JAXB XML中的編組多余元素

Question

我有以下Employee類，需要以XML格式表示

雇員：

@XmlRootElement(name="employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee {

private int id;
private String firstName;
private String lastName;
private int income;

private Map<Integer,Employee> employeeMap=new HashMap<>();    
//getters and setters
}

編組代碼：

public class MarshallExample {

public static void main(String[] args) throws JAXBException {

    Map<Integer,Employee> empMap=new HashMap<>();

    Employee emp1=new Employee();
    emp1.setId(1);
    emp1.setFirstName("aa");
    emp1.setLastName("bb");
    emp1.setIncome(1000);

    Employee emp2=new Employee();
    emp2.setId(2);
    emp2.setFirstName("xx");
    emp2.setLastName("yy");
    emp2.setIncome(2000);

    empMap.put(1, emp1);
    empMap.put(2, emp2);

    Employee emp=new Employee();
    emp.setEmployeeMap(empMap);

    JAXBContext jaxbContext=JAXBContext.newInstance(Employee.class);
    Marshaller jaxbMarshaller=jaxbContext.createMarshaller();

    jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
    jaxbMarshaller.marshal(emp, System.out);


}

}

XML輸出：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<employee>
<id>0</id>
<income>0</income>
<employeeMap>
    <entry>
        <key>1</key>
        <value>
            <id>1</id>
            <firstName>aa</firstName>
            <lastName>bb</lastName>
            <income>1000</income>
            <employeeMap/>
        </value>
    </entry>
    <entry>
        <key>2</key>
        <value>
            <id>2</id>
            <firstName>xx</firstName>
            <lastName>yy</lastName>
            <income>2000</income>
            <employeeMap/>
        </value>
    </entry>
</employeeMap>
</employee>

無法弄清為什么<id> 0 </id>和<income> 0 </income>元素為什么出現在根元素內的輸出中，而不僅僅是兩個雇員實例。

Answer 1

這是因為它們是int值，不能為null 。 將其更改為Integer，它們將不再呈現。

@XmlRootElement(name="employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee {

private Integer id;
private String firstName;
private String lastName;
private Integer income;

private Map<Integer,Employee> employeeMap=new HashMap<>();    
//getters and Setters

}