[TOC]
Moshi-kotlin-nullsafe 中文版
1. moshi-kotlin
moshi-kotlin support kotlin type safe check.
When parsing json, fields declared as non-null types may throw JsonDataException
- Missing property：
JsonDataException("Non-null value '%s' was null at %s") - Unexpected null value：
JsonDataException("Required value '%s' missing at %s")
For example:
data class User(
val name: String,
val age: Int,
val address: String
)
val moshi = Moshi.Builder()
.add(KotlinJsonAdapterFactory())
.build()
val json = """
{
"name": "Tom",
"age": 10
}
""".trimIndent()
// com.squareup.moshi.JsonDataException: Required value 'address' missing at $
moshi.adapter(User::class.java).fromJson(json)
2. moshi-kotlin-nullsafe
moshi-kotlin-nullsafe aims to solve the above problem.
When the declared non-null field is missing or null, the default value will be automatically filled.
| Type | Default value |
|---|---|
| Int | 0 |
| Char | 0.toChar() |
| Byte | 0.toByte() |
| Float | 0.toFloat() |
| Double | 0.toDouble() |
| Long | 0.toLong() |
| String | "" |
| Boolean | false |
| List | Collections.EMPTY_LIST |
| Map | Collections.EMPTY_MAP |
| Set | Collections.EMPTY_SET |
2.1 How to?
Step 1. Add the JitPack repository to your build file
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
Step 2. Add the dependency
dependencies {
implementation 'com.github.sparklexin:moshi-kotlin-nullsafe:${latest_version}'
}
2.2 Usage
data class User(
val name: String,
val age: Int,
val address: String
)
val moshi = Moshi.Builder()
.add(NullSafeStandardJsonAdapters.FACTORY)
.add(NullSafeKotlinJsonAdapterFactory())
.build()
val json = """
{
"name": "Tom",
"age": 10
}
""".trimIndent()
val user = moshi.adapter(User::class.java).fromJson(json)
// User(name=Tom, age=10, address=)
println(user)
retrofit2 converter-moshi
val nullSafeMoshi = Moshi.Builder()
.add(NullSafeStandardJsonAdapters.FACTORY)
.add(NullSafeKotlinJsonAdapterFactory())
.build()
val retrofit = Retrofit.Builder()
.baseUrl(API_URL)
.addConverterFactory(MoshiConverterFactory.create(nullSafeMoshi))
.build()
2.3 Customize
NullSafeKotlinJsonAdapterFactory uses BuildInDefaultValueProvider by default to provide default values:
internal class BuildInDefaultValueProvider : DefaultValueProvider {
override fun provideDefaultValue(kType: KType): Any? {
return when (kType.classifier) {
Int::class -> 0
Char::class -> 0.toChar()
Byte::class -> 0.toByte()
Float::class -> 0.toFloat()
Double::class -> 0.toDouble()
Long::class -> 0.toLong()
String::class -> ""
Boolean::class -> false
List::class -> Collections.EMPTY_LIST
Map::class -> Collections.EMPTY_MAP
Set::class -> Collections.EMPTY_SET
else -> null
}
}
}
Developers can use your own DefaultValueProvider to support more types.
class NullSafeKotlinJsonAdapterFactory(
private val providers: List<DefaultValueProvider> = listOf(),
private val useBuildInProviders: Boolean = true
)
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