Spring [Need to reopen] List serialization fails with Incompatible types when generics are used.

Affects: >=2.5.6, fails for latest 3.0 too of spring boot

---

Issue:

After upgrading spring boot to 2.5.14, serialization of a Restcontroller method with generic return type is failing when list is returned, works fine when return type has non list class.

How to reproduce

Repo link - https://github.com/alpeshvas/spring-list-deserialization-issue

package com.example.springlistdeserializationissue.controllers

import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController
import utils.APIResponse

data class AMTemp(val name: String)

@RestController
@RequestMapping("/test")
class TestController {
    @GetMapping("/test-json-works")
    suspend fun testJson(): APIResponse<AMTemp> {
        return APIResponse.Success(AMTemp("test"))
    }

    @GetMapping("/test-json-fail")
    suspend fun testJsonFail(): APIResponse<List<String>> {
        return APIResponse.Success(listOf("test"))
    }
}

Data models for APIResponse

package utils

import com.fasterxml.jackson.annotation.JsonValue
import org.springframework.http.HttpStatus
import org.springframework.http.ResponseEntity

sealed class APIResponse<T>(httpStatus: HttpStatus) : ResponseEntity<APIResponse<T>>(httpStatus) {

    class Success<T>(
        private val response: T,
        val status: HttpStatus = HttpStatus.OK
    ) : APIResponse<T>(status) {
        override fun getBody(): APIResponse<T> = this
        @JsonValue fun value() = response
    }

    class Error<T>(
        private val httpStatus: HttpStatus,
        private val errorCode: String,
        private val message: String
    ) : APIResponse<T>(httpStatus) {
        override fun getBody() = this
        @JsonValue fun value() = mapOf(
            "errorCode" to errorCode,
            "message" to message
        )
    }
}

Error message

Short:

Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Incompatible types: declared root type ([collection type; class java.util.List, contains [simple type, class java.lang.String]]) vs `utils.APIResponse$Success`
    at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1276) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.SerializerProvider._reportIncompatibleRootType(SerializerProvider.java:1369) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:381) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1510) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:1006) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at org.springframework.http.codec.json.AbstractJackson2Encoder.encodeValue(AbstractJackson2Encoder.java:226) ~[spring-web-5.3.20.jar:5.3.20]

Original Stack Trace:

