From cf5281cd383a9753c831502d51a4e19aaecb7434 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Mon, 17 Jul 2023 15:35:11 +0200
Subject: [PATCH 01/16] Handle `kotlin.time.Duration` as `java.time.Duration`

Adds converter and deserializer which bridges conversions between `kotlin.time.Duration` and `java.time.Duration`.

Notes:
* later Kotlin version adds dedicated method `kotlin.time.Duration.toJavaDuration()` which can be used instead ISO parsing (in converter)
* ...and adds dedicated extension method `java.time.Duration.toKotlinDuration()` which can be used instead ISO parsing (in deserializer)
---
 pom.xml                                       |  6 ++
 .../jackson/module/kotlin/Converters.kt       |  6 ++
 .../kotlin/KotlinAnnotationIntrospector.kt    | 12 ++-
 .../module/kotlin/KotlinDeserializers.kt      |  8 ++
 .../module/kotlin/test/DurationTests.kt       | 79 +++++++++++++++++++
 5 files changed, 107 insertions(+), 4 deletions(-)
 create mode 100644 src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt

diff --git a/pom.xml b/pom.xml
index 0ef4d2936..accfd7e10 100644
--- a/pom.xml
+++ b/pom.xml
@@ -121,6 +121,12 @@
             <artifactId>jackson-dataformat-xml</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <!-- needed for kotlin.time.Duration converter test -->
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index 716032518..7f5ea3efd 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -5,6 +5,8 @@ import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
 import com.fasterxml.jackson.databind.type.TypeFactory
 import com.fasterxml.jackson.databind.util.StdConverter
 import kotlin.reflect.KClass
+import java.time.Duration as JavaDuration
+import kotlin.time.Duration as KotlinDuration
 
 internal class SequenceToIteratorConverter(private val input: JavaType) : StdConverter<Sequence<*>, Iterator<*>>() {
     override fun convert(value: Sequence<*>): Iterator<*> = value.iterator()
@@ -16,6 +18,10 @@ internal class SequenceToIteratorConverter(private val input: JavaType) : StdCon
         ?: typeFactory.constructType(Iterator::class.java)
 }
 
+internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, JavaDuration>() {
+    override fun convert(value: KotlinDuration): JavaDuration = JavaDuration.parse(value.toIsoString())
+}
+
 // S is nullable because value corresponds to a nullable value class
 // @see KotlinNamesAnnotationIntrospector.findNullSerializer
 internal class ValueClassBoxConverter<S : Any?, D : Any>(
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index a9b53951d..10e3f08f3 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -8,7 +8,6 @@ import com.fasterxml.jackson.databind.Module
 import com.fasterxml.jackson.databind.cfg.MapperConfig
 import com.fasterxml.jackson.databind.introspect.*
 import com.fasterxml.jackson.databind.jsontype.NamedType
-import com.fasterxml.jackson.databind.ser.std.StdSerializer
 import com.fasterxml.jackson.databind.util.Converter
 import java.lang.reflect.AccessibleObject
 import java.lang.reflect.Constructor
@@ -23,6 +22,7 @@ import kotlin.reflect.full.createType
 import kotlin.reflect.full.declaredMemberProperties
 import kotlin.reflect.full.memberProperties
 import kotlin.reflect.jvm.*
+import kotlin.time.Duration
 
 
 internal class KotlinAnnotationIntrospector(private val context: Module.SetupContext,
@@ -68,9 +68,13 @@ internal class KotlinAnnotationIntrospector(private val context: Module.SetupCon
         // Find a converter to handle the case where the getter returns an unboxed value from the value class.
         is AnnotatedMethod -> cache.findValueClassReturnType(a)
             ?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
-        is AnnotatedClass -> a
-            .takeIf { Sequence::class.java.isAssignableFrom(it.rawType) }
-            ?.let { SequenceToIteratorConverter(it.type) }
+        is AnnotatedClass -> lookupKotlinTypeConverter(a)
+        else -> null
+    }
+
+    private fun lookupKotlinTypeConverter(a: AnnotatedClass) = when {
+        Sequence::class.java.isAssignableFrom(a.rawType) -> SequenceToIteratorConverter(a.type)
+        Duration::class.java.isAssignableFrom(a.rawType) -> KotlinToJavaDurationConverter
         else -> null
     }
 
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
index 0bceb64a0..0006588c1 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
@@ -10,6 +10,7 @@ import com.fasterxml.jackson.databind.JavaType
 import com.fasterxml.jackson.databind.JsonDeserializer
 import com.fasterxml.jackson.databind.deser.Deserializers
 import com.fasterxml.jackson.databind.deser.std.StdDeserializer
+import kotlin.time.Duration
 
 object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java) {
     override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Sequence<*> {
@@ -17,6 +18,12 @@ object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java)
     }
 }
 
+internal object DurationDeserializer : StdDeserializer<Duration>(Duration::class.java) {
+    override fun deserialize(p: JsonParser, ctxt: DeserializationContext) = ctxt
+        .readValue(p, java.time.Duration::class.java)
+        ?.let { Duration.parseIsoString(it.toString()) }
+}
+
 object RegexDeserializer : StdDeserializer<Regex>(Regex::class.java) {
     override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Regex {
         val node = ctxt.readTree(p)
@@ -94,6 +101,7 @@ internal class KotlinDeserializers : Deserializers.Base() {
             type.rawClass == UShort::class.java -> UShortDeserializer
             type.rawClass == UInt::class.java -> UIntDeserializer
             type.rawClass == ULong::class.java -> ULongDeserializer
+            type.rawClass == Duration::class.java -> DurationDeserializer
             else -> null
         }
     }
diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
new file mode 100644
index 000000000..5f7987e0a
--- /dev/null
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -0,0 +1,79 @@
+package com.fasterxml.jackson.module.kotlin.test
+
+import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import org.junit.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.hours
+
+class DurationTests {
+    @Test
+    fun `should serialize Kotlin duration using Java time module`() {
+        val mapper = jacksonObjectMapper()
+            .registerModule(JavaTimeModule())
+            .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
+
+        val result = mapper.writeValueAsString(1.hours)
+
+        assertEquals("\"PT1H\"", result)
+    }
+
+    @Test
+    fun `should deserialize Kotlin duration`() {
+        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+
+        val result = mapper.readValue<Duration>("\"PT1H\"")
+
+        assertEquals(1.hours, result)
+    }
+
+    @Test
+    fun `should serialize Kotlin duration inside list using Java time module`() {
+        val mapper = jacksonObjectMapper()
+            .registerModule(JavaTimeModule())
+            .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
+
+        val result = mapper.writeValueAsString(listOf(1.hours, 2.hours, 3.hours))
+
+        assertEquals("""["PT1H","PT2H","PT3H"]""", result)
+    }
+
+    @Test
+    fun `should deserialize Kotlin duration inside list`() {
+        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+
+        val result = mapper.readValue<List<Duration>>("""["PT1H","PT2H","PT3H"]""")
+
+        assertContentEquals(listOf(1.hours, 2.hours, 3.hours), result)
+    }
+
+    @Test
+    fun `should serialize Kotlin duration inside map using Java time module`() {
+        val mapper = jacksonObjectMapper()
+            .registerModule(JavaTimeModule())
+            .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
+
+        val result = mapper.writeValueAsString(mapOf(
+            "a" to 1.hours,
+            "b" to 2.hours,
+            "c" to 3.hours
+        ))
+
+        assertEquals("""{"a":"PT1H","b":"PT2H","c":"PT3H"}""", result)
+    }
+
+    @Test
+    fun `should deserialize Kotlin duration inside map`() {
+        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+
+        val result = mapper.readValue<Map<String, Duration>>("""{"a":"PT1H","b":"PT2H","c":"PT3H"}""")
+
+        assertEquals(result["a"], 1.hours)
+        assertEquals(result["b"], 2.hours)
+        assertEquals(result["c"], 3.hours)
+    }
+}
\ No newline at end of file

