Add default KeyDeserializer for value class

pom.xml

@@ -251,6 +251,7 @@
                             <exclude>
                                 com.fasterxml.jackson.module.kotlin.KotlinNamesAnnotationIntrospector#KotlinNamesAnnotationIntrospector(com.fasterxml.jackson.module.kotlin.ReflectionCache,boolean)
                             </exclude>
+                            <exclude>com.fasterxml.jackson.module.kotlin.KotlinKeyDeserializers#INSTANCE</exclude>
                         </excludes>
                     </parameter>
                 </configuration>

release-notes/CREDITS-2.x

@@ -18,6 +18,7 @@ Contributors:
 # 2.19.0 (not yet released)
 
 WrongWrong (@k163377)
+* #910: Add default KeyDeserializer for value class
 * #885: Performance improvement of strictNullChecks
 * #884: Changed the base class of MissingKotlinParameterException to InvalidNullException
 * #878: Fix for #876

release-notes/VERSION-2.x

@@ -18,6 +18,8 @@ Co-maintainers:
 
 2.19.0 (not yet released)
 
+#910: A default `KeySerializer` for `value class` has been added.
+ This eliminates the need to have a custom `KeySerializer` for each `value class` when using it as a key in a `Map`, if only simple boxing is needed.
 #889: Kotlin has been upgraded to 1.9.25.
 #885: A new `StrictNullChecks` option(KotlinFeature.NewStrictNullChecks) has been added which greatly improves throughput.
  Benchmarks show a consistent throughput drop of less than 2% when enabled (prior to the improvement, the worst throughput drop was more than 30%).

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinKeyDeserializers.kt

@@ -5,6 +5,11 @@ import com.fasterxml.jackson.core.exc.InputCoercionException
 import com.fasterxml.jackson.databind.*
 import com.fasterxml.jackson.databind.deser.std.StdKeyDeserializer
 import com.fasterxml.jackson.databind.deser.std.StdKeyDeserializers
+import com.fasterxml.jackson.databind.exc.InvalidDefinitionException
+import java.lang.reflect.Method
+import kotlin.reflect.KClass
+import kotlin.reflect.full.primaryConstructor
+import kotlin.reflect.jvm.javaMethod
 
 // The reason why key is treated as nullable is to match the tentative behavior of StdKeyDeserializer.
 // If StdKeyDeserializer is modified, need to modify this too.
@@ -65,18 +70,68 @@ internal object ULongKeyDeserializer : StdKeyDeserializer(TYPE_LONG, ULong::clas
     }
 }
 
-internal object KotlinKeyDeserializers : StdKeyDeserializers() {
-    private fun readResolve(): Any = KotlinKeyDeserializers
+// The implementation is designed to be compatible with various creators, just in case.
+internal class ValueClassKeyDeserializer<S, D : Any>(
+    private val creator: Method,
+    private val converter: ValueClassBoxConverter<S, D>
+) : KeyDeserializer() {
+    private val unboxedClass: Class<*> = creator.parameterTypes[0]
 