        at org.springframework.http.codec.json.AbstractJackson2Encoder.encodeValue(AbstractJackson2Encoder.java:230) ~[spring-web-5.3.20.jar:5.3.20]
        at org.springframework.http.codec.json.AbstractJackson2Encoder.lambda$encode$0(AbstractJackson2Encoder.java:150) ~[spring-web-5.3.20.jar:5.3.20]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:113) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoSingle$SingleSubscriber.doOnRequest(MonoSingle.java:103) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MonoInnerProducerBase.request(Operators.java:2731) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2194) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2068) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:115) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxFilter$FilterSubscriber.onNext(FluxFilter.java:113) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:172) ~[reactor-core-3.4.18.jar:3.4.18]
        at kotlinx.coroutines.reactor.MonoCoroutine.onCompleted(Mono.kt:101) ~[kotlinx-coroutines-reactor-1.5.2.jar:na]
        at kotlinx.coroutines.AbstractCoroutine.onCompletionInternal(AbstractCoroutine.kt:93) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.JobSupport.tryFinalizeSimpleState(JobSupport.kt:294) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.JobSupport.tryMakeCompleting(JobSupport.kt:856) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.JobSupport.makeCompletingOnce$kotlinx_coroutines_core(JobSupport.kt:828) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.AbstractCoroutine.resumeWith(AbstractCoroutine.kt:100) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) ~[kotlin-stdlib-1.6.21.jar:1.6.21-release-334(1.6.21)]
        at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:367) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
        at kotlinx.coroutines.reactor.MonoKt.monoInternal$lambda-2(Mono.kt:90) ~[kotlinx-coroutines-reactor-1.5.2.jar:na]
        at reactor.core.publisher.MonoCreate.subscribe(MonoCreate.java:58) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.complete(MonoIgnoreThen.java:292) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onNext(MonoIgnoreThen.java:187) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:151) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoZip$ZipCoordinator.signal(MonoZip.java:251) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoZip$ZipInner.onNext(MonoZip.java:336) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoZip$ZipInner.onSubscribe(MonoZip.java:325) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onSubscribe(MonoPeekTerminal.java:152) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:128) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:240) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onComplete(MonoFlatMap.java:181) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators.complete(Operators.java:137) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:120) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.innerNext(FluxConcatMap.java:282) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:863) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2194) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2068) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onSubscribe(MonoPeekTerminal.java:152) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:451) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:219) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:165) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:87) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
        at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:967) ~[reactor-netty-http-1.0.19.jar:1.0.19]
        at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:677) ~[reactor-netty-core-1.0.19.jar:1.0.19]
        at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:478) ~[reactor-netty-core-1.0.19.jar:1.0.19]
        at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:570) ~[reactor-netty-http-1.0.19.jar:1.0.19]
        at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93) ~[reactor-netty-core-1.0.19.jar:1.0.19]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:222) ~[reactor-netty-http-1.0.19.jar:1.0.19]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:327) ~[netty-codec-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:299) ~[netty-codec-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:487) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:385) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:995) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
        at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
        at java.base/java.lang.Thread.run(Thread.java:1589) ~[na:na]
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Incompatible types: declared root type ([collection type; class java.util.List, contains [simple type, class java.lang.String]]) vs `utils.APIResponse$Success`
    at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1276) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.SerializerProvider._reportIncompatibleRootType(SerializerProvider.java:1369) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:381) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1510) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:1006) ~[jackson-databind-2.12.6.1.jar:2.12.6.1]
    at org.springframework.http.codec.json.AbstractJackson2Encoder.encodeValue(AbstractJackson2Encoder.java:226) ~[spring-web-5.3.20.jar:5.3.20]
    at org.springframework.http.codec.json.AbstractJackson2Encoder.lambda$encode$0(AbstractJackson2Encoder.java:150) ~[spring-web-5.3.20.jar:5.3.20]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:113) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoSingle$SingleSubscriber.doOnRequest(MonoSingle.java:103) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MonoInnerProducerBase.request(Operators.java:2731) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2194) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2068) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoSingle$SingleSubscriber.onSubscribe(MonoSingle.java:115) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxFilter$FilterSubscriber.onNext(FluxFilter.java:113) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:172) ~[reactor-core-3.4.18.jar:3.4.18]
    at kotlinx.coroutines.reactor.MonoCoroutine.onCompleted(Mono.kt:101) ~[kotlinx-coroutines-reactor-1.5.2.jar:na]
    at kotlinx.coroutines.AbstractCoroutine.onCompletionInternal(AbstractCoroutine.kt:93) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.JobSupport.tryFinalizeSimpleState(JobSupport.kt:294) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.JobSupport.tryMakeCompleting(JobSupport.kt:856) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.JobSupport.makeCompletingOnce$kotlinx_coroutines_core(JobSupport.kt:828) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.AbstractCoroutine.resumeWith(AbstractCoroutine.kt:100) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) ~[kotlin-stdlib-1.6.21.jar:1.6.21-release-334(1.6.21)]
    at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:367) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126) ~[kotlinx-coroutines-core-jvm-1.5.2.jar:na]
    at kotlinx.coroutines.reactor.MonoKt.monoInternal$lambda-2(Mono.kt:90) ~[kotlinx-coroutines-reactor-1.5.2.jar:na]
    at reactor.core.publisher.MonoCreate.subscribe(MonoCreate.java:58) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.complete(MonoIgnoreThen.java:292) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onNext(MonoIgnoreThen.java:187) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:151) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoZip$ZipCoordinator.signal(MonoZip.java:251) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoZip$ZipInner.onNext(MonoZip.java:336) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoZip$ZipInner.onSubscribe(MonoZip.java:325) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onSubscribe(MonoPeekTerminal.java:152) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:128) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:240) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onComplete(MonoFlatMap.java:181) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators.complete(Operators.java:137) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:120) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.innerNext(FluxConcatMap.java:282) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:863) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2194) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2068) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onSubscribe(MonoPeekTerminal.java:152) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:451) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:219) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:165) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:87) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.Mono.subscribe(Mono.java:4400) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55) ~[reactor-core-3.4.18.jar:3.4.18]
    at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:967) ~[reactor-netty-http-1.0.19.jar:1.0.19]
    at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:677) ~[reactor-netty-core-1.0.19.jar:1.0.19]
    at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:478) ~[reactor-netty-core-1.0.19.jar:1.0.19]
    at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:570) ~[reactor-netty-http-1.0.19.jar:1.0.19]
    at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93) ~[reactor-netty-core-1.0.19.jar:1.0.19]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:222) ~[reactor-netty-http-1.0.19.jar:1.0.19]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:327) ~[netty-codec-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:299) ~[netty-codec-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:487) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:385) ~[netty-transport-classes-epoll-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:995) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.77.Final.jar:4.1.77.Final]
    at java.base/java.lang.Thread.run(Thread.java:1589) ~[na:na]
....
````



**Comment From: alpeshvas**

Tried to debug this and it looks like a bug, nestinglevel is not correctly set, and it seems like started happening since this - https://github.com/spring-projects/spring-framework/commit/0436dd04bff89670a0e307e7183220b04f97878a   @rstoyanchev 

**Comment From: alpeshvas**

@rstoyanchev can you have a look? Have provided reproducer too.

**Comment From: alpeshvas**

@rstoyanchev (not sure whom to tag) rebumping.

**Comment From: alpeshvas**

@sdeleuze tagging you since it looks like you're actively responding to spring serialization related issues. Can you help us get some attention to this issue. We are not able to upgrade to 2.6+ due to this. 

**Comment From: alpeshvas**

> @sdeleuze tagging you since it looks like you're actively responding to spring serialization related issues. Can you help us get some attention to this issue. We are not able to upgrade to 2.6+ due to this. 

@sdeleuze it's failing for all versions from 2.6.x to 3.0.x, have shared a reproducer repo as well in the description if you want to reproduce the issue.

**Comment From: alpeshvas**

@sdeleuze @rstoyanchev bumping up again :see_no_evil: 

**Comment From: sdeleuze**

I can indeed reproduce regardless Spring Boot version used, but I am not sure the issue is on Spring Boot side.

For example, this fails as well:
```kotlin
@GetMapping("/test-json-text")
fun testJsonText(): APIResponse<String> {
    return APIResponse.Success("test")
}

