Problem with kotlin field with fixed value

[ederfmatos]

I have the following data class in kotlin, where the "type" attribute always has the fixed value "BILLET", this is because the interface that my class implements asks for this attribute.

data class BilletTransaction(
    override val id: String,
    override val name: TransactionName,
    override val createdAt: ZonedDateTime,
    override val value: BigDecimal,
    val dueDate: LocalDate,
) : Transaction {
    override val type: TransactionType = TransactionType.BILLET
}

I have a record in the mongo database with this information, but when trying to read it I get the following error:

java.lang.UnsupportedOperationException: No accessor to set property private final transient <PACKAGE>.TransactionType <PACKAGE>.BilletTransaction.type
	at <PACKAGE>.BilletTransaction_Accessor_wa9qij.setProperty(Unknown Source)
	at org.springframework.data.mapping.model.InstantiationAwarePropertyAccessor.setProperty(InstantiationAwarePropertyAccessor.java:81)
	at org.springframework.data.mapping.model.ConvertingPropertyAccessor.setProperty(ConvertingPropertyAccessor.java:60)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readProperties(MappingMongoConverter.java:606)

I noticed that in the class "InstantiationAwarePropertyAccessor" there is a method that tries to use a possible "setter" to configure the value, but it is not possible and the error occurs

Is it possible to get around this error?

[ederfmatos]

Using Transient annotation this problem is fixed, but the value of field is not saved in the database. In this case, the field is no writable field, is read only

[mp911de]

The root of this is that we should refrain from reading immutable properties in the first place. Generally speaking, if the field in your domain model is set to a fixed value, it doesn't make sense to write it to the database.

As MappingMongoConverter is attempting to read a value for an immutable property, we should rather attempt to filter out such properties from being read.