根据我的研究以及使用gson-2.0时，你确实不想使用registerTypeHierarchyAdapter方法，而是更平凡的registerTypeAdapter。而且，你当然不需要为派生类做instanceofs或编写适配器：只为基类或接口提供一个适配器，当然，你对派生类的默认序列化感到满意。无论如何，这是代码（删除了打包和导入）（也可以在github中找到）：
基类（在我的情况下为接口）：
public interface IAnimal { public String sound(); }
这两个派生类Cat：
public class Cat implements IAnimal {
public String name;
public Cat(String name) {
super();
this.name = name;
}
@Override
public String sound() {
return name + " : \"meaow\"";
};
}
And Dog:
public class Dog implements IAnimal {
public String name;
public int ferocity;
public Dog(String name, int ferocity) {
super();
this.name = name;
this.ferocity = ferocity;
}
@Override
public String sound() {
return name + " : \"bark\" (ferocity level:" + ferocity + ")";
}
}
IAnimalAdapter：
public class IAnimalAdapter implements JsonSerializer<IAnimal>, JsonDeserializer<IAnimal>{
private static final String CLASSNAME = "CLASSNAME";
private static final String INSTANCE = "INSTANCE";
@Override
public JsonElement serialize(IAnimal src, Type typeOfSrc,
JsonSerializationContext context) {
JsonObject retValue = new JsonObject();
String className = src.getClass().getName();
retValue.addProperty(CLASSNAME, className);
JsonElement elem = context.serialize(src);
retValue.add(INSTANCE, elem);
return retValue;
}
@Override
public IAnimal deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
JsonObject jsonObject = json.getAsJsonObject();
JsonPrimitive prim = (JsonPrimitive) jsonObject.get(CLASSNAME);
String className = prim.getAsString();
Class<?> klass = null;
try {
klass = Class.forName(className);
} catch (ClassNotFoundException e) {
e.printStackTrace();
throw new JsonParseException(e.getMessage());
}
return context.deserialize(jsonObject.get(INSTANCE), klass);
}
}
和测试类：
public class Test {
public static void main(String[] args) {
IAnimal animals[] = new IAnimal[]{new Cat("Kitty"), new Dog("Brutus", 5)};
Gson gsonExt = null;
{
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(IAnimal.class, new IAnimalAdapter());
gsonExt = builder.create();
}
for (IAnimal animal : animals) {
String animalJson = gsonExt.toJson(animal, IAnimal.class);
System.out.println("serialized with the custom serializer:" + animalJson);
IAnimal animal2 = gsonExt.fromJson(animalJson, IAnimal.class);
System.out.println(animal2.sound());
}
}
}
当运行Test :: main时，将得到以下输出：
serialized with the custom serializer:
{"CLASSNAME":"com.synelixis.caches.viz.json.playground.plainAdapter.Cat","INSTANCE":{"name":"Kitty"}}
Kitty : "meaow"
serialized with the custom serializer:
{"CLASSNAME":"com.synelixis.caches.viz.json.playground.plainAdapter.Dog","INSTANCE":{"name":"Brutus","ferocity":5}}
Brutus : "bark" (ferocity level:5)
我实际上也使用registerTypeHierarchyAdapter方法完成了上述操作，但这似乎需要实现自定义的DogAdapter和CatAdapter序列化器/反序列化器类，这在你想向Dog或Cat添加另一个字段时很难维护。
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