我正在尝试解析一个如下所示的 Json 数组:
{
"FoodItemData": [
{
"country": "GB",
"id": "100",
"name": "Steak and Kidney Pie",
"description": "Tender cubes of steak, with tender lamb kidney is succulent rich gravy. Served with a side of mashed potatoes and peas.",
"category": "Dinner",
"price": "15.95"
},
{
"country": "GB",
"id": "101",
"name": "Toad in the Hole",
"description": "Plump British Pork sausages backed in a light batter. Served with mixed vegetables and a brown onion gravy.",
"category": "Dinner",
"price": "13.95"
},
{
"country": "GB",
"id": "102",
"name": "Ploughman’s Salad",
"description": "Pork Pie, Pickled Onions, Pickled relish Stilton and Cheddar cheeses and crusty French bread.",
"category": "Lunch",
"price": "10.95"
}
]
}
我正在使用 Gson
来解析这个 Json。
URL url = getClass().getClassLoader().getResource("FoodItemData.json");
FileReader fileReader = null;
try {
fileReader = new FileReader(url.getPath());
} catch (FileNotFoundException e) {
e.printStackTrace();
}
JsonReader jsonReader = new JsonReader(fileReader);
Gson gson = new Gson();
JsonParser parser = new JsonParser();
JsonArray Jarray = parser.parse(jsonReader).getAsJsonArray();
List<FoodItem> listOfFoodItems = new ArrayList<FoodItem>();
for (JsonElement obj : Jarray) {
FoodItem foodItem = gson.fromJson(obj, FoodItem.class);
listOfFoodItems.add(foodItem);
}
此代码导致 java.lang.IllegalStateException: This is not a JSON Array
异常。 FoodItem
类包含与 Json 中同名的变量。
public class FoodItem {
private String id;
private String name;
private String description;
private String category;
private String price;
private String country;
}
我在这里遗漏了什么吗?我尝试使用 this answer 中给出的以下代码,但我得到了与该问题中提到的相同的异常。任何帮助将不胜感激。
Gson gson = new GsonBuilder().create();
Type collectionType = new TypeToken<List<FoodItem>>(){}.getType();
List<FoodItem> foodItems = gson.fromJson(jsonReader, collectionType);
最佳答案
你需要改变这个
JsonArray jarray = parser.parse(jsonReader).getAsJsonArray();
到
JsonArray jarray = (JsonArray) parser.parse(jsonReader).getAsJsonObject().get("FoodItemData");
您的 JSON 在根目录中包含一个名为 FoodItemData
的 JSON 对象.该元素包含您尝试映射到 List<FoodItem>
的 JSON 数组
或者,您可以创建一个类,其中包含一个名为 FoodItemData
的字段那是一个List<FoodItem>
public class RootElement {
List<FoodItem> FoodItemData;
// the good stuff
}
然后像这样解析
RootElement root = gson.fromJson(jsonReader, RootElement.class);
System.out.println(root.FoodItemData);
另请注意,Java 约定规定变量名应以小写字符开头。
关于java - 解析 Json 数组导致 This is not a JSON Array 异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19780576/