Question

我有一个嵌套的JSON对象，比如

{
  "hours": {
    "Friday": {
      "close": "21:00",
      "open": "11:00"
    },
    "Tuesday": {
      "close": "21:00",
      "open": "11:00"
    }
  },
  "open": true,
  "categories": [
    "Fast Food",
    "Restaurants"
  ],
  "city": "Dravosburg",
  "review_count": 7,
  "name": "Mr Hoagie",
  "neighborhoods": [

  ],
  "longitude": -79.9007057,
  "state": "PA",
  "stars": 3.5,
  "latitude": 40.3543266,
  "attributes": {
    "Take-out": true,
    "Drive-Thru": false,
    "Good For": {
      "dessert": false,
      "latenight": false
    },
    "Caters": false,
    "Noise Level": "average",
    "Takes Reservations": false,
    "Delivery": false,
    "Ambience": {
      "romantic": false,
      "intimate": false,
      "classy": false
    },
    "Parking": {
      "garage": false,
      "street": false
    },
    "Has TV": false,
    "Outdoor Seating": false,
    "Attire": "casual"
  },
  "type": "business"
}

我正在使用GSON来解析这个json对象。我创建了POJO类，如下所示：

 public class BusinessPojo {

   private String type;
   private String name;
   private ArrayList<String> neighborhoods = new ArrayList<>();
   private ArrayList<String> categories = new ArrayList<>();
   private BusinessDay hours = new BusinessDay();
   private String city;
   private boolean open;
   private String state;
   private double latitude;
   private double longitude;
   private float stars;
   private int review_count;
   private BusinessAttributes attributes;
//getters and setters
}
public class BusinessDay {
    private BusinessHourTime monday = new BusinessHourTime();
    private BusinessHourTime tueday = new BusinessHourTime();
    private BusinessHourTime wednesday = new BusinessHourTime();
    private BusinessHourTime thursday = new BusinessHourTime();
    private BusinessHourTime friday = new BusinessHourTime();
    private BusinessHourTime satday = new BusinessHourTime();
    private BusinessHourTime sunday = new BusinessHourTime();
// getters and setters
}
public class BusinessHourTime {
    private String open;
    private String close;
//getters and setters
}

，Attributes类似，Parking，Ambience和GoodFor的属性内部。这是我的代码：

String line = "json object"
Gson g = new Gson();
BusinessPojo businessJsonObj = g.fromJson(line, BusinessPojo.class);

当我尝试访问"Drive-Thru"时

System.out.println(businessJsonObj.getAttributes().isDriveThru());

我获得了价值false，但是当我尝试从open或Friday访问Tuesday时，我得到了null

System.out.println(businessJsonObj.getHours().getTuesday().getOpen());

有人能帮我理解我在代码中犯了什么错误吗？

Answer 1

从风格的角度来看，给定的JSON存在一些问题。这应该考虑用于GSON映射。默认情况下，GSON将DTO类字段名称“对称地”映射到JSON字段名称（将忽略getter和setter）：如果您的最顶层类字段名为foo，则给定的JSON应包含最顶层字段也称为foo，以便使用默认规则进行映射。

但是，GSON具有@SerializedName注释的名称覆盖机制。在你的情况下，它应该是：

public static final class BusinessDay {
    ...
    @SerializedName("Tuesday")
    private BusinessHourTime tueday = new BusinessHourTime();
    ...

用例（假设为了简单起见，可以直接访问字段的静态嵌套类）：

System.out.println(businessJsonObj.hours.tueday.open);

11:00

同样地，我假设，isDriveThru()永远无法为true工作，无论JSON如何，总是返回false，因为名称Drive-Thru以资本开头字母（如果您的映射类字段也以D开头，并且其名称中包含连字符-并不重要）。由于后者在Java中不允许使用带连字符的命名问题，因此您必须明确地映射该字段：

@SerializedName("Drive-Thru")
private boolean isDriveThru;

另外，如果可能的话，我强烈建议修复JSON属性名称以摆脱非标准命名：仅仅是用于JSON属性名称的camelCase，如Friday - ＆gt; friday，review_count - ＆gt; reviewCount，Take-out - ＆gt; takeOut，Good For - ＆gt; goodFor，等等。修改格式后，大多数情况下您都不需要@SerializedName注释（还要注意tueday的{{1}}，tuesday的{{1}}等拼写错误，等等）。如果不可能，只需使用此注释来修复映射，如上所述。

使用GSON进行嵌套的JSON对象解析

1 个答案: