使用 JAXB 解组到 POJO 后，列表返回为 null

Question

I am trying to unmarshall an XML into Java POJO using JAXB, all elements are getting unmarshalled fine except for the lists(listId1 and listId2), following is the xml, the pojo classes and the business class.

<?xml version="1.0" encoding="UTF-8"?>
<abacus-1.0-snapshot xmlns="urn:xxxxxxx">
    <rules>
        <rule>
            <name>rule1</name>
            <errorType>WARNING</errorType>
            <flag>true</flag>
            <startDate>2020-05-19</startDate>
            <listId1>
                <id>100101</id>
                <id>100102</id>
            </listId1>
            <listId2>
                <id>100103</id>
                <id>100104</id>
            </listId2>
        </rule>
        <rule>
            <name>rule2</name>
            <errorType>ERROR</errorType>
            <flag>false</flag>
            <startDate>2020-05-20</startDate>
            <listId1>
                <id>100105</id>
                <id>100106</id>
            </listId1>
            <listId2>
                <id>100107</id>
                <id>100107</id>
            </listId2>
        </rule>
    </rules>
</abacus-1.0-snapshot>

将 <rules> 元素映射到 Rules.java 的 Rules.java

@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "rules", namespace = "urn:xxxxxxx")
public class RulesPOJO
{

    @XmlElement(name = "rule", namespace = "urn:xxxxxxx")
    private final List<rulePOJO> rulesPOJO = new ArrayList<rulePOJO>();

    public List<rulePOJO> getRulesPOJO()
    {
        return rulesPOJO;
    }
}

Rule.java class 用于 map <rule> 元素到 Rule.Z93F725A04423FE1C886ZF

@XmlAccessorType(XmlAccessType.NONE)
public class RulePOJO
{

    @XmlElement(namespace = "urx:xxxxx")
    private final String name = null;
     
    @XmlElement(namespace = "urx:xxxxx")
    private final String errorType = null;
    
    @XmlElement(namespace = "urx:xxxxx")
    private final Date startDate = null;
    
    @XmlElement(name = "listId1", namespace = "urx:xxxxx")
    private final List<Long> listId1 = new ArrayList<>();
    
    @XmlElement(name = "listId2", namespace = "urx:xxxxx")
    private final List<Long> listId2 = new ArrayList<>();

    public String getName()
    {
        return name;
    }

    public errorType getErrorType()
    {
        return errorType;
    }

    public Boolean getFlag()
    {
        return flag;
    }

    public Date getStartDate()
    {
        return startDate;
    }

    public List<Long> getListId1()
    {
        return listId1;
    }

    public List<Long> getListId2()
    {
        return listId2;
    }
}

业务 class 用于将 xml 解组到 pojo

public class Retriever() throws JAXBException
    {
        Document document = Configuration.load(URI.create("urn:xxxxxx"));

        Unmarshaller unmarshaller = JAXBContext.newInstance(RulesPOJO.class).createUnmarshaller();
        RulesPOJO rulesPOJO = (RulesPOJO) unmarshaller
                .unmarshal(document.getElementsByTagName("Rules").item(0));
        for(RulePOJO rulePOJO : RulesPOJO.getRulesPOJO())
        {
            // the following are coming back null
            List<Long> listId1 = rulePOJO.getListId1();
            List<Long> listId2 = rulePOJO.getListId2();
        }
    }

谢谢！

Answer 1

正如评论中所讨论的， id是被视为 arraylist 的重复元素，如给定链接https://howtodoinjava.com/jaxb/xmlelementwrapper-annotation/中所述。 您可以使用XMLElementWrapper和XMLElement类型的注释来表示包装器和子元素。