JAXB Unmarshalling a List

Question

I am having trouble unmarshalling a simple list of elements with JAXB. I have simplified my model further and still have a problem.

I have 2 element classes, a Classroom element and a Student element. I have modelled them in Java like below:

@XmlRootElement(name = "classroom", namespace = "http://www.info.com/school/model")
@XmlAccessorType(XmlAccessType.FIELD)
public class Classroom {
    @XmlElementWrapper(name = "students")
    @XmlElement(name = "student", type = Student.class)
    private List<Student> students;

    public List<Student> getStudents() {
        return students;
    }

    public void setStudents(List<Student> students) {
        this.students = students;
    }   
}

@XmlAccessorType(XmlAccessType.FIELD)
public class Student {
    private String name;
    private String gender;
    private Integer age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }   
}

When I try to unmarshal the classroom element, it is unable to unmarshal the list of students. For example the following code should print out to System out "Number of Pupils is: 2", yet when I run it I get "Number of Pupils is: 0".

Is someone able to point me in the right direction for configuring the JAXB annotations so that I can unmarshal this?

I have even added a toString methof call on the JAXB context and I can see that the Student class is listed as well.

public static void main(String[] args) {
        SimpleJaxbTestForLists sjtfl = new SimpleJaxbTestForLists();
        sjtfl.unmarshal("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><classroom xmlns=\"http://www.info.com/school/model\"><students><student><name>Test Student 1</name><gender>Male</gender><age>12</age></student><student><name>Test Student 2</name><gender>Female</gender><age>12</age></student></students></classroom>");

    }

    public void unmarshal(String xmlContent) {
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(Classroom.class);

            System.out.println(jaxbContext.toString());
            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();


            StringReader reader = new StringReader(xmlContent);
            Classroom classroom = (Classroom) jaxbUnmarshaller.unmarshal(reader);

            System.out.println("Number of Pupils is: " + classroom.getStudents().size());
        } catch (JAXBException ex) {
            ex.printStackTrace();
        }
    }

Answer 1

Since your XML document specifies a default namespace, you can leverage a package level @XmlSchema annotation to map the namespace qualification:

package-info.java

@XmlSchema(
    namespace = "http://www.info.com/school/model",
    elementFormDefault = XmlNsForm.QUALIFIED)
package example;

import javax.xml.bind.annotation.XmlNsForm;
import javax.xml.bind.annotation.XmlSchema;

For More Information

You can read more about JAXB and namespace qualification on my blog:

• http://blog.bdoughan.com/2010/08/jaxb-namespaces.html