@JsonClass(generateAdapter = true)
data class DefaultAll(
val name: String = "me",
val age: Int = 17
这种情况下，gson 和 moshi都可以正常解析 “{}” json字符
部分字段有默认值
@JsonClass(generateAdapter = true)
data class DefaultPart(
val name: String = "me",
val gender: String = "male",
val age: Int
// 针对以下json gson忽略name，gender属性的默认值，而moshi可以正常解析
val json = """{"age": 17}"""
internal class KotlinJsonAdapter<T>(
val constructor: KFunction<T>,
// 所有属性的bindingAdpter
val allBindings: List<Binding<T, Any?>?>,
// 忽略反序列化的属性
val nonIgnoredBindings: List<Binding<T, Any?>>,
// 反射类得来的属性列表
val options: JsonReader.Options
) : JsonAdapter<T>() {
override fun fromJson(reader: JsonReader): T {
val constructorSize = constructor.parameters.size
// Read each value into its slot in the array.
val values = Array<Any?>(allBindings.size) { ABSENT_VALUE }
reader.beginObject()
while (reader.hasNext()) {
//通过reader获取到Json 属性对应的类属性的索引
val index = reader.selectName(options)
if (index == -1) {
reader.skipName()
reader.skipValue()
continue
//拿到该属性的binding
val binding = nonIgnoredBindings[index]
// 拿到属性值的索引
val propertyIndex = binding.propertyIndex
if (values[propertyIndex] !== ABSENT_VALUE) {
throw JsonDataException(
"Multiple values for '${binding.property.name}' at ${reader.path}"
// 递归的方式，初始化属性值
values[propertyIndex] = binding.adapter.fromJson(reader)
// 关键的地方1
// 判断 初始化的属性值是否为null ，如果是null ，代表这json字符串中的体现为 age:null
if (values[propertyIndex] == null && !binding.property.returnType.isMarkedNullable) {
// 抛出Non-null value age was null at $ 异常
throw Util.unexpectedNull(
binding.property.name,
binding.jsonName,
reader
reader.endObject()
// 关键的地方2
// 初始化剩下json中没有的属性
// Confirm all parameters are present, optional, or nullable.
// 是否调用全属性构造函数标志
var isFullInitialized = allBindings.size == constructorSize
for (i in 0 until constructorSize) {
if (values[i] === ABSENT_VALUE) {
// 如果等于ABSENT_VALUE，表示该属性没有初始化
when {
// 如果该属性是可缺失的，即该属性有默认值，这不需要处理，全属性构造函数标志为false
constructor.parameters[i].isOptional -> isFullInitialized = false
// 如果该属性是可空的，这直接赋值为null
constructor.parameters[i].type.isMarkedNullable -> values[i] = null // Replace absent with null.
// 剩下的则是属性没有默认值，也不允许为空，如上例，age属性
// 抛出Required value age missing at $ 异常
else -> throw Util.missingProperty(
constructor.parameters[i].name,
allBindings[i]?.jsonName,
reader
// Call the constructor using a Map so that absent optionals get defaults.
val result = if (isFullInitialized) {
constructor.call(*values)
} else {
constructor.callBy(IndexedParameterMap(constructor.parameters, values))
// Set remaining properties.
for (i in constructorSize until allBindings.size) {
val binding = allBindings[i]!!
val value = values[i]
binding.set(result, value)
return result
override fun toJson(writer: JsonWriter, value: T?) {
if (value == null) throw NullPointerException("value == null")
writer.beginObject()
for (binding in allBindings) {
if (binding == null) continue // Skip constructor parameters that aren't properties.
writer.name(binding.jsonName)
binding.adapter.toJson(writer, binding.get(value))
writer.endObject()
通过代码的分析，是不是可以在两个关键的逻辑点做以下修改
// 关键的地方1
// 判断 初始化的属性值是否为null ，如果是null ，代表这json字符串中的体现为 age:null
if (values[propertyIndex] == null && !binding.property.returnType.isMarkedNullable) {
// 抛出Non-null value age was null at $ 异常
//throw Util.unexpectedNull(
// binding.property.name,
// binding.jsonName,
// reader
// age:null 重置为ABSENT_VALUE值，交由最后初始化剩下json中没有的属性的时候去初始化
values[propertyIndex] = ABSENT_VALUE
// 关键的地方2
// 初始化剩下json中没有的属性
// Confirm all parameters are present, optional, or nullable.
// 是否调用全属性构造函数标志
var isFullInitialized = allBindings.size == constructorSize
for (i in 0 until constructorSize) {
if (values[i] === ABSENT_VALUE) {
// 如果等于ABSENT_VALUE，表示该属性没有初始化
when {
// 如果该属性是可缺失的，即该属性有默认值，这不需要处理，全属性构造函数标志为false
constructor.parameters[i].isOptional -> isFullInitialized = false
// 如果该属性是可空的，这直接赋值为null
constructor.parameters[i].type.isMarkedNullable -> values[i] = null // Replace absent with null.
// 剩下的则是属性没有默认值，也不允许为空，如上例，age属性
// 抛出Required value age missing at $ 异常
else ->{
//throw Util.missingProperty(
//constructor.parameters[i].name,
//allBindings[i]?.jsonName,
//reader
// 填充默认
val index = options.strings().indexOf(constructor.parameters[i].name)
val binding = nonIgnoredBindings[index]
val propertyIndex = binding.propertyIndex
// 为该属性初始化默认值
values[propertyIndex] = fullDefault(binding)
private fun fullDefault(binding: Binding<T, Any?>): Any? {
return when (binding.property.returnType.classifier) {
Int::class -> 0
String::class -> ""
Boolean::class -> false
Byte::class -> 0.toByte()
Char::class -> Char.MIN_VALUE
Double::class -> 0.0
Float::class -> 0f
Long::class -> 0L
Short::class -> 0.toShort()
// 过滤递归类初始化，这种会导致死循环
constructor.returnType.classifier -> {
val message =
"Unsolvable as for: ${binding.property.returnType.classifier}(value:${binding.property.returnType.classifier})"
throw JsonDataException(message)
is Any -> {
// 如果是集合就初始化[],否则就是{}对象
if (Collection::class.java.isAssignableFrom(binding.property.returnType.javaType.rawType)) {
binding.adapter.fromJson("[]")
} else {
binding.adapter.fromJson("{}")
else -> {}
@JsonClass(generateAdapter = true)
data class DefaultPart(
val name: String,
val gender: String = "male",
val age: Int,
val action:Action
class Action(val ac:String)
最终Action也会产生一个Action(ac:"")的值
data class RestResponse<T>(
val code: Int,
val msg: String="",
val data: T?
fun isSuccess() = code == 1
fun checkData() = data != null
fun successRestData() = isSuccess() && checkData()
fun requsetData() = data!!
class TestD(val a:Int,val b:String,val c:Boolean,val d:List<Test> ) {
class Test(val a:Int,val b:String,val c:Boolean=true)
val s = """
"code":200,
"msg":"ok",
"data":[{"a":0,"c":false,"d":[{"b":null}]}]}
""".trimIndent()
val a :RestResponse<List<TestD>>? = s.fromJson()
