JAXB解组XML，在子元素中具有父元素

Question

I've looked and googled around but couldn't find an answer for my problem. I have an XML file with the following structure:

<!DOCTYPE persons [
    <!ELEMENT lastname (#PCDATA)>
    <!ELEMENT firstname (#PCDATA)>
    <!ELEMENT residence (#PCDATA)>
    <!ELEMENT children (person*)>
    <!ELEMENT person (firstname, (lastname?), (children?), (residence?))>
    <!ELEMENT persons (person+)>
    <!ATTLIST person id ID #REQUIRED>
    <!ATTLIST person friends IDREFS #IMPLIED>
    <!ATTLIST persons file CDATA #IMPLIED>
    ]>

<persons file="this">
    <person id="p-1">
        <firstname>Homer</firstname>
        <lastname>Simpson</lastname>
        <residence>Springfield</residence>
        <children>
            <person id="p-3">
                <firstname>Bart</firstname>
                <residence>Springfield</residence>
            </person>
        </children>
    </person>
    <person id="p-2" friends="p-1">
        <firstname>Ned</firstname>
        <lastname>Flanders</lastname>
        <residence>Springfield</residence>
    </person>
</persons>

My Java files are the following:

Persons.java

@XmlRootElement(name="persons")
public class Persons {

    @XmlAttribute(name="file")  
    private String file;
    @XmlElement(name="person")
    private List<Person> persons;

    /* setters and getters */
}

Person.java

public class Person {

    @XmlAttribute(name="id")
    private String id;
    @XmlAttribute(name="friends")
    private String friends;
    private String firstname;
    private String lastname;
    private String residence;
    private List<Children> children;

    /* getters and setters */
}

Children.java

public class Children {

    private List<Person> persons;

    /* getters and setters */
}

NOTE: I used annotations on the object variables because i didn't want to write down getters and setters. I know, that otherwise a @XmlAccessorType(XmlAccessType.FIELD) is necessary.

So <children> can actually have one or more <person> as a child. I think I got confused with the different Lists. When I simply test it by unmarshalling the given XML file with a simple System.out.println() command on every person I see every element and attribute with the correct value but person.getChildren() always returns null. What did I do wrong?

Answer 1

In your Children class, you've forgotten to add

@XmlElement(name="person")

to the list of persons inside children class. So it should looks like this:

public class Children {

    private List<Person> persons;

    public List<Person> getPersons() {
        return persons;
    }

    @XmlElement(name="person") // MISSING ANNOTATION
    public void setPersons(List<Person> persons) {
        this.persons = persons;
    }
}

After adding this my output is:

Persons = [
    file: this, 
    persons: [
        Person = [
            id=p-1, 
            freinds=null, 
            firstName=Homer, 
            lastName=Simpson, 
            residence=Springfield, 
            children=[
                Children = [
                    persons=[
                        Person = [
                            id=p-3, 
                            freinds=null, 
                            firstName=Bart, 
                            lastName=null, 
                            residence=Springfield, 
                            children=null
                        ]
                    ]
                ]
            ]
        ], 
        Person = [
            id=p-2, 
            freinds=p-1, 
            firstName=Ned, 
            lastName=Flanders, 
            residence=Springfield, 
            children=null
        ]
    ]
]