Embedded entities can not be constructed when they use Kotlin `val` properties

[koenpunt]

To retrieve results indexed by a specific column (relation_id), we use "pair" classes. For example;

// Repository method
@Query(
    """
        SELECT o.id AS relation_id, c.* FROM customer_details c
        JOIN orders o ON o.customer_details_id = c.id
        WHERE o.id IN (:ids)
    """
)
suspend fun findAllByOrderIdIn(ids: Iterable<UUID>): List<CustomerDetailsPair>

// ...

// The virtual pair entity
data class CustomerDetailsPair(
    override val relationId: UUID,
    @Embedded.Empty
    override val entity: CustomerDetails,
)

// The CustomerDetails entity
@Table(name = "customer_details")
class CustomerDetails(
    val name: String,
    var email: String?,
)

But this results in the following exception being thrown:

Cannot set property name because no setter, no wither and it's not part of the persistence constructor public oopen.timemachine.entities.CustomerDetails(java.lang.String,java.lang.String)

When changing the name property to a var, no error is thrown. The entity as a standalone entity, so not embedded, can be constructed without changing the property to a var.

[mp911de]

Care to include the full stack trace?

[koenpunt]

Here you go:

Caused by: java.lang.IllegalStateException: Cannot set property name because no setter, no wither and it's not part of the persistence constructor public oopen.timemachine.entities.CustomerDetails(java.lang.String,java.lang.String,com.google.i18n.phonenumbers.Phonenumber$PhoneNumber,java.util.UUID,boolean,java.util.UUID,boolean)
	at org.springframework.data.mapping.model.InstantiationAwarePropertyAccessor.setProperty(InstantiationAwarePropertyAccessor.java:93)
	at org.springframework.data.mapping.model.ConvertingPropertyAccessor.setProperty(ConvertingPropertyAccessor.java:60)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.readProperties(MappingRelationalConverter.java:556)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.populateProperties(MappingRelationalConverter.java:523)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.read(MappingRelationalConverter.java:457)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.readEmbedded(MappingRelationalConverter.java:566)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter$2.getPropertyValue(MappingRelationalConverter.java:490)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter$2.getPropertyValue(MappingRelationalConverter.java:475)
	at org.springframework.data.mapping.model.PersistentEntityParameterValueProvider.getParameterValue(PersistentEntityParameterValueProvider.java:71)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter$ConvertingParameterValueProvider.getParameterValue(MappingRelationalConverter.java:1161)
	at org.springframework.data.mapping.model.SpELExpressionParameterValueProvider.getParameterValue(SpELExpressionParameterValueProvider.java:49)
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.extractInvocationArguments(ClassGeneratingEntityInstantiator.java:301)
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator$EntityInstantiatorAdapter.createInstance(ClassGeneratingEntityInstantiator.java:273)
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:98)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.read(MappingRelationalConverter.java:454)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.readAggregate(MappingRelationalConverter.java:348)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.readAggregate(MappingRelationalConverter.java:311)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.read(MappingRelationalConverter.java:298)
	at org.springframework.data.relational.core.conversion.MappingRelationalConverter.read(MappingRelationalConverter.java:294)
	at org.springframework.data.r2dbc.core.R2dbcEntityTemplate.lambda$getRowsFetchSpec$13(R2dbcEntityTemplate.java:795)
	at io.r2dbc.proxy.callback.ResultCallbackHandler.lambda$invoke$0(ResultCallbackHandler.java:92)
	at io.r2dbc.proxy.callback.ResultCallbackHandler.lambda$invoke$0(ResultCallbackHandler.java:92)
	at io.r2dbc.postgresql.PostgresqlResult.lambda$map$2(PostgresqlResult.java:129)
	at reactor.core.publisher.ContextPropagation.lambda$contextRestoreForHandle$2(ContextPropagation.java:173)
	at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:113)
	at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onNext(MonoFlatMapMany.java:250)
	at reactor.core.publisher.FluxHandleFuseable$HandleFuseableSubscriber.onNext(FluxHandleFuseable.java:194)
	at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:337)
	at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onNext(FluxContextWrite.java:107)
	at reactor.core.publisher.FluxPeekFuseable$PeekConditionalSubscriber.onNext(FluxPeekFuseable.java:854)
	at reactor.core.publisher.FluxPeekFuseable$PeekConditionalSubscriber.onNext(FluxPeekFuseable.java:854)
	at io.r2dbc.postgresql.util.FluxDiscardOnCancel$FluxDiscardOnCancelSubscriber.onNext(FluxDiscardOnCancel.java:91)
	at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onNext(FluxDoFinally.java:113)
	at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:129)
	at reactor.core.publisher.FluxCreate$BufferAsyncSink.drain(FluxCreate.java:880)
	at reactor.core.publisher.FluxCreate$BufferAsyncSink.next(FluxCreate.java:805)
	at reactor.core.publisher.FluxCreate$SerializedFluxSink.next(FluxCreate.java:163)
	at io.r2dbc.postgresql.client.ReactorNettyClient$Conversation.emit(ReactorNettyClient.java:684)
	at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.emit(ReactorNettyClient.java:936)
	at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.onNext(ReactorNettyClient.java:810)
	at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.onNext(ReactorNettyClient.java:716)
	at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:129)
	at reactor.core.publisher.FluxPeekFuseable$PeekConditionalSubscriber.onNext(FluxPeekFuseable.java:854)
	at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onNext(FluxMap.java:224)
	at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onNext(FluxMap.java:224)
	at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:294)
	at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:403)
	at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:426)
	at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:114)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:333)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:454)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:290)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:1623)

[koenpunt]

Just found out that it doesn't throw an exception when making the CustomerDetails entity a data class, but we're not sure what side effects that could have.

[mp911de]

CustomerDetailsPair uses overridden properties. That's not supported as Kotlin creates two properties without being able to set reliably both.

Without the override keyword, I'm not able to reproduce the issue.

[koenpunt]

For completeness, the pair class implements an interface, and doesn't inherit from a class;

data class CustomerDetailsPair(
    override val relationId: UUID,
    @Embedded.Empty
    override val entity: CustomerDetails,
) : EntityPair<UUID, CustomerDetails>

interface EntityPair<F, S> {
    val relationId: F
    val entity: S
}

But also when I remove the interface and the override from the properties of the pair the exception is thrown.

[koenpunt]

@mp911de I noticed you assigned yourself; do you maybe have an update regarding this?