From 7a61b3fcbdda228829101a33a3ad82cfd9fb6d5b Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Mon, 17 Jul 2023 16:39:00 +0200
Subject: [PATCH 02/16] Add Duration tests for data class

In order to properly deserialize data class with duration following hacks are needed:
* class need to have explicit static factory annotated with ``@JsonCreator`, primary ctor won't cut it
* in data class definition value-class getter has to be annotated with Duration converter
---
 .../jackson/module/kotlin/Converters.kt       |  8 ++++
 .../module/kotlin/test/DurationTests.kt       | 39 +++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index 7f5ea3efd..03019a5ee 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -22,6 +22,14 @@ internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, Jav
     override fun convert(value: KotlinDuration): JavaDuration = JavaDuration.parse(value.toIsoString())
 }
 
+// this class is needed as workaround for deserialization
+// data classes with kotlin.time.Duration field which is a value class
+//
+// @see DurationTests.`should deserialize Kotlin duration inside data class`
+object JavaToKotlinDurationConverter : StdConverter<JavaDuration, KotlinDuration>() {
+    override fun convert(value: JavaDuration) = KotlinDuration.parseIsoString(value.toString())
+}
+
 // S is nullable because value corresponds to a nullable value class
 // @see KotlinNamesAnnotationIntrospector.findNullSerializer
 internal class ValueClassBoxConverter<S : Any?, D : Any>(
diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 5f7987e0a..58eb9a7cf 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -1,10 +1,15 @@
 package com.fasterxml.jackson.module.kotlin.test
 
+import com.fasterxml.jackson.annotation.JsonCreator
+import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
+import com.fasterxml.jackson.module.kotlin.JavaToKotlinDurationConverter
 import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import com.fasterxml.jackson.module.kotlin.readValue
 import org.junit.Test
+import java.time.Instant
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
 import kotlin.time.Duration
@@ -76,4 +81,38 @@ class DurationTests {
         assertEquals(result["b"], 2.hours)
         assertEquals(result["c"], 3.hours)
     }
+
+    data class Meeting(
+        val start: Instant,
+        @get:JsonDeserialize(converter = JavaToKotlinDurationConverter::class)
+        val duration: Duration,
+    ) {
+        companion object {
+            @JvmStatic
+            @JsonCreator
+            fun create(start: Instant, duration: Duration) = Meeting(start, duration)
+        }
+    }
+
+    @Test
+    fun `should serialize Kotlin duration inside data class using Java time module`() {
+        val mapper = jacksonObjectMapper()
+            .registerModule(JavaTimeModule())
+            .disable(WRITE_DATES_AS_TIMESTAMPS)
+            .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
+
+        val result = mapper.writeValueAsString(Meeting(Instant.parse("2023-06-20T14:00:00Z"), 1.5.hours))
+
+        assertEquals("""{"start":"2023-06-20T14:00:00Z","duration":"PT1H30M"}""", result)
+    }
+
+    @Test
+    fun `should deserialize Kotlin duration inside data class`() {
+        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+
+        val result = mapper.readValue<Meeting>("""{"start":"2023-06-20T14:00:00Z","duration":"PT1H30M"}""")
+
+        assertEquals(result.start, Instant.parse("2023-06-20T14:00:00Z"))
+        assertEquals(result.duration, 1.5.hours)
+    }
 }
\ No newline at end of file

From a1ba894c5af6cd965650c971bca023c1e785efa4 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 30 Jul 2023 10:03:42 +0200
Subject: [PATCH 03/16] Use conversion functions for Duration from stdlib-jdk8

---
 pom.xml                                               |  6 ++++++
 .../com/fasterxml/jackson/module/kotlin/Converters.kt |  3 ++-
 .../jackson/module/kotlin/KotlinDeserializers.kt      | 11 ++++++-----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/pom.xml b/pom.xml
index accfd7e10..41f9fef34 100644
--- a/pom.xml
+++ b/pom.xml
@@ -96,6 +96,12 @@
             <version>${version.kotlin}</version>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib-jdk8</artifactId>
+            <version>${version.kotlin}</version>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
             <artifactId>kotlin-reflect</artifactId>
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index 03019a5ee..ce24411b7 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -5,6 +5,7 @@ import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
 import com.fasterxml.jackson.databind.type.TypeFactory
 import com.fasterxml.jackson.databind.util.StdConverter
 import kotlin.reflect.KClass
+import kotlin.time.toJavaDuration
 import java.time.Duration as JavaDuration
 import kotlin.time.Duration as KotlinDuration
 
@@ -19,7 +20,7 @@ internal class SequenceToIteratorConverter(private val input: JavaType) : StdCon
 }
 
 internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, JavaDuration>() {
-    override fun convert(value: KotlinDuration): JavaDuration = JavaDuration.parse(value.toIsoString())
+    override fun convert(value: KotlinDuration) = value.toJavaDuration()
 }
 
 // this class is needed as workaround for deserialization
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
index 0006588c1..eb3c424ce 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
@@ -10,7 +10,9 @@ import com.fasterxml.jackson.databind.JavaType
 import com.fasterxml.jackson.databind.JsonDeserializer
 import com.fasterxml.jackson.databind.deser.Deserializers
 import com.fasterxml.jackson.databind.deser.std.StdDeserializer
-import kotlin.time.Duration
+import kotlin.time.toKotlinDuration
+import java.time.Duration as JavaDuration
+import kotlin.time.Duration as KotlinDuration
 
 object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java) {
     override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Sequence<*> {
@@ -18,10 +20,9 @@ object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java)
     }
 }
 
-internal object DurationDeserializer : StdDeserializer<Duration>(Duration::class.java) {
+internal object DurationDeserializer : StdDeserializer<KotlinDuration>(KotlinDuration::class.java) {
     override fun deserialize(p: JsonParser, ctxt: DeserializationContext) = ctxt
-        .readValue(p, java.time.Duration::class.java)
-        ?.let { Duration.parseIsoString(it.toString()) }
+        .readValue(p, JavaDuration::class.java)?.toKotlinDuration()
 }
 
 object RegexDeserializer : StdDeserializer<Regex>(Regex::class.java) {
@@ -101,7 +102,7 @@ internal class KotlinDeserializers : Deserializers.Base() {
             type.rawClass == UShort::class.java -> UShortDeserializer
             type.rawClass == UInt::class.java -> UIntDeserializer
             type.rawClass == ULong::class.java -> ULongDeserializer
-            type.rawClass == Duration::class.java -> DurationDeserializer
+            type.rawClass == KotlinDuration::class.java -> DurationDeserializer
             else -> null
         }
     }

From efeb17f223f5c14400e13f6d16444e179d0830c7 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 30 Jul 2023 11:49:37 +0200
Subject: [PATCH 04/16] Cleanup

---
 .../kotlin/KotlinAnnotationIntrospector.kt     | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index 10e3f08f3..035fa2b13 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -25,11 +25,13 @@ import kotlin.reflect.jvm.*
 import kotlin.time.Duration
 