+    init {
+        creator.apply { if (!this.isAccessible) this.isAccessible = true }
+    }
+
+    // Based on databind error
+    // https://github.com/FasterXML/jackson-databind/blob/341f8d360a5f10b5e609d6ee0ea023bf597ce98a/src/main/java/com/fasterxml/jackson/databind/deser/DeserializerCache.java#L624
+    private fun errorMessage(boxedType: JavaType): String =
+        "Could not find (Map) Key deserializer for types wrapped in $boxedType"
+
+    override fun deserializeKey(key: String?, ctxt: DeserializationContext): Any {
+        val unboxedJavaType = ctxt.constructType(unboxedClass)
+
+        return try {
+            // findKeyDeserializer does not return null, and an exception will be thrown if not found.
+            val value = ctxt.findKeyDeserializer(unboxedJavaType, null).deserializeKey(key, ctxt)
+            @Suppress("UNCHECKED_CAST")
+            converter.convert(creator.invoke(null, value) as S)
+        } catch (e: InvalidDefinitionException) {
+            throw JsonMappingException.from(ctxt, errorMessage(ctxt.constructType(converter.boxedClass.java)), e)
+        }
+    }
+
+    companion object {
+        fun createOrNull(
+            boxedClass: KClass<*>,
+            cache: ReflectionCache
+        ): ValueClassKeyDeserializer<*, *>? {
+            // primaryConstructor.javaMethod for the value class returns constructor-impl
+            // Only primary constructor is allowed as creator, regardless of visibility.
+            // This is because it is based on the WrapsNullableValueClassBoxDeserializer.
+            // Also, as far as I could research, there was no such functionality as JsonKeyCreator,
+            // so it was not taken into account.
+            val creator = boxedClass.primaryConstructor?.javaMethod ?: return null
+            val converter = cache.getValueClassBoxConverter(creator.returnType, boxedClass)
+
+            return ValueClassKeyDeserializer(creator, converter)
+        }
+    }
+}
+
+internal class KotlinKeyDeserializers(private val cache: ReflectionCache) : StdKeyDeserializers() {
     override fun findKeyDeserializer(
         type: JavaType,
         config: DeserializationConfig?,
         beanDesc: BeanDescription?
-    ): KeyDeserializer? = when (type.rawClass) {
-        UByte::class.java -> UByteKeyDeserializer
-        UShort::class.java -> UShortKeyDeserializer
-        UInt::class.java -> UIntKeyDeserializer
-        ULong::class.java -> ULongKeyDeserializer
-        else -> null
+    ): KeyDeserializer? {
+        val rawClass = type.rawClass
+
+        return when {
+            rawClass == UByte::class.java -> UByteKeyDeserializer
+            rawClass == UShort::class.java -> UShortKeyDeserializer
+            rawClass == UInt::class.java -> UIntKeyDeserializer
+            rawClass == ULong::class.java -> ULongKeyDeserializer
+            rawClass.isUnboxableValueClass() -> ValueClassKeyDeserializer.createOrNull(rawClass.kotlin, cache)
+            else -> null
+        }
     }
 }

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt

@@ -130,7 +130,7 @@ class KotlinModule private constructor(
         )
 
         context.addDeserializers(KotlinDeserializers(cache, useJavaDurationConversion))
-        context.addKeyDeserializers(KotlinKeyDeserializers)
+        context.addKeyDeserializers(KotlinKeyDeserializers(cache))
         context.addSerializers(KotlinSerializers())
         context.addKeySerializers(KotlinKeySerializers())
 

src/test/kotlin/com/fasterxml/jackson/module/kotlin/kogeraIntegration/deser/valueClass/ValueClasses.kt

@@ -4,12 +4,17 @@ import com.fasterxml.jackson.core.JsonParser
 import com.fasterxml.jackson.databind.DeserializationContext
 import com.fasterxml.jackson.databind.deser.std.StdDeserializer
 import com.fasterxml.jackson.module.kotlin.WrapsNullableValueClassDeserializer
+import com.fasterxml.jackson.databind.KeyDeserializer as JacksonKeyDeserializer
 
 @JvmInline
 value class Primitive(val v: Int) {
     class Deserializer : StdDeserializer<Primitive>(Primitive::class.java) {
         override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Primitive = Primitive(p.intValue + 100)
     }
+
+    class KeyDeserializer : JacksonKeyDeserializer() {
+        override fun deserializeKey(key: String, ctxt: DeserializationContext) = Primitive(key.toInt() + 100)
+    }
 }
 
 @JvmInline
@@ -18,6 +23,10 @@ value class NonNullObject(val v: String) {
         override fun deserialize(p: JsonParser, ctxt: DeserializationContext): NonNullObject =
             NonNullObject(p.valueAsString + "-deser")
     }
+
+    class KeyDeserializer : JacksonKeyDeserializer() {
+        override fun deserializeKey(key: String, ctxt: DeserializationContext) = NonNullObject("$key-deser")
+    }
 }
 
