问题描述
我想在 Kotlin Multiplatform 项目中使用 kotlinx.serialization 解码包含多态类结构中的对象列表的 json 字符串,但它仅适用于 JVM,不适用于 Native。这是一个最小的可重现示例:
@Serializable
abstract class Project {
abstract val name: String
}
@Serializable
@SerialName("BasicProject")
data class BasicProject(override val name: String): Project()
@Serializable
@SerialName("OwnedProject")
data class OwnedProject(override val name: String,val owner: String) : Project()
fun main() {
val data = Json.decodeFromString<List<Project>>("""
[
{"type":"BasicProject","name":"example"},{"type":"OwnedProject","name":"kotlinx.serialization","owner":"kotlin"}
]
"""))
}
这适用于 JVM,但在 Native 上抛出以下异常:
kotlinx.serialization.SerializationException: Serializer for class ‘Project’ is not found.
Mark the class as @Serializable or provide the serializer explicitly.
On Kotlin/Native explicitly declared serializer should be used for interfaces and enums without @Serializable annotation.message
这个问题之前已经在编码的上下文中讨论过,并且已经提出了一些解决方法,例如here,但我的问题是解码。是否有解决方法,或者我是否只需实现自己的 json 解析器?
解决方法
您需要明确传递尊重的序列化程序和serializersModule
:
object ListOfProjectSerializer : KSerializer<List<Project>> by ListSerializer(Project.serializer())
val module = SerializersModule {
polymorphic(Project::class) {
subclass(BasicProject::class)
subclass(OwnedProject::class)
}
}
fun main() {
val data = Json { serializersModule = module }.decodeFromString(
ListOfProjectSerializer,"""
[
{"type":"BasicProject","name":"example"},{"type":"OwnedProject","name":"kotlinx.serialization","owner":"kotlin"}
]
"""
)
}