 
-internal class KotlinAnnotationIntrospector(private val context: Module.SetupContext,
-                                            private val cache: ReflectionCache,
-                                            private val nullToEmptyCollection: Boolean,
-                                            private val nullToEmptyMap: Boolean,
-                                            private val nullIsSameAsDefault: Boolean) : NopAnnotationIntrospector() {
+internal class KotlinAnnotationIntrospector(
+    private val context: Module.SetupContext,
+    private val cache: ReflectionCache,
+    private val nullToEmptyCollection: Boolean,
+    private val nullToEmptyMap: Boolean,
+    private val nullIsSameAsDefault: Boolean,
+) : NopAnnotationIntrospector() {
 
     // TODO: implement nullIsSameAsDefault flag, which represents when TRUE that if something has a default value, it can be passed a null to default it
     //       this likely impacts this class to be accurate about what COULD be considered required
@@ -106,7 +108,7 @@ internal class KotlinAnnotationIntrospector(private val context: Module.SetupCon
 
     private fun AnnotatedField.hasRequiredMarker(): Boolean? {
         val byAnnotation = (member as Field).isRequiredByAnnotation()
-        val byNullability =  (member as Field).kotlinProperty?.returnType?.isRequired()
+        val byNullability = (member as Field).kotlinProperty?.returnType?.isRequired()
 
         return requiredAnnotationOrNullability(byAnnotation, byNullability)
     }
@@ -126,7 +128,7 @@ internal class KotlinAnnotationIntrospector(private val context: Module.SetupCon
     }
 
     private fun Method.isRequiredByAnnotation(): Boolean? {
-       return (this.annotations.firstOrNull { it.annotationClass.java == JsonProperty::class.java } as? JsonProperty)?.required
+        return (this.annotations.firstOrNull { it.annotationClass.java == JsonProperty::class.java } as? JsonProperty)?.required
     }
 
     // Since Kotlin's property has the same Type for each field, getter, and setter,
@@ -180,7 +182,7 @@ internal class KotlinAnnotationIntrospector(private val context: Module.SetupCon
     }
 
     private fun KFunction<*>.isMethodParameterRequired(index: Int): Boolean {
-        return isParameterRequired(index+1)
+        return isParameterRequired(index + 1)
     }
 
     private fun KFunction<*>.isParameterRequired(index: Int): Boolean {

From 58ca164de499e50a0c7c547c85b6ca6f3910c0c6 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 30 Jul 2023 11:54:35 +0200
Subject: [PATCH 05/16] Serialize Kotlin Duration in same way as Java

---
 .../jackson/module/kotlin/Converters.kt       |  2 +
 .../kotlin/KotlinAnnotationIntrospector.kt    | 17 +++++---
 .../module/kotlin/test/DurationTests.kt       | 43 ++++++++++++++++---
 3 files changed, 50 insertions(+), 12 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index ce24411b7..0d63c4519 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -21,6 +21,8 @@ internal class SequenceToIteratorConverter(private val input: JavaType) : StdCon
 
 internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, JavaDuration>() {
     override fun convert(value: KotlinDuration) = value.toJavaDuration()
+
+    val delegatingSerializer: StdDelegatingSerializer by lazy { StdDelegatingSerializer(this) }
 }
 
 // this class is needed as workaround for deserialization
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index 035fa2b13..7dfb4f87a 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -68,8 +68,7 @@ internal class KotlinAnnotationIntrospector(
 
     override fun findSerializationConverter(a: Annotated): Converter<*, *>? = when (a) {
         // Find a converter to handle the case where the getter returns an unboxed value from the value class.
-        is AnnotatedMethod -> cache.findValueClassReturnType(a)
-            ?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
+        is AnnotatedMethod -> a.ktClass()?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
         is AnnotatedClass -> lookupKotlinTypeConverter(a)
         else -> null
     }
@@ -87,10 +86,14 @@ internal class KotlinAnnotationIntrospector(
 
     // Perform proper serialization even if the value wrapped by the value class is null.
     // If value is a non-null object type, it must not be reboxing.
-    override fun findNullSerializer(am: Annotated): JsonSerializer<*>? = (am as? AnnotatedMethod)?.let { _ ->
-        cache.findValueClassReturnType(am)
-            ?.takeIf { it.requireRebox() }
-            ?.let { cache.getValueClassBoxConverter(am.rawReturnType, it).delegatingSerializer }
+    override fun findNullSerializer(am: Annotated): JsonSerializer<*>? = (am as? AnnotatedMethod)
+        ?.ktClass()
+        ?.takeIf { it.requireRebox() }
+        ?.let { cache.getValueClassBoxConverter(am.rawReturnType, it).delegatingSerializer }
+
+    override fun findSerializer(am: Annotated): Any? = when ((am as? AnnotatedMethod)?.ktClass()) {
+        Duration::class -> KotlinToJavaDurationConverter.delegatingSerializer
+        else -> super.findSerializer(am)
     }
 
     /**
@@ -177,6 +180,8 @@ internal class KotlinAnnotationIntrospector(
         return requiredAnnotationOrNullability(byAnnotation, byNullability)
     }
 
+    private fun AnnotatedMethod.ktClass() = cache.findValueClassReturnType(this)
+
     private fun KFunction<*>.isConstructorParameterRequired(index: Int): Boolean {
         return isParameterRequired(index)
     }
diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 58eb9a7cf..40c436df3 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -1,6 +1,8 @@
 package com.fasterxml.jackson.module.kotlin.test
 
 import com.fasterxml.jackson.annotation.JsonCreator
+import com.fasterxml.jackson.annotation.JsonFormat
+import com.fasterxml.jackson.annotation.JsonFormat.Shape.STRING
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
@@ -12,7 +14,8 @@ import org.junit.Test
 import java.time.Instant
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
-import kotlin.time.Duration
+import kotlin.time.Duration as KotlinDuration
+import java.time.Duration as JavaDuration
 import kotlin.time.Duration.Companion.hours
 
 class DurationTests {
@@ -31,7 +34,7 @@ class DurationTests {
     fun `should deserialize Kotlin duration`() {
         val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
 
-        val result = mapper.readValue<Duration>("\"PT1H\"")
+        val result = mapper.readValue<KotlinDuration>("\"PT1H\"")
 
         assertEquals(1.hours, result)
     }
@@ -51,7 +54,7 @@ class DurationTests {
     fun `should deserialize Kotlin duration inside list`() {
         val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
 
-        val result = mapper.readValue<List<Duration>>("""["PT1H","PT2H","PT3H"]""")
+        val result = mapper.readValue<List<KotlinDuration>>("""["PT1H","PT2H","PT3H"]""")
 
         assertContentEquals(listOf(1.hours, 2.hours, 3.hours), result)
     }
@@ -75,7 +78,7 @@ class DurationTests {
     fun `should deserialize Kotlin duration inside map`() {
         val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
 
-        val result = mapper.readValue<Map<String, Duration>>("""{"a":"PT1H","b":"PT2H","c":"PT3H"}""")
+        val result = mapper.readValue<Map<String, KotlinDuration>>("""{"a":"PT1H","b":"PT2H","c":"PT3H"}""")
 
         assertEquals(result["a"], 1.hours)
         assertEquals(result["b"], 2.hours)
@@ -85,12 +88,12 @@ class DurationTests {
     data class Meeting(
         val start: Instant,
         @get:JsonDeserialize(converter = JavaToKotlinDurationConverter::class)
-        val duration: Duration,
+        val duration: KotlinDuration,
     ) {
         companion object {
             @JvmStatic
             @JsonCreator
-            fun create(start: Instant, duration: Duration) = Meeting(start, duration)
+            fun create(start: Instant, duration: KotlinDuration) = Meeting(start, duration)
         }
     }
 
