英文:
how to De-serialize a List<Generic<Enum>> using Gson library
问题
我需要将这个 Json 字符串反序列化为一个 POJO（普通 Java 对象）。
Json:
[
{
"first": {
"value": 12,
"suit": {
"name": "heart"
}
},
"second": {
"value": 12,
"suit": {
"name": "spade"
}
}
},
{
"first": {
"value": 8,
"suit": {
"name": "club"
}
},
"second": {
"value": 9,
"suit": {
"name": "club"
}
}
}
]
我正在尝试将这个 json 字符串反序列化为一个 `ArrayList<Pair<Card>>`，其中 `Pair<?>` 类是泛型，而 `Card` 类是一个枚举。
我尝试使用以下方法进行：
Type listType = new TypeToken<ArrayList<Pair<Card>>>(){}.getType();
List<Pair<Card>> handList = gson.fromJson(hands, listType);
Card 类：
```java
public enum Card {
@SerializedName("value")
public int value;
@SerializedName("suit")
public Suit suit;
Card(int value, Suit suit) {
this.value = value;
this.suit = suit;
}
}
Suit 类：
public enum Suit {
@SerializedName("name")
public String name;
Suit(String name) {
this.name = name;
}
}
然而 Gson 一直抛出 IllegalStateException 异常：
java.lang.IllegalStateException: Expected a string but was BEGIN_OBJECT at line 3 column 15 path $[0].first
英文:
I need to De-serialize this Json string into a POJO.
Json:
[
{
"first" : {
"value" : 12,
"suit" : {
"name" : "heart"
}
},
"second" : {
"value" : 12,
"suit" : {
"name" : "spade"
}
}
},
{
"first" : {
"value" : 8,
"suit" : {
"name" : "club"
}
},
"second" : {
"value" : 9,
"suit" : {
"name" : "club"
}
}
}
]
I am trying to de-serialize this json string to a ArrayList<Pair<Card>> where the Pair<?> class is generic and the Card class is an enum.
I am attempting to do this via the following:
Type listType = new TypeToken<ArrayList<Pair<Card>>>(){}.getType();
List<Pair<Card>> handList = gson.fromJson(hands, listType);
Card class:
public enum Card {
@SerializedName("value")
public int value;
@SerializedName("suit")
public Suit suit;
Card(int value, Suit suit) {
this.value = value;
this.suit = suit;
}
Suit class:
public enum Suit {
@SerializedName("name")
public String name;
Suit(String name) {
this.name = name;
}
}
However Gson keeps throwing IllegalStateException's
java.lang.IllegalStateException: Expected a string but was BEGIN_OBJECT at line 3 column 15 path $[0].first
答案1
得分: 0
你可以为 Card 类创建一个自定义的反序列化器（Deserializer）：
public class CardDeserializer implements JsonDeserializer<Card> {
@Override
public Card deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
JsonObject obj = json.getAsJsonObject();
JsonObject jobject = obj.getAsJsonObject("suit");
// 在这里使用这些值创建 Card 对象
// obj.get("value").getAsString();
// jobject.get("name").getAsString();
// ...
return card;
}
}
然后在使用之前在 Gson 构建器中注册该反序列化器：
gson.registerTypeAdapter(Card.class, new CardDeserializer());
英文:
You can create a custom Deserializer for Card class
public class CardDeserializer implements JsonDeserializer<Card> {
@Override
public Card deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
JsonObject obj = json.getAsJsonObject();
JsonObject jobject = obj.getAsJsonObject("suit");
//Create Card here using those value
//obj.get("value").getAsString();
//jobject.get("name").getAsString();
...
return card;
}
}
And register in gson builder before work
gson.registerTypeAdapter(Card.class, new CardDeserializer());
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