Gson 라이브러리를 사용하여 JSON 문자열을 어떻게 변환합니까?

Gson 라이브러리를 사용하여 JSON 문자열을 어떻게 변환합니까?

Gson 라이브러리를 사용하여 JSON 문자열을 어떻게 변환합니까?

ArrayList

커스텀 클래스의

JsonLog

기본적으로는

JsonLog

SMS 로그, 통화 로그, 데이터 로그 등 Android 앱에 의해 작성된 다양한 종류의 로그에 의해 구현되는 인터페이스입니다.

ArrayList

모든 것을 모은 것입니다.6번째 줄에 오류가 계속 나요.

public static void log(File destination, JsonLog log) {
    Collection<JsonLog> logs = null;
    if (destination.exists()) {
        Gson gson = new Gson();
        BufferedReader br = new BufferedReader(new FileReader(destination));
        logs = gson.fromJson(br, ArrayList<JsonLog>.class); // line 6
        // logs.add(log);
        // serialize "logs" again
    }
}

컴파일러는 제가 타입을 참조하고 있다는 것을 이해하지 못하는 것 같습니다.

ArrayList

.내가 어떻게 해야 하나요?

You may use TypeToken to load the json string into a custom object.

logs = gson.fromJson(br, new TypeToken<List<JsonLog>>(){}.getType());

Documentation:

Represents a generic type T.

Java doesn't yet provide a way to represent generic types, so this class does. Forces clients to create a subclass of this class which enables retrieval the type information even at runtime.

예를 들어 다음과 같은 유형의 리터럴을 작성하려면

List<String>

빈 어나니머스 내부 클래스를 만들 수 있습니다.

TypeToken<List<String>> list = new TypeToken<List<String>>() {};

이 구문을 사용하여 다음과 같은 와일드카드 매개 변수가 있는 유형 리터럴을 만들 수 없습니다.

Class<?>

또는

List<? extends CharSequence>

.

Kotlin:

If you need to do it in Kotlin you can do it like this:

val myType = object : TypeToken<List<JsonLong>>() {}.type
val logs = gson.fromJson<List<JsonLong>>(br, myType)

Or you can see this answer for various alternatives.

Your JSON sample is:

{
    "status": "ok",
    "comment": "",
    "result": {
    "id": 276,
    "firstName": "mohamed",
    "lastName": "hussien",
    "players": [
            "player 1",
            "player 2",
            "player 3",
            "player 4",
            "player 5"
    ]
}

so if you want to save arraylist of modules in your SharedPrefrences so :

1- will convert your returned arraylist for json format using this method

public static String toJson(Object jsonObject) {
    return new Gson().toJson(jsonObject);
}

2- Save it in shared prefreneces

PreferencesUtils.getInstance(context).setString("players", toJson((.....ArrayList you want to convert.....)));

3- to retrieve it at any time get JsonString from Shared preferences like that

String playersString= PreferencesUtils.getInstance(this).getString("players");

4- convert it again to array list

public static Object fromJson(String jsonString, Type type) {
    return new Gson().fromJson(jsonString, type);
}

ArrayList<String> playersList= (ArrayList<String>) fromJson(playersString,
                    new TypeToken<ArrayList<String>>() {
                    }.getType());

this solution also doable if you want to parse ArrayList of Objects Hope it's help you by using Gson Library .

Kotlin

data class Player(val name : String, val surname: String)

val json = [
  {
    "name": "name 1",
    "surname": "surname 1"
  },
  {
    "name": "name 2",
    "surname": "surname 2"
  },
  {
    "name": "name 3",
    "surname": "surname 3"
  }
]

val typeToken = object : TypeToken<List<Player>>() {}.type
val playerArray = Gson().fromJson<List<Player>>(json, typeToken)

OR

val playerArray = Gson().fromJson(json, Array<Player>::class.java)

Why nobody wrote this simple way of converting JSON string in List ?

List<Object> list = Arrays.asList(new GsonBuilder().create().fromJson(jsonString, Object[].class));

If you want to use Arrays, it's pretty simple.

logs = gson.fromJson(br, JsonLog[].class); // line 6

를 제공하다

JsonLog

배열로서

JsonLog[].class

If you want convert from Json to a typed ArrayList , it's wrong to specify the type of the object contained in the list. The correct syntax is as follows:

 Gson gson = new Gson(); 
 List<MyClass> myList = gson.fromJson(inputString, ArrayList.class);

I am not sure about gson but this is how you do it with Jon.sample hope there must be similar way using gson

{ "Players": [ "player 1", "player 2", "player 3", "player 4", "player 5" ] }

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

import java.io.FileReader;
import java.util.List;

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

public class JosnFileDemo {

    public static void main(String[] args) throws Exception
    {
        String jsonfile ="fileloaction/fileName.json";


                FileReader reader = null;
                JSONObject jsb = null;
                try {
                    reader = new FileReader(jsonfile);
                    JSONParser jsonParser = new JSONParser();
                     jsb = (JSONObject) jsonParser.parse(reader);
                } catch (Exception e) {
                    throw new Exception(e);
                } finally {
                    if (reader != null)
                        reader.close();
                }
                List<String> Players=(List<String>) jsb.get("Players");
                for (String player : Players) {
                    System.out.println(player);
                }           
    }
}

You have a string like this.

"[{"id":2550,"cityName":"Langkawi","hotelName":"favehotel Cenang Beach - Langkawi","hotelId":"H1266070"},
{"id":2551,"cityName":"Kuala Lumpur","hotelName":"Metro Hotel Bukit Bintang","hotelId":"H835758"}]"

Then you can covert it to ArrayList via Gson like

var hotels = Gson().fromJson(historyItem.hotels, Array<HotelInfo>::class.java).toList()

HotelInfo 클래스는 다음과 같습니다.

import com.squareup.moshi.Json

data class HotelInfo(

    @Json(name="cityName")
    val cityName: String? = null,

    @Json(name="id")
    val id: Int? = null,

    @Json(name="hotelId")
    val hotelId: String? = null,

    @Json(name="hotelName")
    val hotelName: String? = null
)

인코틀린 송신용 : Arraylist를 송신하는 경우

Gson().toJson(arraylist)

수신용:Array List를 수신한 경우

var arraylist = Gson().fromJson(argument, object : TypeToken<ArrayList<LatLng>>() {}.type)  

송신용 : ModelClass (예: LatLgModel.class)를 송신하는 경우

var latlngmodel = LatlngModel()
latlngmodel.lat = 32.0154
latlngmodel.lng = 70.1254

Gson().toJson(latlngModel)

수신용:Model Class를 받는 경우

var arraylist = Gson().fromJson(argument,LatLngModel::class.java )  

언급URL : https://stackoverflow.com/questions/12384064/gson-convert-from-json-to-a-typed-arraylistt