[英]How does Polymorphism work with Gson (Retrofit)
這是我的Retrofit
實例:
@Provides
@Singleton
ApiManager provideApiManager() {
RxJava2CallAdapterFactory rxAdapter = RxJava2CallAdapterFactory.create();
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.addNetworkInterceptor(new StethoInterceptor())
.build();
Gson gson = new GsonBuilder().create();
GsonConverterFactory converterFactory = GsonConverterFactory.create(gson);
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(AppConstants.BASE_URL)
.addConverterFactory(converterFactory)
.addCallAdapterFactory(rxAdapter)
.client(okHttpClient)
.build();
return retrofit.create(ApiManager.class);
}
模型:
class AbstractMessage {
String id;
}
class TextMessage extends AbstractMessage {
String textMessage;
}
class ImageMessage extends AbstractMessage {
String url;
String text;
}
請求:
@GET("direct/messages")
Observable<List<AbstractMessage>> getMessages(@Header("Authorization") String authHeader, @Body RequestObject request);
執行請求:
apiManager.getMessages(authHeader, requestObject)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<List<AbstractMessage>>() {
@Override
public void accept(List<AbstractMessage> messages) throws Exception {
...
}
});
當我執行一個請求時,我收到了一個AbstractMessage
對象的集合。 JSON
可以包含文本和圖像消息。 在我的例子中, JSON
轉換器創建AbstractMessage
並僅映射id
字段。 如何使轉換器創建TextMessage
和ImageMessage
對象映射所有匹配的字段,然后將其ImageMessage
轉換為AbstractMessage
。 或者可能還有其他一些解決方案。
您必須為對象AbstractMessage,TextMessage和ImageMessage創建RuntimeTypeAdapterFactory ,然后必須將其設置為gson實例。
假設你有這些對象:
public class Animal {
protected String name;
protected String type;
public Animal(String name, String type) {
this.name = name;
this.type = type;
}
}
public class Dog extends Animal {
private boolean playsCatch;
public Dog(String name, boolean playsCatch) {
super(name, "dog");
this.playsCatch = playsCatch;
}
}
public class Cat extends Animal {
private boolean chasesLaser;
public Cat(String name, boolean chasesLaser) {
super(name, "cat");
this.chasesLaser = chasesLaser;
}
}
下面是您需要的RuntimeTypeAdapter ,以便正確地反序列化(和序列化)這些對象:
RuntimeTypeAdapterFactory<Animal> runtimeTypeAdapterFactory = RuntimeTypeAdapterFactory
.of(Animal.class, "type")
.registerSubtype(Dog.class, "dog")
.registerSubtype(Cat.class, "cat");
Gson gson = new GsonBuilder()
.registerTypeAdapterFactory(runtimeTypeAdapterFactory)
.create();
RunsonTypeAdapterFactory.java類不隨Gson包一起提供,因此您必須手動下載它。
請注意,你的問題的標題應該是“與Gson的多態性”
我希望它有所幫助。
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