 @JvmInline
@@ -28,4 +37,8 @@ value class NullableObject(val v: String?) {
 
         override fun getBoxedNullValue(): NullableObject = NullableObject("null-value-deser")
     }
+
+    class KeyDeserializer : JacksonKeyDeserializer() {
+        override fun deserializeKey(key: String, ctxt: DeserializationContext) = NullableObject("$key-deser")
+    }
 }

src/test/kotlin/com/fasterxml/jackson/module/kotlin/kogeraIntegration/deser/valueClass/mapKey/WithoutCustomDeserializeMethodTest.kt

@@ -0,0 +1,117 @@
+package com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.mapKey
+
+import com.fasterxml.jackson.databind.DeserializationContext
+import com.fasterxml.jackson.databind.JsonMappingException
+import com.fasterxml.jackson.databind.exc.InvalidDefinitionException
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.kotlin.defaultMapper
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.NonNullObject
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.NullableObject
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.Primitive
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import java.lang.reflect.InvocationTargetException
+import com.fasterxml.jackson.databind.KeyDeserializer as JacksonKeyDeserializer
+
+class WithoutCustomDeserializeMethodTest {
+    companion object {
+        val throwable = IllegalArgumentException("test")
+    }
+
+    @Nested
+    inner class DirectDeserialize {
+        @Test
+        fun primitive() {
+            val result = defaultMapper.readValue<Map<Primitive, String?>>("""{"1":null}""")
+            assertEquals(mapOf(Primitive(1) to null), result)
+        }
+
+        @Test
+        fun nonNullObject() {
+            val result = defaultMapper.readValue<Map<NonNullObject, String?>>("""{"foo":null}""")
+            assertEquals(mapOf(NonNullObject("foo") to null), result)
+        }
+
+        @Test
+        fun nullableObject() {
+            val result = defaultMapper.readValue<Map<NullableObject, String?>>("""{"bar":null}""")
+            assertEquals(mapOf(NullableObject("bar") to null), result)
+        }
+    }
+
+    data class Dst(
+        val p: Map<Primitive, String?>,
+        val nn: Map<NonNullObject, String?>,
+        val n: Map<NullableObject, String?>
+    )
+
+    @Test
+    fun wrapped() {
+        val src = """
+            {
+              "p":{"1":null},
+              "nn":{"foo":null},
+              "n":{"bar":null}
+            }
+        """.trimIndent()
+        val result = defaultMapper.readValue<Dst>(src)
+        val expected = Dst(
+            mapOf(Primitive(1) to null),
+            mapOf(NonNullObject("foo") to null),
+            mapOf(NullableObject("bar") to null)
+        )
+
+        assertEquals(expected, result)
+    }
+
+    @JvmInline
+    value class HasCheckConstructor(val value: Int) {
+        init {
+            if (value < 0) throw throwable
+        }
+    }
+
+    @Test
+    fun callConstructorCheckTest() {
+        val e = assertThrows<InvocationTargetException> {
+            defaultMapper.readValue<Map<HasCheckConstructor, String?>>("""{"-1":null}""")
+        }
+        assertTrue(e.cause === throwable)
+    }
+
+    data class Wrapped(val first: String, val second: String) {
+        class KeyDeserializer : JacksonKeyDeserializer() {
+            override fun deserializeKey(key: String, ctxt: DeserializationContext) =
+                key.split("-").let { Wrapped(it[0], it[1]) }
+        }
+    }
+
+    @JvmInline
+    value class Wrapper(val w: Wrapped)
+
+    @Test
+    fun wrappedCustomObject() {
+        // If a type that cannot be deserialized is specified, the default is an error.
+        val thrown = assertThrows<JsonMappingException> {
+            defaultMapper.readValue<Map<Wrapper, String?>>("""{"foo-bar":null}""")
+        }
+        assertTrue(thrown.cause is InvalidDefinitionException)
+
+        val mapper = jacksonObjectMapper()
+            .registerModule(
+                object : SimpleModule() {
+                    init { addKeyDeserializer(Wrapped::class.java, Wrapped.KeyDeserializer()) }
+                }
+            )
+
+        val result = mapper.readValue<Map<Wrapper, String?>>("""{"foo-bar":null}""")
+        val expected = mapOf(Wrapper(Wrapped("foo", "bar")) to null)
+
+        assertEquals(expected, result)
+    }
+}

src/test/kotlin/com/fasterxml/jackson/module/kotlin/kogeraIntegration/deser/valueClass/mapKey/keyDeserializer/SpecifiedForObjectMapperTest.kt

