Why spring data dynamodb are returning a list with null element instead a empty list?

Question

When I invoke a repository method that makes a key search in dynamo:

"{"TableName":"music","Key":{"artist":{"S":"Henrique"},"title":{"S":"Quinta_de_sol1"}},"ConsistentRead":false}"

this is aws output:

"{}"

And when i invoke another methos that makes a find using sortKey start with:

this is sent to aws:

"{"TableName":"music","ConsistentRead":true,"KeyConditions":{"artist":{"AttributeValueList":[{"S":"Djavan"}],"ComparisonOperator":"EQ"},"title":{"AttributeValueList":[{"S":"Tempo"}],"ComparisonOperator":"BEGINS_WITH"}},"ScanIndexForward":true}"

and this is the return:

"{"Count":0,"Items":[],"ScannedCount":0}"

Steps to Reproduce the Problem

Using a entity named Music

@DynamoDBTable(tableName = "music")
data class Music(

        @get:DynamoDBHashKey(attributeName = "artist")
        var artist: String? = null,

        @get:DynamoDBRangeKey(attributeName = "title")
        var title: String? = null,

        var genre: String? = null
) {

    @Id
    private var id: MusicId? = null
        get() = MusicId(artist, title)
}

@DynamoDBDocument
data class MusicId(

        @field:DynamoDBHashKey(attributeName = "artist")
        var artist: String? = null,

        @field:DynamoDBRangeKey(attributeName = "title")
        var title: String? = null
) : Serializable

And a repository

interface MusicRepository : CrudRepository<Music, MusicId> {

    fun findByArtistAndTitle(artist: String, title: String): List<Music>

    fun findByArtistAndTitleStartingWith(artista: String, sortKey: String): List<Music>
}

And when i invoke:

@PostConstruct
    fun init() {
        println(musicRepository.findByArtistAndTitleStartingWith("Djavan", "Eu te devoro").joinToString())
    }

Specifications

Lib: https://github.com/boostchicken/spring-data-dynamodb
Spring Data DynamoDB Version: 5.2.5
Spring Data Version: Doesn't used
Spring Boot Starter Web Version: 2.3.4.RELEASE
AWS SDK Version: 1.11.573
Java Version: 11
Platform Details: Windows

Someone know if is there a clean way to guarantee that the dynamo repo will never return a list that only accepts non null elements, with null elements?

smac2020 smac2020 · Accepted Answer · 2021-02-02T01:46:22

To write a Spring application that invokes Amazon DynamoDB, consider using the official Amazon DynamoDB Java V2 API and the enhanced client within a Spring project.

Map items in DynamoDB tables

If you are not familiar with the AWS SDK for Java V2, please refer to this Quick Start.

Why spring data dynamodb are returning a list with null element instead a empty list?

Steps to Reproduce the Problem

Specifications

1 Answers