 1479865789,
    "sunset": 1479904567
  },
  "id": 1176734,
  "name": "Hyderabad",
  "cod": 200
}

我想从天气 数组中获取id。如果有很多，我想获取第一个项目的 ID。

请让我知道我该怎么做。

我用来获取天气数组的代码是:

text = builder.toString();
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(text, new TypeReference<Map<String, Object>>() {
});

List mainMap2 = (List) map.get("weather");
for (Object item : mainMap2) {
    System.out.println("itemResult" + item.toString());
}

这里，text 是 json 字符串。

Answer 1

下一行应该可以解决问题

int id = (int)((Map)mainMap2.get(0)).get("id");

您的代码可以修改如下:

text = builder.toString();
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(text, new TypeReference<Map<String, Object>>() {
});

List mainMap2 = (List) map.get("weather");
//for (Object item : mainMap2) {
//    System.out.println("itemResult" + item.toString());
//}
int id = (int)((Map)mainMap2.get(0)).get("id");
System.out.println(id);