Spring MongoDB Upsert Map Contents

Question

Currently I'm trying to, in an atomic way, since there will be multiple processes trying to access the same document, update or insert a document that contains multiple fields, one of which is a Map<Instant, Position>.

For this, I'm trying to use MongoTemplate, specifically the findAndModify() method which I've read provides the ACID properties I'm looking for. Given this, the query I implemented was the following:

slot.positions.forEach { position ->
    mongoTemplate.findAndModify(
        Query.query(Criteria.where("assetId").`is`(slot.assetId).and("startTime").`is`(slot.start)),
        Update().set("positions.${position.key}", position.value).setOnInsert("updatedAt", Instant.now()),
        FindAndModifyOptions.options().upsert(true),
        SlotDocument::class.java,
    )
}

The logic behind this was to try and upsert each position one at a time given that I do not know how to upsert the entire document all at once.

This attempt actually saves two positions successfully but then fails with the message:

org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [java.time.Instant] for value [2023-08-28T09:57:30]
...
Caused by: java.time.format.DateTimeParseException: Text '2023-08-28T09:57:30' could not be parsed at index 19

This could be related to another issue I identified while debugging which was ever since I changed to the MongoTemplate, my MappgingMongoConverter stopped transforming . into MIL as specified by the code below

@Configuration
class MongoConfig {

    /**
    * This was my new attempt when changing to MongoTemplate
    */
    @Bean
    fun mongoTemplate(mongoDatabaseFactory: MongoDatabaseFactory, mappingMongoConverter: MappingMongoConverter): MongoTemplate {
        mappingMongoConverter.setMapKeyDotReplacement("MIL")
        return MongoTemplate(mongoDatabaseFactory, mappingMongoConverter)
    }

    /**
     * Replaces dots in map keys that are to be stored in MongoDB
     * This was the initial and successful attempt when using MongoRepository
     */
    @Autowired
    fun setMapKeyDotReplacement(mappingMongoConverter: MappingMongoConverter) {
        mappingMongoConverter.setMapKeyDotReplacement("MIL")
    }
}

So in the end, to summarise, I cannot:

• Upsert my slot document in order to, keeping the Atomic property, update the document and the content of its map field;
• Replace the . in the keys (Instant) of the map which is causing problems with the data structure in MongoDB