具有动态值的 JSON 字符串到对象映射

Question

我正在使用第三方jsonString，我正在尝试解析json，但有时JSON对象"RadarReports"是一个列表，有时是对象。

{"RadarReports": {
"executionTime": "135",
"RadarReport": {
"abc": "1116591",
"name": "abc",
"id": "2019050311582056119",
"ownerId": "xyz"
},
"size" :"1"
}}

====

=============

{"RadarReports": {
"executionTime": "113",
"RadarReport": [
{
"abc": "1116591",
"name": "abc",
"id": "2019050311582056119",
"ownerId": "xyz"
},
{
"abc": "1116591",
"name": "abc",
"id": "2019050311582056119",
"ownerId": "xyz"
},
]
"size" : "2"
}}

我在下面尝试解析，但当单个对象进入图片时失败，需要接受单个对象和对象列表。

@Data
public class Radarreports {
private int size;
private ArrayList<RadarreportSet> RadarReportSet;
private ArrayList<RadarReport> RadarReport;
}
@Data
public
class ReportsResponse {
Radarreports RadarReports;
}
URL url = new URL(queryUrl);
BufferedReader br = new BufferedReader(new InputStreamReader(url.openStream()));
Gson gson = new GsonBuilder().create();
ReportsResponse radarReports = gson.fromJson(br, ReportsResponse.class);

Answer 1

您可以使用自定义TypeAdapterFactory来解决此问题，该创建一个适配器，该适配器首先查看 JSON 数据的类型，然后在 JSON 对象未包装在 JSON 数组中的情况下添加特殊处理：

// Only intended for usage with @JsonAdapter
class SingleObjectOrListAdapterFactory implements TypeAdapterFactory {
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
// Note: Cannot use getDelegateAdapter due to https://github.com/google/gson/issues/1028
TypeAdapter<T> listAdapterDelegate = gson.getAdapter(type);
TypeAdapter<JsonObject> jsonObjectAdapter = gson.getAdapter(JsonObject.class);
return new TypeAdapter<T>() {
@Override
public void write(JsonWriter out, T value) throws IOException {
listAdapterDelegate.write(out, value);
}
@Override
public T read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.BEGIN_OBJECT) {
// Wrap JSON object in a new JSON array before parsing it
JsonObject jsonObject = jsonObjectAdapter.read(in);
JsonArray jsonArray = new JsonArray();
jsonArray.add(jsonObject);
return listAdapterDelegate.fromJsonTree(jsonArray);
} else {
return listAdapterDelegate.read(in);
}
}
};
}
}

然后可以使用@JsonAdapter为受影响的字段指定工厂：

@JsonAdapter(SingleObjectOrListAdapterFactory.class)
private ArrayList<RadarReport> RadarReport;