Could be that this kind of sealed class + com.fasterxml.jackson.annotation.JsonValue is not supported by Jackson (could be on purpose or a bug).

Could you please have another look and see if you can create a test where Jackson successfully serialize this kind of use case or point us where Spring does not properly provide the type information to Jackson?

Comment From: spring-projects-issues

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

Comment From: alpeshvas

Yup, you're right. That's also also failing. Failing cases: Case 1:

@GetMapping("/test-json-text")
fun testJsonText(): APIResponse<String> {
    return APIResponse.Success("test")
}

Case 2:

   @GetMapping("/test-json-fail")
    suspend fun testJsonFail(): APIResponse<List<String>> {
        return APIResponse.Success(listOf("test"))
    }

Success Case:

    @GetMapping("/test-json-success")
    suspend fun testJson(): APIResponse<AMTemp> {
        return APIResponse.Success(AMTemp("test"))
    }

Comment From: sdeleuze

Thanks for your feedback, please report this issue to https://github.com/FasterXML/jackson-module-kotlin, linking this one to allow Jackson team to have context and repros.

Comment From: alpeshvas

@sdeleuze it sorry for long period of silence here, so I have checked if this is due to jackson-kotlin but it's not, I have added more tests in that repo to see if that's the case, you can check it here

This works completely fine:

    @Test
    fun `jackson deserialization works fine`() {
        val writer = jacksonObjectMapper().writer().forType(jacksonTypeRef<APIResponse<List<AMSummaryData>>>())
        val response = APIResponse.Success(listOf(AMSummaryData(name = "test", value = "test", change = "test")))
        val value = writer.writeValueAsString(response)
        // json assert
        assertEquals("{\"headers\":{},\"body\":[{\"name\":\"test\",\"value\":\"test\",\"change\":\"test\"}],\"statusCode\":\"OK\",\"statusCodeValue\":200}", value)
    }

but in spring controller, it fails to deserialize it to json.

    @GetMapping("/test-json-list-summary")
    suspend fun testJsonFail(): APIResponse<List<AMSummaryData>> {
        return APIResponse.Success(listOf(AMSummaryData("test", "4", "5")))
    }

Accompanying controller tests

    @Test
    fun `test json fail`() {
        webTestClient.get().uri("/test/test-json-list-summary")
            .exchange()
            .expectStatus().isOk
            .expectBody()
    }

If you want to try it out - I have added tests here https://github.com/alpeshvas/spring-list-deserialization-issue/tree/main/src/test/kotlin/com/example/springlistdeserializationissue

Comment From: alpeshvas

Same tests works in 2.5.3, you can check the branch here - https://github.com/alpeshvas/spring-list-deserialization-issue/pull/1/files

Comment From: alpeshvas

It works fine in 2.5.5 too, starts failing from 2.5.6 as it's mentioned in the issue description.

Comment From: alpeshvas

jakcson deserialization works for all 2.x (post 2.5.6. too) so it doesn't seem like jackson issue.

Comment From: alpeshvas

@sdeleuze changing nesting levels fix the issue for me, that might give you some insights here - https://github.com/spring-projects/spring-framework/pull/32895/files

Comment From: alpeshvas

@sdeleuze I have fixed with a hack of checking generics level - please have a look, not sure if that's the right approach - https://github.com/spring-projects/spring-framework/pull/32895/commits/9e54426c1e396b973248a6d38fb83064ddbc9def

Comment From: alpeshvas

@sdeleuze bumping up.

Comment From: alpeshvas

@sdeleuze can we reopen this?

Comment From: alpeshvas

@spring-projects-issues (bot) open this.