@@ -0,0 +1,70 @@
+package com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.mapKey.keyDeserializer
+
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.NonNullObject
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.NullableObject
+import com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.Primitive
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+
+class SpecifiedForObjectMapperTest {
+    companion object {
+        val mapper = jacksonObjectMapper().apply {
+            val module = SimpleModule().apply {
+                this.addKeyDeserializer(Primitive::class.java, Primitive.KeyDeserializer())
+                this.addKeyDeserializer(NonNullObject::class.java, NonNullObject.KeyDeserializer())
+                this.addKeyDeserializer(NullableObject::class.java, NullableObject.KeyDeserializer())
+            }
+            this.registerModule(module)
+        }
+    }
+
+    @Nested
+    inner class DirectDeserialize {
+        @Test
+        fun primitive() {
+            val result = mapper.readValue<Map<Primitive, String?>>("""{"1":null}""")
+            assertEquals(mapOf(Primitive(101) to null), result)
+        }
+
+        @Test
+        fun nonNullObject() {
+            val result = mapper.readValue<Map<NonNullObject, String?>>("""{"foo":null}""")
+            assertEquals(mapOf(NonNullObject("foo-deser") to null), result)
+        }
+
+        @Test
+        fun nullableObject() {
+            val result = mapper.readValue<Map<NullableObject, String?>>("""{"bar":null}""")
+            assertEquals(mapOf(NullableObject("bar-deser") to null), result)
+        }
+    }
+
+    data class Dst(
+        val p: Map<Primitive, String?>,
+        val nn: Map<NonNullObject, String?>,
+        val n: Map<NullableObject, String?>
+    )
+
+    @Test
+    fun wrapped() {
+        val src = """
+            {
+              "p":{"1":null},
+              "nn":{"foo":null},
+              "n":{"bar":null}
+            }
+        """.trimIndent()
+        val result = mapper.readValue<Dst>(src)
+        val expected = Dst(
+            mapOf(Primitive(101) to null),
+            mapOf(NonNullObject("foo-deser") to null),
+            mapOf(NullableObject("bar-deser") to null)
+        )
+
+        assertEquals(expected, result)
+    }
+}

src/test/kotlin/com/fasterxml/jackson/module/kotlin/kogeraIntegration/deser/valueClass/mapKey/keyDeserializer/byAnnotation/SpecifiedForClassTest.kt

@@ -0,0 +1,37 @@
+package com.fasterxml.jackson.module.kotlin.kogeraIntegration.deser.valueClass.mapKey.keyDeserializer.byAnnotation
+
+import com.fasterxml.jackson.databind.DeserializationContext
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize
+import com.fasterxml.jackson.module.kotlin.defaultMapper
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import com.fasterxml.jackson.databind.KeyDeserializer as JacksonKeyDeserializer
+
+class SpecifiedForClassTest {
+    @JsonDeserialize(keyUsing = Value.KeyDeserializer::class)
+    @JvmInline
+    value class Value(val v: Int) {
+        class KeyDeserializer : JacksonKeyDeserializer() {
+            override fun deserializeKey(key: String, ctxt: DeserializationContext) = Value(key.toInt() + 100)
+        }
+    }
+
+    @Test
+    fun directDeserTest() {
+        val result = defaultMapper.readValue<Map<Value, String?>>("""{"1":null}""")
+
+        assertEquals(mapOf(Value(101) to null), result)
+    }
+
+    data class Wrapper(val v: Map<Value, String?>)
+
+    @Test
+    fun paramDeserTest() {
+        val mapper = jacksonObjectMapper()
+        val result = mapper.readValue<Wrapper>("""{"v":{"1":null}}""")
+
+        assertEquals(Wrapper(mapOf(Value(101) to null)), result)
+    }
+}