I have a problem with an XML DTO. I was trying to assemble it in Spring Boot 3.3.5 and jackson-dataformat-xml v2.18.2. The issue here is that I have two lists that contain children with the same name in a DTO.
The DTO looks like this:

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import java.util.List;
import lombok.Builder;
import lombok.Getter;
import lombok.Setter;

@Builder
public class PlayerActivityDto {
    @JacksonXmlProperty(localName = "playerActivityId", isAttribute = true)
    private String brandId;

    @JacksonXmlProperty(localName = "player")
    private PlayerDto player;

    @JacksonXmlProperty(localName = "playerActivityDetail")
    private PlayerActivityDetailDto playerActivityDetail;

    @Setter
    @Getter
    @JacksonXmlProperty(localName = "summaryBalance")
    @JacksonXmlElementWrapper(localName = "startingBalanceList")
    private List<SummaryBalanceDto> startingBalanceList;

    @Getter
    @Setter
    @JacksonXmlProperty(localName = "summaryBalance")
    @JacksonXmlElementWrapper(localName = "endingBalanceList")
    private List<SummaryBalanceDto> endingBalanceList;

    @JacksonXmlProperty(localName = "playerMovement")
    @JacksonXmlElementWrapper(localName = "playerMovementList")
    private List<FundsMovementDto> playerMovementList;
}

The issue i have with is the two lists named endingBalanceList and startingBalanceList. AFAIK, @JacksonXmlProperty(localName = "summaryBalance") should name the children of lists endingBalanceList and startingBalanceList “summaryBalance” and should produce valid XML.

However, Jackson produces this exception:

Failed to evaluate Jackson serialization for type [class PlayerActivityDto]: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Conflicting getter definitions for property “summaryBalance”: PlayerActivityDto#getStartingBalanceList() vs PlayerActivityDto#getEndingBalanceList()

I tried giving these lists their own setters and getters, but it doesn’t seem to help.

EDIT: I have found a workaround

To fix this issue, I had to create a new class to wrap the list in.

PlayerActivityDto

@Builder
public class PlayerActivityDto {
    @JacksonXmlProperty(localName = "playerActivityId", isAttribute = true)
    private String brandId;

    @JacksonXmlProperty(localName = "player")
    private PlayerDto player;

    @JacksonXmlProperty(localName = "playerActivityDetail")
    private PlayerActivityDetailDto playerActivityDetail;

    @JacksonXmlProperty(localName = "startingBalanceList")
    private SummaryBalanceListWrapper startingBalanceList;

    @JacksonXmlProperty(localName = "endingBalanceList")
    private SummaryBalanceListWrapper endingBalanceList;

    @JacksonXmlProperty(localName = "playerMovement")
    @JacksonXmlElementWrapper(localName = "playerMovementList")
    private List<FundsMovementDto> playerMovementList;
}

SummaryListWrapper

@Builder
public class SummaryBalanceListWrapper {
    @JacksonXmlElementWrapper(useWrapping = false)
    @JacksonXmlProperty(localName = "summaryBalance")
    private List<SummaryBalanceDto> summaryBalanceList;
}

It seems this issue won’t be addressed by Jackson devs soon, so I hope this helps to other developers running into the same issue.