Jackson XML无法正确反序列化Jakarta的XmlElements字段

使用Jackson XML进行Jakarta反序列化时，带有@XmlElements注解的字段始终返回null，但仅用@XmlElement的普通字段能正常解析。相关代码如下：

Java实体类代码 #

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "posinfo"
})
@XmlRootElement(name = "PUSH")
public class PUSH {

    @XmlElement(name = "posinfo")
    protected List<PosinfoType> posinfo;

    // 省略getter/setter等方法
}


@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "posinfoType", propOrder = {
    "delayAndINITAndARRIVAL",
    "delimiterAndAny"
})
public class PosinfoType {

    @XmlElements({
        @XmlElement(name = "DELAY", type = DELAYType.class),
        @XmlElement(name = "INIT", type = INITType.class),
        @XmlElement(name = "ARRIVAL", type = ARRIVALType.class),
        @XmlElement(name = "ONSTOP", type = ONSTOPType.class),
        @XmlElement(name = "DEPARTURE", type = DEPARTUREType.class),
        @XmlElement(name = "ONROUTE", type = ONROUTEType.class),
        @XmlElement(name = "ONPATH", type = ONPATHType.class),
        @XmlElement(name = "OFFROUTE", type = OFFROUTEType.class),
        @XmlElement(name = "END", type = ENDType.class)
    })
    protected List<Object> delayAndINITAndARRIVAL;
    @XmlElementRef(name = "delimiter", namespace = "http://example.com/tmi8/core", type = Delimiter.class, required = false)
    @XmlAnyElement(lax = true)
    protected List<Object> delimiterAndAny;

    // 省略getter/setter等方法
 }

待解析的XML片段 #

<posinfo>
    <ONROUTE>
        <timestamp>2024-05-14T16:18:14+00:00</timestamp>
        <source>VEHICLE</source>
    </ONROUTE>
    <ONSTOP>
        <timestamp>2024-05-14T16:18:14+00:00</timestamp>
        <source>VEHICLE</source>
    </ONSTOP>
    <ARRIVAL>
        <timestamp>2024-05-14T16:18:16+00:00</timestamp>
        <source>VEHICLE</source>
    </ARRIVAL>
</posinfo>

Jackson配置代码（Kotlin） #

object JacksonJaxbUtils {
    val objectMapperXml: ObjectMapper = XmlMapper.builder().apply {
        defaultUseWrapper(false)

        enable(ToXmlGenerator.Feature.WRITE_XML_DECLARATION)

        addModule(JakartaXmlBindAnnotationModule())

        disable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE)
        disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
        disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
        serializationInclusion(JsonInclude.Include.NON_EMPTY)
        addModule(
            JavaTimeModule().apply {
                addSerializer(XMLGregorianCalendar::class.java, XMLGregorianCalendarSerializer())
            }
        )
    }.build()

    class XMLGregorianCalendarSerializer : JsonSerializer<XMLGregorianCalendar>() {
        override fun serialize(value: XMLGregorianCalendar, generator: JsonGenerator, provider: SerializerProvider) {
            generator.writeString(value.toXMLFormat())
        }
    }
}

• 版本兼容性检查：确保jackson-module-jakarta-xmlbind-annotations与jackson-dataformat-xml版本完全一致，版本不匹配会导致JAXB注解无法被正确识别。
• 显式初始化列表：Jackson不会自动初始化空列表，需在PosinfoType中为字段赋值：

  @XmlElements({
      // 注解内容不变
  })
  protected List<Object> delayAndINITAndARRIVAL = new ArrayList<>();
  

• 调整包装器配置：全局defaultUseWrapper(false)会干扰@XmlElements字段的解析逻辑，可直接移除该配置；若必须保留，需给目标字段添加注解明确禁用包装：

  @XmlElements({
      // 注解内容不变
  })
  @JacksonXmlElementWrapper(useWrapping = false)
  protected List<Object> delayAndINITAndARRIVAL = new ArrayList<>();
  

• 验证子类型注解：确认DELAYType、ONROUTEType等子类都正确添加了JAXB注解（如@XmlType或@XmlRootElement），否则Jackson无法完成XML元素到Java类的映射。

内容的提问来源于stack exchange，提问作者MrAndre