@@ -115,4 +118,32 @@ class DurationTests {
         assertEquals(result.start, Instant.parse("2023-06-20T14:00:00Z"))
         assertEquals(result.duration, 1.5.hours)
     }
+
+    data class JDTO(
+        val plain: JavaDuration = JavaDuration.ofHours(1),
+        val optPlain: JavaDuration? = JavaDuration.ofHours(1),
+        @field:JsonFormat(shape = STRING)
+        val shapeAnnotation: JavaDuration = JavaDuration.ofHours(1),
+        @field:JsonFormat(shape = STRING)
+        val optShapeAnnotation: JavaDuration? = JavaDuration.ofHours(1),
+    )
+
+    data class KDTO(
+        val plain: KotlinDuration = 1.hours,
+        val optPlain: KotlinDuration? = 1.hours,
+        @field:JsonFormat(shape = STRING)
+        val shapeAnnotation: KotlinDuration = 1.hours,
+        @field:JsonFormat(shape = STRING)
+        val optShapeAnnotation: KotlinDuration? = 1.hours,
+    )
+
+    @Test
+    fun `should serialize Kotlin duration exactly as Java duration`() {
+        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+
+        val jdto = JDTO()
+        val kdto = KDTO()
+
+        assertEquals(mapper.writeValueAsString(jdto), mapper.writeValueAsString(kdto))
+    }
 }
\ No newline at end of file

From bc2a0b354694fa5a59ff095125a2fc12b909ceb5 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 30 Jul 2023 11:57:15 +0200
Subject: [PATCH 06/16] Remarks

---
 .../com/fasterxml/jackson/module/kotlin/test/DurationTests.kt   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 40c436df3..7b5fdcaba 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -146,4 +146,4 @@ class DurationTests {
 
         assertEquals(mapper.writeValueAsString(jdto), mapper.writeValueAsString(kdto))
     }
-}
\ No newline at end of file
+}

From 79d8e4ebc404015ae6047e4d84b79ace5480d266 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Thu, 3 Aug 2023 18:34:54 +0200
Subject: [PATCH 07/16] Add feature toggle for Duration parsing

---
 .../jackson/module/kotlin/Converters.kt       |  9 +++--
 .../kotlin/KotlinAnnotationIntrospector.kt    |  9 +++--
 .../module/kotlin/KotlinDeserializers.kt      |  8 ++--
 .../jackson/module/kotlin/KotlinFeature.kt    |  9 ++++-
 .../jackson/module/kotlin/KotlinModule.kt     | 20 ++++++++--
 .../module/kotlin/test/DurationTests.kt       | 37 +++++++++++--------
 6 files changed, 61 insertions(+), 31 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index 0d63c4519..b96b1c829 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -25,10 +25,11 @@ internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, Jav
     val delegatingSerializer: StdDelegatingSerializer by lazy { StdDelegatingSerializer(this) }
 }
 
-// this class is needed as workaround for deserialization
-// data classes with kotlin.time.Duration field which is a value class
-//
-// @see DurationTests.`should deserialize Kotlin duration inside data class`
+/**
+ * Currently it is not possible to deduce type of [kotlin.time.Duration] fields therefore explicit annotation is needed on fields in order to properly deserialize POJO.
+ *
+ * @see [com.fasterxml.jackson.module.kotlin.test.DurationTests]
+ */
 object JavaToKotlinDurationConverter : StdConverter<JavaDuration, KotlinDuration>() {
     override fun convert(value: JavaDuration) = KotlinDuration.parseIsoString(value.toString())
 }
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index 7dfb4f87a..3aaf1a773 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -31,6 +31,7 @@ internal class KotlinAnnotationIntrospector(
     private val nullToEmptyCollection: Boolean,
     private val nullToEmptyMap: Boolean,
     private val nullIsSameAsDefault: Boolean,
+    private val useJavaDurationConversion: Boolean,
 ) : NopAnnotationIntrospector() {
 
     // TODO: implement nullIsSameAsDefault flag, which represents when TRUE that if something has a default value, it can be passed a null to default it
@@ -75,7 +76,7 @@ internal class KotlinAnnotationIntrospector(
 
     private fun lookupKotlinTypeConverter(a: AnnotatedClass) = when {
         Sequence::class.java.isAssignableFrom(a.rawType) -> SequenceToIteratorConverter(a.type)
-        Duration::class.java.isAssignableFrom(a.rawType) -> KotlinToJavaDurationConverter
+        Duration::class.java.isAssignableFrom(a.rawType) -> KotlinToJavaDurationConverter.takeIf { useJavaDurationConversion }
         else -> null
     }
 
@@ -92,9 +93,9 @@ internal class KotlinAnnotationIntrospector(
         ?.let { cache.getValueClassBoxConverter(am.rawReturnType, it).delegatingSerializer }
 
     override fun findSerializer(am: Annotated): Any? = when ((am as? AnnotatedMethod)?.ktClass()) {
-        Duration::class -> KotlinToJavaDurationConverter.delegatingSerializer
-        else -> super.findSerializer(am)
-    }
+        Duration::class -> KotlinToJavaDurationConverter.delegatingSerializer.takeIf { useJavaDurationConversion }
+        else -> null
+    } ?: super.findSerializer(am)
 
     /**
      * Subclasses can be detected automatically for sealed classes, since all possible subclasses are known
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
index eb3c424ce..807dbaca8 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
@@ -89,11 +89,13 @@ object ULongDeserializer : StdDeserializer<ULong>(ULong::class.java) {
         )
 }
 
-internal class KotlinDeserializers : Deserializers.Base() {
+internal class KotlinDeserializers(
+    private val useJavaDurationConversion: Boolean,
+) : Deserializers.Base() {
     override fun findBeanDeserializer(
         type: JavaType,
         config: DeserializationConfig?,
-        beanDesc: BeanDescription?
+        beanDesc: BeanDescription?,
     ): JsonDeserializer<*>? {
         return when {
             type.isInterface && type.rawClass == Sequence::class.java -> SequenceDeserializer
@@ -102,7 +104,7 @@ internal class KotlinDeserializers : Deserializers.Base() {
             type.rawClass == UShort::class.java -> UShortDeserializer
             type.rawClass == UInt::class.java -> UIntDeserializer
             type.rawClass == ULong::class.java -> ULongDeserializer
-            type.rawClass == KotlinDuration::class.java -> DurationDeserializer
+            type.rawClass == KotlinDuration::class.java -> DurationDeserializer.takeIf { useJavaDurationConversion }
             else -> null
         }
     }
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
index b6143fccf..8990d33d2 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
@@ -58,7 +58,14 @@ enum class KotlinFeature(private val enabledByDefault: Boolean) {
      * In addition, the adjustment of behavior using get:JvmName is disabled.
      * Note also that this feature does not apply to setters.
      */
-    KotlinPropertyNameAsImplicitName(enabledByDefault = false);
+    KotlinPropertyNameAsImplicitName(enabledByDefault = false),
+
+    /**
+     * This feature represents whether to handle [kotlin.time.Duration] using [java.time.Duration] as conversion bridge.
+     *
+     * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule].
+     */
+    UseJavaDurationConversion(enabledByDefault = false);
 
     internal val bitSet: BitSet = (1 shl ordinal).toBitSet()
 
