更新
如果您指的persons是分组元素而不是根元素,则默认情况下JAXB (JSR-222)实现不会添加一个。
组(无分组元素)
package forum13305973;
import java.util.*;
import javax.xml.bind.annotation.*;
@XmlRootElement
public class Group {
    //many other fields
    @XmlElement(name="person")
    public List<Person> persons = new ArrayList<Person>();
}
人
package forum13305973;
public class Person {
    public String name;
}
演示
package forum13305973;
import javax.xml.bind.*;
public class Demo {
    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Group.class);
        Group group = new Group();
        Person person1 = new Person();
        person1.name = "Jane";
        group.persons.add(person1);
        Person person2 = new Person();
        person2.name = "John";
        group.persons.add(person2);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(group, System.out);
    }
}
输出
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<group>
    <person>
        <name>Jane</name>
    </person>
    <person>
        <name>John</name>
    </person>
</group>
组(带分组元素)
您需要添加@XmlElementWrapper注释以获取分组元素
package forum13305973;
import java.util.*;
import javax.xml.bind.annotation.*;
@XmlRootElement
public class Group {
    //many other fields
    @XmlElementWrapper
    @XmlElement(name="person")
    public List<Person> persons = new ArrayList<Person>();
}
输出(带分组元素)
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<group>
    <persons>
        <person>
            <name>Jane</name>
        </person>
        <person>
            <name>John</name>
        </person>
    </persons>
</group>
原始答案
您可以执行以下操作:
    JAXBContext jc = JAXBContext.newInstance(Person.class);
    Marshaller marshaller = jc.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); // format output
    marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true); // remove header
    for(Person person : group.persons) {
        marshaller.marshal(person, System.out);
    }