RuntimeTypeAdapterFactory 说“类型”未定义

Question

我正在处理一种情况，我需要反序列化多态类。

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Class Pen{\n  String name;\n  List<Animal> animals;\n}\n\n//Animal can be an interface or parent class: I am flexible\n\nClass Animal{\n  AnimalType type;//enum\n  int legs;\n}\n\nenum AnimalType{\n  dog,cat,pig,chicken;\n}\n\nClass AnimalDog extends Animal{\n  //\xe2\x80\xa6\n}\n\nClass AnimalCat extends Animal{\n  //\xe2\x80\xa6\n}\n\n\nClass AnimalPig extends Animal{\n  //\xe2\x80\xa6\n}\n

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然后我创建我的 Gson 实例

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public static Gson instanceUpperCamelCaseWithTypeAdapterFactory() {\n    if (null == sGsonUpperCamelCase) {\n        final RuntimeTypeAdapterFactory<Animal> typeFactory = RuntimeTypeAdapterFactory\n                .of(Animal.class, \xe2\x80\x9ctype")\n                .registerSubtype(AnimalDog.class, \xe2\x80\x9cdog\xe2\x80\x9d)\n                .registerSubtype(AnimalCat.class, \xe2\x80\x9ccat\xe2\x80\x9d)\n                .registerSubtype(AnimalPig.class, \xe2\x80\x9cpig\xe2\x80\x9d);\n\n        sGsonUpperCamelCase = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)\n                .registerTypeAdapterFactory(typeFactory).create();\n    }//the naming policy is because server sends me upper case fields whereas Java fields are lowercase.\n    return sGsonUpperCamelCase;\n}\n

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为了从包含动物列表的 json 中获取动物，我这样做

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List<Animal> animals = gson.fromJson(json, new TypeToken<List<Animal>>() {}.getType());\n

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我对Gson完全是个新手。完全地。那么，在不让我太困惑的情况下，我该如何解决这个问题呢？

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错误跟踪：

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com.google.gson.JsonParseException: cannot deserialize class com.company.appname.data.model.Animal because it does not define a field named type\ncom.company.appname.utils.RuntimeTypeAdapterFactory$1.read(RuntimeTypeAdapterFactory.java:204)\ncom.google.gson.TypeAdapter$1.read(TypeAdapter.java:199)\ncom.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)\ncom.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)\ncom.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)\ncom.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:117)\ncom.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:217)\ncom.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)\ncom.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)\ncom.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)\ncom.google.gson.Gson.fromJson(Gson.java:861)\ncom.google.gson.Gson.fromJson(Gson.java:826)\ncom.google.gson.Gson.fromJson(Gson.java:775)\n

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我通过在线验证器运行json，没有问题。它有许多项目。这里我展示两个。

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{\xe2\x80\x9cAnimals\xe2\x80\x9d:[{  \n           \xe2\x80\x9cid":9,\n           \xe2\x80\x9ctype\xe2\x80\x9d:\xe2\x80\x9ddog\xe2\x80\x9d,\n           \xe2\x80\x9cname\xe2\x80\x9d:\xe2\x80\x9dmaximus\xe2\x80\x9d\n        },\n        {  \n           \xe2\x80\x9cid":10,\n           \xe2\x80\x9ctype\xe2\x80\x9d:\xe2\x80\x9dcat\xe2\x80\x9d,\n           \xe2\x80\x9cname\xe2\x80\x9d:\xe2\x80\x9dmeowy\xe2\x80\x9d,\n           \xe2\x80\x9cyarns\xe2\x80\x9d:5,\n           \xe2\x80\x9cnice\xe2\x80\x9d:true\n        }]}\n

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Answer 1

RuntimeTypeAdapterFactory.class 行号 -> 203

需要更换

JsonElement labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);

和

JsonElement labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName);

Answer 2

我在 RuntimeTypeAdapterFactory 中发现了错误（第 185 行，方法 create()），并解决了此问题，需要替换

if (type.getRawType() != baseType)

和

if (null == type || !baseType.isAssignableFrom(type.getRawType()))

然后 RuntimeTypeAdapterFactory 按预期工作。

请参阅链接已注册问题以及建议的修复