Spring Boot中Jackson序列化XML同名子元素列表引发异常

问题场景 #

在Spring Boot 3.3.5 + jackson-dataformat-xml v2.18.2环境下，PlayerActivityDto中的startingBalanceList和endingBalanceList两个列表，需要将子元素统一序列化为<summaryBalance>标签，但Jackson抛出InvalidDefinitionException，提示getter方法冲突。

异常信息：

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()

问题原因 #

两个列表字段均使用@JacksonXmlProperty(localName = "summaryBalance")，Jackson会将该注解的localName作为内部属性键，导致两个字段被识别为同一个属性，对应的getter方法因此产生冲突。

解决方案 #

提供三种可行方案，按需选择：

方案1：为列表字段指定唯一JSON属性名 #

通过@JsonProperty为每个列表指定唯一的内部属性名，同时保留XML子元素的名称配置：

import com.fasterxml.jackson.annotation.JsonProperty;
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
    @JsonProperty("startingBalanceList")
    @JacksonXmlElementWrapper(localName = "startingBalanceList")
    @JacksonXmlProperty(localName = "summaryBalance")
    private List<SummaryBalanceDto> startingBalanceList;

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

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

方案2：在子元素DTO上配置XML根元素名称 #

在SummaryBalanceDto类上添加@JacksonXmlRootElement指定子元素标签名，移除列表字段上的@JacksonXmlProperty：

// SummaryBalanceDto.java
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;

@JacksonXmlRootElement(localName = "summaryBalance")
public class SummaryBalanceDto {
    // 类字段及注解
}

// PlayerActivityDto.java中修改列表字段
@Setter
@Getter
@JacksonXmlElementWrapper(localName = "startingBalanceList")
private List<SummaryBalanceDto> startingBalanceList;

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

方案3：为Getter方法指定唯一属性名 #

利用Lombok的onMethod_参数，为自动生成的getter添加@JsonGetter，明确属性名：

import com.fasterxml.jackson.annotation.JsonGetter;
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;

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

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

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

效果验证 #

上述方案均可实现：

• 列表外层标签分别为<startingBalanceList>和<endingBalanceList>
• 列表内的子元素统一为<summaryBalance>
• 解决Jackson的getter冲突异常

内容的提问来源于stack exchange，提问作者ludvikjr