是的,理想情况下,null
而不是{}
更方便解析,但有时您只需要使用后端发送给您的内容
我想到了2个解决方案。
- 更简单,特定于您使用地图的情况:
import kotlinx.serialization.decodeFromString
import kotlinx.serialization.json.Json
import org.junit.Assert.assertEquals
import org.junit.Assert.assertTrue
import org.junit.Test
class ThingMapSerializerTest {
@Test
fun `should deserialize to non empty map`() {
val thingMap: Map<String, String> =
Json.decodeFromString("""{"id":"ABC1","status":"A_STATUS"}""")
assertTrue(thingMap.isNotEmpty())
assertEquals("ABC1", thingMap["id"])
assertEquals("A_STATUS", thingMap["status"])
}
@Test
fun `should deserialize to empty map`() {
val thingMap: Map<String, String> = Json.decodeFromString("{}")
assertTrue(thingMap.isEmpty())
}
}
- 更复杂但更通用,适用于值类型的任何组合。我推荐具有显式空值的密封类,而不是具有空默认值的数据类:
import kotlinx.serialization.KSerializer
import kotlinx.serialization.SerializationException
import kotlinx.serialization.descriptors.SerialDescriptor
import kotlinx.serialization.descriptors.buildClassSerialDescriptor
import kotlinx.serialization.descriptors.serialDescriptor
import kotlinx.serialization.encoding.CompositeDecoder
import kotlinx.serialization.encoding.Decoder
import kotlinx.serialization.encoding.Encoder
import kotlinx.serialization.encoding.decodeStructure
import kotlinx.serialization.json.Json
import org.junit.Assert.assertEquals
import org.junit.Test
class ThingSerializerTest {
@Test
fun `should deserialize to thing`() {
val thing: OptionalThing =
Json.decodeFromString(
OptionalThing.ThingSerializer,
"""{"id":"ABC1","status":"A_STATUS"}"""
)
assertEquals(OptionalThing.Thing(id = "ABC1", status = "A_STATUS"), thing)
}
@Test
fun `should deserialize to empty`() {
val thing: OptionalThing =
Json.decodeFromString(OptionalThing.ThingSerializer, "{}")
assertEquals(OptionalThing.Empty, thing)
}
sealed class OptionalThing {
data class Thing(val id: String = "", val status: String = "") : OptionalThing()
object Empty : OptionalThing()
object ThingSerializer : KSerializer<OptionalThing> {
override val descriptor: SerialDescriptor =
buildClassSerialDescriptor("your.app.package.OptionalThing") {
element("id", serialDescriptor<String>(), isOptional = true)
element("status", serialDescriptor<String>(), isOptional = true)
}
override fun deserialize(decoder: Decoder): OptionalThing {
decoder.decodeStructure(descriptor) {
var id: String? = null
var status: String? = null
loop@ while (true) {
when (val index = decodeElementIndex(descriptor)) {
CompositeDecoder.DECODE_DONE -> break@loop
0 -> id = decodeStringElement(descriptor, index = 0)
1 -> status = decodeStringElement(descriptor, index = 1)
else -> throw SerializationException("Unexpected index $index")
}
}
return if (id != null && status != null) Thing(id, status)
else Empty
}
}
override fun serialize(encoder: Encoder, value: OptionalThing) {
TODO("Not implemented, not needed")
}
}
}
}
当 'Thing' 是 json 对象中的一个字段时:
"thing":{"id":"ABC1","status":"A_STATUS"} // could be {}
你可以这样注释属性:
@Serializable(with = OptionalThing.ThingSerializer::class)
val thing: OptionalThing
测试:
classpath "org.jetbrains.kotlin:kotlin-serialization:1.4.10"
implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:1.0.1"