java – Gson反序列化其Class实现的接口

1.创建一个将由其他应用程序界面扩展的基本界面.需要为所有接口和实现类创建单个反序列化器.

public interface Convertable {
     String getClassName();
}

2.创建功能界面和实现类.例如,让我们将它们命名为FooInterface和FooClass. FooInterface应该扩展Convertable接口.

FooInterface

public interface FooInterface extends Convertable {

}

FooClass

public class FooClass implements FooInterface {

    // DISCRIMINATOR FIELD
    private final String className;

    private String field1;

    private String field2;

    public FooClass() {
        this.className = getClass().getName();
    }

    public String getClassName() {
        return className;
    }

    public String getField1() {
        return field1;
    }

    public void setField1(String field1) {
        this.field1 = field1;
    }

    public String getField2() {
        return field2;
    }

    public void setField2(String field2) {
        this.field2 = field2;
    }

}

请注意,getClassName()返回的值用作将在Gson反序列化器(下一步)中用于初始化可返回实例的鉴别器字段.我假设您的序列化程序和反序列化程序类将驻留在同一个程序包中,即使它们位于不同的客户端和服务器应用程序中.如果没有,那么您将需要更改getClassInstance()实现,但这样做非常简单.

3.为您的所有应用程序实现自定义Gson Serializer

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;

public class ConvertableDeserializer<T extends Convertable> implements JsonDeserializer<T> {

    private static final String CLASSNAME = "className";

    public T deserialize(final JsonElement jsonElement,final Type type,final JsonDeserializationContext deserializationContext
                        ) throws JsonParseException {

        final JsonObject jsonObject = jsonElement.getAsJsonObject();
        final JsonPrimitive prim = (JsonPrimitive) jsonObject.get(CLASSNAME);
        final String className = prim.getAsString();
        final Class<T> clazz = getClassInstance(className);
        return deserializationContext.deserialize(jsonObject,clazz);
    }

    @SuppressWarnings("unchecked")
    public Class<T> getClassInstance(String className) {
        try {
            return (Class<T>) Class.forName(className);
        } catch (ClassNotFoundException cnfe) {
            throw new JsonParseException(cnfe.getMessage());
        }
    }

}

4.使用Gson注册Deserializer并初始化改造

private static GsonConverterFactory buildGsonConverter() {

        final GsonBuilder builder = new GsonBuilder();

        // Adding custom deserializers
        builder.registerTypeAdapter(FooInterface.class,new ConvertableDeserializer<FooInterface>());
        final Gson gson = builder.create();

        return GsonConverterFactory.create(myGson);
    }


    public void initRetrofit() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("REST_ENDPOINT")
                .addConverterFactory(buildGsonConverter())
                .client(httpClient)
                .build();
    }

如果需要,您可以为所有实现注册适配器,使用：

builder.registerTypeAdapter(Convertable.class,new ConvertableDeserializer<Convertable>());