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
index 5d75a1ade..aad2b9667 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
@@ -8,6 +8,7 @@ import com.fasterxml.jackson.module.kotlin.KotlinFeature.NullToEmptyCollection
 import com.fasterxml.jackson.module.kotlin.KotlinFeature.NullToEmptyMap
 import com.fasterxml.jackson.module.kotlin.KotlinFeature.StrictNullChecks
 import com.fasterxml.jackson.module.kotlin.KotlinFeature.KotlinPropertyNameAsImplicitName
+import com.fasterxml.jackson.module.kotlin.KotlinFeature.UseJavaDurationConversion
 import com.fasterxml.jackson.module.kotlin.SingletonSupport.CANONICALIZE
 import com.fasterxml.jackson.module.kotlin.SingletonSupport.DISABLED
 import java.util.*
@@ -33,6 +34,8 @@ fun Class<*>.isKotlinClass(): Boolean {
  *                                      the default, collections which are typed to disallow null members
  *                                      (e.g. List<String>) may contain null values after deserialization.  Enabling it
  *                                      protects against this but has significant performance impact.
+ * @param   useJavaDurationConversion Default: false.  Whether to use [java.time.Duration] as a bridge for [kotlin.time.Duration].
+ *                                      This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule].
  */
 class KotlinModule @Deprecated(
     level = DeprecationLevel.WARNING,
@@ -55,7 +58,8 @@ class KotlinModule @Deprecated(
     val nullIsSameAsDefault: Boolean = false,
     val singletonSupport: SingletonSupport = DISABLED,
     val strictNullChecks: Boolean = false,
-    val useKotlinPropertyNameForGetter: Boolean = false
+    val useKotlinPropertyNameForGetter: Boolean = false,
+    private val useJavaDurationConversion: Boolean = false,
 ) : SimpleModule(KotlinModule::class.java.name, PackageVersion.VERSION) {
     init {
         if (!KotlinVersion.CURRENT.isAtLeast(1, 5)) {
@@ -105,7 +109,8 @@ class KotlinModule @Deprecated(
             else -> DISABLED
         },
         builder.isEnabled(StrictNullChecks),
-        builder.isEnabled(KotlinPropertyNameAsImplicitName)
+        builder.isEnabled(KotlinPropertyNameAsImplicitName),
+        builder.isEnabled(UseJavaDurationConversion),
     )
 
     companion object {
@@ -132,7 +137,14 @@ class KotlinModule @Deprecated(
             }
         }
 
-        context.insertAnnotationIntrospector(KotlinAnnotationIntrospector(context, cache, nullToEmptyCollection, nullToEmptyMap, nullIsSameAsDefault))
+        context.insertAnnotationIntrospector(KotlinAnnotationIntrospector(
+            context,
+            cache,
+            nullToEmptyCollection,
+            nullToEmptyMap,
+            nullIsSameAsDefault,
+            useJavaDurationConversion
+        ))
         context.appendAnnotationIntrospector(
             KotlinNamesAnnotationIntrospector(
                 this,
@@ -141,7 +153,7 @@ class KotlinModule @Deprecated(
                 useKotlinPropertyNameForGetter)
         )
 
-        context.addDeserializers(KotlinDeserializers())
+        context.addDeserializers(KotlinDeserializers(useJavaDurationConversion))
         context.addKeyDeserializers(KotlinKeyDeserializers)
         context.addSerializers(KotlinSerializers())
         context.addKeySerializers(KotlinKeySerializers())
diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 7b5fdcaba..1445288e6 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -3,27 +3,30 @@ package com.fasterxml.jackson.module.kotlin.test
 import com.fasterxml.jackson.annotation.JsonCreator
 import com.fasterxml.jackson.annotation.JsonFormat
 import com.fasterxml.jackson.annotation.JsonFormat.Shape.STRING
+import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
 import com.fasterxml.jackson.module.kotlin.JavaToKotlinDurationConverter
-import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.KotlinFeature.UseJavaDurationConversion
+import com.fasterxml.jackson.module.kotlin.KotlinModule
+import com.fasterxml.jackson.module.kotlin.kotlinModule
 import com.fasterxml.jackson.module.kotlin.readValue
 import org.junit.Test
 import java.time.Instant
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
-import kotlin.time.Duration as KotlinDuration
-import java.time.Duration as JavaDuration
 import kotlin.time.Duration.Companion.hours
+import java.time.Duration as JavaDuration
+import kotlin.time.Duration as KotlinDuration
 
 class DurationTests {
+    private val objectMapper = jacksonObjectMapper { enable(UseJavaDurationConversion) }
+
     @Test
     fun `should serialize Kotlin duration using Java time module`() {
-        val mapper = jacksonObjectMapper()
-            .registerModule(JavaTimeModule())
-            .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
+        val mapper = objectMapper.registerModule(JavaTimeModule()).disable(WRITE_DURATIONS_AS_TIMESTAMPS)
 
         val result = mapper.writeValueAsString(1.hours)
 
@@ -32,7 +35,7 @@ class DurationTests {
 
     @Test
     fun `should deserialize Kotlin duration`() {
-        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+        val mapper = objectMapper.registerModule(JavaTimeModule())
 
         val result = mapper.readValue<KotlinDuration>("\"PT1H\"")
 
@@ -41,7 +44,7 @@ class DurationTests {
 
     @Test
     fun `should serialize Kotlin duration inside list using Java time module`() {
-        val mapper = jacksonObjectMapper()
+        val mapper = objectMapper
             .registerModule(JavaTimeModule())
             .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
 
@@ -52,7 +55,7 @@ class DurationTests {
 
     @Test
     fun `should deserialize Kotlin duration inside list`() {
-        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+        val mapper = objectMapper.registerModule(JavaTimeModule())
 
         val result = mapper.readValue<List<KotlinDuration>>("""["PT1H","PT2H","PT3H"]""")
 
@@ -61,7 +64,7 @@ class DurationTests {
 
     @Test
     fun `should serialize Kotlin duration inside map using Java time module`() {
-        val mapper = jacksonObjectMapper()
+        val mapper = objectMapper
             .registerModule(JavaTimeModule())
             .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
 
@@ -76,7 +79,7 @@ class DurationTests {
 
     @Test
     fun `should deserialize Kotlin duration inside map`() {
-        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+        val mapper = objectMapper.registerModule(JavaTimeModule())
 
         val result = mapper.readValue<Map<String, KotlinDuration>>("""{"a":"PT1H","b":"PT2H","c":"PT3H"}""")
 
@@ -99,7 +102,7 @@ class DurationTests {
 
     @Test
     fun `should serialize Kotlin duration inside data class using Java time module`() {
-        val mapper = jacksonObjectMapper()
+        val mapper = objectMapper
             .registerModule(JavaTimeModule())
             .disable(WRITE_DATES_AS_TIMESTAMPS)
             .disable(WRITE_DURATIONS_AS_TIMESTAMPS)
@@ -111,7 +114,7 @@ class DurationTests {
 
     @Test
     fun `should deserialize Kotlin duration inside data class`() {
-        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+        val mapper = objectMapper.registerModule(JavaTimeModule())
 
         val result = mapper.readValue<Meeting>("""{"start":"2023-06-20T14:00:00Z","duration":"PT1H30M"}""")
 
@@ -139,11 +142,15 @@ class DurationTests {
 
     @Test
     fun `should serialize Kotlin duration exactly as Java duration`() {
-        val mapper = jacksonObjectMapper().registerModule(JavaTimeModule())
+        val mapper = objectMapper.registerModule(JavaTimeModule())
 
         val jdto = JDTO()
         val kdto = KDTO()
 
         assertEquals(mapper.writeValueAsString(jdto), mapper.writeValueAsString(kdto))
     }
-}
+
+    private fun jacksonObjectMapper(
+        configuration: KotlinModule.Builder.() -> Unit,
+    ) = ObjectMapper().registerModule(kotlinModule(configuration))
+}
\ No newline at end of file

From b56e13977a3ef07cc623cf2cdade72f943c42886 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sat, 5 Aug 2023 07:49:51 +0200
Subject: [PATCH 08/16] Add doc note about current limitations

Kotlin Duration is value class and as Jackson has limited support of such cases it falls under few limits:
* data classes with Duration needs to have explicit creator method
* Duration fields has to be annotated with explicit `@JsonDeserializer` annotation

See `DurationTests` for details.
---
 .../com/fasterxml/jackson/module/kotlin/KotlinFeature.kt       | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
index 8990d33d2..09656aa55 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
@@ -63,7 +63,8 @@ enum class KotlinFeature(private val enabledByDefault: Boolean) {
     /**
      * This feature represents whether to handle [kotlin.time.Duration] using [java.time.Duration] as conversion bridge.
      *
-     * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule].
+     * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule] for serialization.
+     * For deserialization explicit creator method and annotation on Duration is needed.
      */
     UseJavaDurationConversion(enabledByDefault = false);
 

From 9709b83ebbc08ebbe39ad0931033b63de91bbe66 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sat, 5 Aug 2023 08:05:10 +0200
Subject: [PATCH 09/16] Remarks

---
 .../module/kotlin/KotlinAnnotationIntrospector.kt      | 10 +++++-----
 .../fasterxml/jackson/module/kotlin/KotlinModule.kt    |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index 3aaf1a773..e225f6adc 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -69,14 +69,14 @@ internal class KotlinAnnotationIntrospector(
 
     override fun findSerializationConverter(a: Annotated): Converter<*, *>? = when (a) {
         // Find a converter to handle the case where the getter returns an unboxed value from the value class.
-        is AnnotatedMethod -> a.ktClass()?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
+        is AnnotatedMethod -> a.findValueClassReturnType()?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
         is AnnotatedClass -> lookupKotlinTypeConverter(a)
         else -> null
     }
 
     private fun lookupKotlinTypeConverter(a: AnnotatedClass) = when {
         Sequence::class.java.isAssignableFrom(a.rawType) -> SequenceToIteratorConverter(a.type)
-        Duration::class.java.isAssignableFrom(a.rawType) -> KotlinToJavaDurationConverter.takeIf { useJavaDurationConversion }
+        Duration::class.java == a.rawType -> KotlinToJavaDurationConverter.takeIf { useJavaDurationConversion }
         else -> null
     }
 
@@ -88,11 +88,11 @@ internal class KotlinAnnotationIntrospector(
     // Perform proper serialization even if the value wrapped by the value class is null.
     // If value is a non-null object type, it must not be reboxing.
     override fun findNullSerializer(am: Annotated): JsonSerializer<*>? = (am as? AnnotatedMethod)
-        ?.ktClass()
+        ?.findValueClassReturnType()
         ?.takeIf { it.requireRebox() }
         ?.let { cache.getValueClassBoxConverter(am.rawReturnType, it).delegatingSerializer }
 
-    override fun findSerializer(am: Annotated): Any? = when ((am as? AnnotatedMethod)?.ktClass()) {
+    override fun findSerializer(am: Annotated): Any? = when ((am as? AnnotatedMethod)?.findValueClassReturnType()) {
         Duration::class -> KotlinToJavaDurationConverter.delegatingSerializer.takeIf { useJavaDurationConversion }
         else -> null
     } ?: super.findSerializer(am)
@@ -181,7 +181,7 @@ internal class KotlinAnnotationIntrospector(
         return requiredAnnotationOrNullability(byAnnotation, byNullability)
     }
 
-    private fun AnnotatedMethod.ktClass() = cache.findValueClassReturnType(this)
+    private fun AnnotatedMethod.findValueClassReturnType() = cache.findValueClassReturnType(this)
 
     private fun KFunction<*>.isConstructorParameterRequired(index: Int): Boolean {
         return isParameterRequired(index)
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
index aad2b9667..f3bd57fb6 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt
@@ -59,7 +59,7 @@ class KotlinModule @Deprecated(
     val singletonSupport: SingletonSupport = DISABLED,
     val strictNullChecks: Boolean = false,
     val useKotlinPropertyNameForGetter: Boolean = false,
-    private val useJavaDurationConversion: Boolean = false,
+    val useJavaDurationConversion: Boolean = false,
 ) : SimpleModule(KotlinModule::class.java.name, PackageVersion.VERSION) {
     init {
         if (!KotlinVersion.CURRENT.isAtLeast(1, 5)) {

From 7161b2b1da86bbcbcf504d22ffb804a26574fd8c Mon Sep 17 00:00:00 2001
From: wrongwrong <boranti1995@gmail.com>
Date: Sun, 6 Aug 2023 14:44:10 +0900
Subject: [PATCH 10/16] Fixing converter usage

---
 .../jackson/module/kotlin/Converters.kt       |  5 +++--
 .../kotlin/KotlinAnnotationIntrospector.kt    | 22 +++++++++++++++++++
 .../module/kotlin/test/DurationTests.kt       |  5 +----
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index b96b1c829..150fbb8d7 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -6,6 +6,7 @@ import com.fasterxml.jackson.databind.type.TypeFactory
 import com.fasterxml.jackson.databind.util.StdConverter
 import kotlin.reflect.KClass
 import kotlin.time.toJavaDuration
+import kotlin.time.toKotlinDuration
 import java.time.Duration as JavaDuration
 import kotlin.time.Duration as KotlinDuration
 
@@ -30,8 +31,8 @@ internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, Jav
  *
  * @see [com.fasterxml.jackson.module.kotlin.test.DurationTests]
  */
-object JavaToKotlinDurationConverter : StdConverter<JavaDuration, KotlinDuration>() {
-    override fun convert(value: JavaDuration) = KotlinDuration.parseIsoString(value.toString())
+internal object JavaToKotlinDurationConverter : StdConverter<JavaDuration, KotlinDuration>() {
+    override fun convert(value: JavaDuration) = value.toKotlinDuration()
 }
 
 // S is nullable because value corresponds to a nullable value class
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index e225f6adc..48e237920 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -13,6 +13,7 @@ import java.lang.reflect.AccessibleObject
 import java.lang.reflect.Constructor
 import java.lang.reflect.Field
 import java.lang.reflect.Method
+import java.lang.reflect.Modifier
 import kotlin.reflect.KClass
 import kotlin.reflect.KFunction
 import kotlin.reflect.KMutableProperty1
@@ -21,6 +22,7 @@ import kotlin.reflect.KType
 import kotlin.reflect.full.createType
 import kotlin.reflect.full.declaredMemberProperties
 import kotlin.reflect.full.memberProperties
+import kotlin.reflect.full.valueParameters
 import kotlin.reflect.jvm.*
 import kotlin.time.Duration
 
@@ -97,6 +99,26 @@ internal class KotlinAnnotationIntrospector(
         else -> null
     } ?: super.findSerializer(am)
 
+    override fun findDeserializationConverter(a: Annotated): Any? {
+        if (!useJavaDurationConversion) return null
+
+        return (a as? AnnotatedParameter)?.let { param ->
+            @Suppress("UNCHECKED_CAST")
+            val function: KFunction<*> = when (val owner = param.owner.member) {
+                is Constructor<*> -> cache.kotlinFromJava(owner as Constructor<Any>)
+                is Method -> cache.kotlinFromJava(owner)
+                else -> null
+            } ?: return@let null
+            val valueParameter = function.valueParameters[a.index]
+
+            if (valueParameter.type.classifier == Duration::class) {
+                JavaToKotlinDurationConverter
+            } else {
+                null
+            }
+        }
+    }
+
     /**
      * Subclasses can be detected automatically for sealed classes, since all possible subclasses are known
      * at compile-time to Kotlin. This makes [com.fasterxml.jackson.annotation.JsonSubTypes] redundant.
diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 1445288e6..8e196ab45 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -6,9 +6,7 @@ import com.fasterxml.jackson.annotation.JsonFormat.Shape.STRING
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS
 import com.fasterxml.jackson.databind.SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS
-import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
-import com.fasterxml.jackson.module.kotlin.JavaToKotlinDurationConverter
 import com.fasterxml.jackson.module.kotlin.KotlinFeature.UseJavaDurationConversion
 import com.fasterxml.jackson.module.kotlin.KotlinModule
 import com.fasterxml.jackson.module.kotlin.kotlinModule
@@ -90,7 +88,6 @@ class DurationTests {
 
     data class Meeting(
         val start: Instant,
-        @get:JsonDeserialize(converter = JavaToKotlinDurationConverter::class)
         val duration: KotlinDuration,
     ) {
         companion object {
@@ -153,4 +150,4 @@ class DurationTests {
     private fun jacksonObjectMapper(
         configuration: KotlinModule.Builder.() -> Unit,
     ) = ObjectMapper().registerModule(kotlinModule(configuration))
-}
\ No newline at end of file
+}

From a0151d422267109a246c95c18242633b235c3ae7 Mon Sep 17 00:00:00 2001
From: wrongwrong <boranti1995@gmail.com>
Date: Sun, 6 Aug 2023 14:53:15 +0900
Subject: [PATCH 11/16] Modified to use DelegatingDeserializer

---
 .../com/fasterxml/jackson/module/kotlin/Converters.kt  |  5 +++++
 .../jackson/module/kotlin/KotlinDeserializers.kt       | 10 ++--------
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index 150fbb8d7..b0063d262 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -1,6 +1,7 @@
 package com.fasterxml.jackson.module.kotlin
 
 import com.fasterxml.jackson.databind.JavaType
+import com.fasterxml.jackson.databind.deser.std.StdDelegatingDeserializer
 import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
 import com.fasterxml.jackson.databind.type.TypeFactory
 import com.fasterxml.jackson.databind.util.StdConverter
@@ -33,6 +34,10 @@ internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, Jav
  */
 internal object JavaToKotlinDurationConverter : StdConverter<JavaDuration, KotlinDuration>() {
     override fun convert(value: JavaDuration) = value.toKotlinDuration()
+
+    val delegatingDeserializer: StdDelegatingDeserializer<KotlinDuration> by lazy {
+        StdDelegatingDeserializer(this)
+    }
 }
 
 // S is nullable because value corresponds to a nullable value class
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
index 807dbaca8..0a927c9a0 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinDeserializers.kt
@@ -10,8 +10,6 @@ import com.fasterxml.jackson.databind.JavaType
 import com.fasterxml.jackson.databind.JsonDeserializer
 import com.fasterxml.jackson.databind.deser.Deserializers
 import com.fasterxml.jackson.databind.deser.std.StdDeserializer
-import kotlin.time.toKotlinDuration
-import java.time.Duration as JavaDuration
 import kotlin.time.Duration as KotlinDuration
 
 object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java) {
@@ -20,11 +18,6 @@ object SequenceDeserializer : StdDeserializer<Sequence<*>>(Sequence::class.java)
     }
 }
 
-internal object DurationDeserializer : StdDeserializer<KotlinDuration>(KotlinDuration::class.java) {
-    override fun deserialize(p: JsonParser, ctxt: DeserializationContext) = ctxt
-        .readValue(p, JavaDuration::class.java)?.toKotlinDuration()
-}
-
 object RegexDeserializer : StdDeserializer<Regex>(Regex::class.java) {
     override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Regex {
         val node = ctxt.readTree(p)
@@ -104,7 +97,8 @@ internal class KotlinDeserializers(
             type.rawClass == UShort::class.java -> UShortDeserializer
             type.rawClass == UInt::class.java -> UIntDeserializer
             type.rawClass == ULong::class.java -> ULongDeserializer
-            type.rawClass == KotlinDuration::class.java -> DurationDeserializer.takeIf { useJavaDurationConversion }
+            type.rawClass == KotlinDuration::class.java ->
+                JavaToKotlinDurationConverter.takeIf { useJavaDurationConversion }?.delegatingDeserializer
             else -> null
         }
     }

From bdc58b44a497d6b2d743a2eb12cf9d9a847292a2 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 6 Aug 2023 08:53:52 +0200
Subject: [PATCH 12/16] Add test cases involving mixins

---
 .../module/kotlin/test/DurationTests.kt       | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 8e196ab45..0fa4e2929 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -91,12 +91,18 @@ class DurationTests {
         val duration: KotlinDuration,
     ) {
         companion object {
+            @Suppress("unused")
             @JvmStatic
             @JsonCreator
             fun create(start: Instant, duration: KotlinDuration) = Meeting(start, duration)
         }
     }
 
+    abstract class MeetingMixin(
+        @Suppress("unused") @field:JsonFormat(shape = STRING)
+        val duration: KotlinDuration,
+    )
+
     @Test
     fun `should serialize Kotlin duration inside data class using Java time module`() {
         val mapper = objectMapper
@@ -119,6 +125,30 @@ class DurationTests {
         assertEquals(result.duration, 1.5.hours)
     }
 
+    @Test
+    fun `should deserialize Kotlin duration inside data class using mixin`() {
+        val mapper = objectMapper
+            .registerModule(JavaTimeModule())
+            .addMixIn(Meeting::class.java, MeetingMixin::class.java)
+
+        val meeting = mapper.readValue<Meeting>("""{"start":"2023-06-20T14:00:00Z","duration":"PT1H30M"}""")
+
+        assertEquals(Instant.parse("2023-06-20T14:00:00Z"), meeting.start)
+        assertEquals(1.5.hours, meeting.duration)
+    }
+
+    @Test
+    fun `should serialize Kotlin duration inside data class using Java time module and mixin`() {
+        val mapper = objectMapper
+            .registerModule(JavaTimeModule())
+            .disable(WRITE_DATES_AS_TIMESTAMPS)
+            .addMixIn(Meeting::class.java, MeetingMixin::class.java)
+
+        val result = mapper.writeValueAsString(Meeting(Instant.parse("2023-06-20T14:00:00Z"), 1.5.hours))
+
+        assertEquals("""{"start":"2023-06-20T14:00:00Z","duration":"PT1H30M"}""", result)
+    }
+
     data class JDTO(
         val plain: JavaDuration = JavaDuration.ofHours(1),
         val optPlain: JavaDuration? = JavaDuration.ofHours(1),

From 4fba300d5a0199079d9d12a60306e8806917441f Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 6 Aug 2023 09:03:42 +0200
Subject: [PATCH 13/16] Update feature java doc

---
 .../com/fasterxml/jackson/module/kotlin/KotlinFeature.kt      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
index 09656aa55..bc6bb9d79 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
@@ -63,8 +63,8 @@ enum class KotlinFeature(private val enabledByDefault: Boolean) {
     /**
      * This feature represents whether to handle [kotlin.time.Duration] using [java.time.Duration] as conversion bridge.
      *
-     * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule] for serialization.
-     * For deserialization explicit creator method and annotation on Duration is needed.
+     * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule].
+     * `@JsonFormat` annotations need to be declared either on getter using `@get:JsonFormat` or field using `@field:JsonFormat`.
      */
     UseJavaDurationConversion(enabledByDefault = false);
 

From e650766b260848797545fe2dfbce5dd3fde021a1 Mon Sep 17 00:00:00 2001
From: wrongwrong <boranti1995@gmail.com>
Date: Sun, 6 Aug 2023 16:14:57 +0900
Subject: [PATCH 14/16] Fixed conversion to be done by converter only

---
 .../jackson/module/kotlin/Converters.kt         |  8 ++++++--
 .../kotlin/KotlinAnnotationIntrospector.kt      | 17 ++++++++++-------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
index b0063d262..c27f82c69 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt
@@ -21,10 +21,14 @@ internal class SequenceToIteratorConverter(private val input: JavaType) : StdCon
         ?: typeFactory.constructType(Iterator::class.java)
 }
 
+internal object KotlinDurationValueToJavaDurationConverter : StdConverter<Long, JavaDuration>() {
+    private val boxConverter by lazy { ValueClassBoxConverter(Long::class.java, KotlinDuration::class) }
+
+    override fun convert(value: Long): JavaDuration = KotlinToJavaDurationConverter.convert(boxConverter.convert(value))
+}
+
 internal object KotlinToJavaDurationConverter : StdConverter<KotlinDuration, JavaDuration>() {
     override fun convert(value: KotlinDuration) = value.toJavaDuration()
-
-    val delegatingSerializer: StdDelegatingSerializer by lazy { StdDelegatingSerializer(this) }
 }
 
 /**
diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
index 48e237920..a06bd0142 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinAnnotationIntrospector.kt
@@ -13,7 +13,6 @@ import java.lang.reflect.AccessibleObject
 import java.lang.reflect.Constructor
 import java.lang.reflect.Field
 import java.lang.reflect.Method
-import java.lang.reflect.Modifier
 import kotlin.reflect.KClass
 import kotlin.reflect.KFunction
 import kotlin.reflect.KMutableProperty1
@@ -71,7 +70,16 @@ internal class KotlinAnnotationIntrospector(
 
     override fun findSerializationConverter(a: Annotated): Converter<*, *>? = when (a) {
         // Find a converter to handle the case where the getter returns an unboxed value from the value class.
-        is AnnotatedMethod -> a.findValueClassReturnType()?.let { cache.getValueClassBoxConverter(a.rawReturnType, it) }
+        is AnnotatedMethod -> a.findValueClassReturnType()?.let {
+            if (useJavaDurationConversion && it == Duration::class) {
+                if (a.rawReturnType == Duration::class.java)
+                    KotlinToJavaDurationConverter
+                else
+                    KotlinDurationValueToJavaDurationConverter
+            } else {
+                cache.getValueClassBoxConverter(a.rawReturnType, it)
+            }
+        }
         is AnnotatedClass -> lookupKotlinTypeConverter(a)
         else -> null
     }
@@ -94,11 +102,6 @@ internal class KotlinAnnotationIntrospector(
         ?.takeIf { it.requireRebox() }
         ?.let { cache.getValueClassBoxConverter(am.rawReturnType, it).delegatingSerializer }
 
-    override fun findSerializer(am: Annotated): Any? = when ((am as? AnnotatedMethod)?.findValueClassReturnType()) {
-        Duration::class -> KotlinToJavaDurationConverter.delegatingSerializer.takeIf { useJavaDurationConversion }
-        else -> null
-    } ?: super.findSerializer(am)
-
     override fun findDeserializationConverter(a: Annotated): Any? {
         if (!useJavaDurationConversion) return null
 

From f2e51b4f3aaab41df84c919ee9937fe69117dee8 Mon Sep 17 00:00:00 2001
From: Krzysztof Kurczewski <krzysiek.kurczewski@gmail.com>
Date: Sun, 6 Aug 2023 09:59:20 +0200
Subject: [PATCH 15/16] Add test for deserializing correct units from format
 annotation

---
 .../module/kotlin/test/DurationTests.kt       | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
index 0fa4e2929..75db96297 100644
--- a/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
+++ b/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/DurationTests.kt
@@ -16,6 +16,7 @@ import java.time.Instant
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
 import kotlin.time.Duration.Companion.hours
+import kotlin.time.Duration.Companion.seconds
 import java.time.Duration as JavaDuration
 import kotlin.time.Duration as KotlinDuration
 
@@ -177,6 +178,31 @@ class DurationTests {
         assertEquals(mapper.writeValueAsString(jdto), mapper.writeValueAsString(kdto))
     }
 
+    data class DurationWithFormattedUnits(
+        @field:JsonFormat(pattern = "HOURS") val formatted: KotlinDuration,
+        val default: KotlinDuration,
+    ) {
+        companion object {
+            @Suppress("unused")
+            @JvmStatic
+            @JsonCreator
+            fun create(
+                formatted: KotlinDuration,
+                default: KotlinDuration,
+            ) = DurationWithFormattedUnits(formatted, default)
+        }
+    }
+
+    @Test
+    fun `should deserialize using custom units specified by format annotation`() {
+        val mapper = objectMapper.registerModule(JavaTimeModule())
+
+        val actual = mapper.readValue<DurationWithFormattedUnits>("""{"formatted":1,"default":1}""")
+
+        assertEquals(1.hours, actual.formatted)
+        assertEquals(1.seconds, actual.default)
+    }
+
     private fun jacksonObjectMapper(
         configuration: KotlinModule.Builder.() -> Unit,
     ) = ObjectMapper().registerModule(kotlinModule(configuration))

From 73bf6824825a88b9255c890d3ac4f13590c169ee Mon Sep 17 00:00:00 2001
From: kkurczewski <kkurczewski@users.noreply.github.com>
Date: Sun, 6 Aug 2023 13:39:40 +0200
Subject: [PATCH 16/16] Add related issue reference in docs

Co-authored-by: wrongwrong <k163377@users.noreply.github.com>
---
 .../kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt  | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
index bc6bb9d79..93dba381f 100644
--- a/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
+++ b/src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt
@@ -65,6 +65,7 @@ enum class KotlinFeature(private val enabledByDefault: Boolean) {
      *
      * This allows use Kotlin Duration type with [com.fasterxml.jackson.datatype.jsr310.JavaTimeModule].
      * `@JsonFormat` annotations need to be declared either on getter using `@get:JsonFormat` or field using `@field:JsonFormat`.
+     * See [jackson-module-kotlin#651] for details.
      */
     UseJavaDurationConversion(enabledByDefault = false);