Problème de cartographie HBM Hibernate

Question

J'ai les trois classes suivantes:

public class Student {
    private Integer studentId;
    private StudentSchool studentSchool;
    private School school;

    public Integer getStudentId() {
        return studentId;
    }
    public void setStudentId(Integer studentId) {
        this.studentId = studentId;
    }
    public StudentSchool getStudentSchool() {
        return studentSchool;
    }
    public School getSchool() {
        return school;
    }
    public void setSchool(School school) {
        this.school = school;
    }
}

public class StudentSchool {
    private Student student;
    private School school;  

    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
    public School getSchool() {
        return school;
    }
    public void setSchool(School school) {
        this.school = school;
    }
}

public class School {
    private Integer schoolId;
    private Set allStudents;

    public Integer getSchoolId() {
        return schoolId;
    }
    public void setSchoolId(Integer schoolId) {
        this.schoolId = schoolId;
    }
    public Set getAllStudents() {
        return allStudents;
    }
    public void setAllStudents(Set allStudents) {
        this.allStudents = allStudents;
    }
}

J'ai le DDL suivant:

create table Student (StudentId Integer);
create table StudentSchool (SchoolId Integer, StudentId Integer);
create table School (SchoolId Integer Primary Key);

J'ai les fichiers HBM suivants:

École.hbm.xml

<hibernate-mapping>
    <class name="School" table="School">
        <property name="schoolId" type="integer" />
        <set name="allStudents" table="StudentSchool" fetch="join">
            <key column="schoolId" />
            <composite-element class="StudentSchool">
                <parent name="school"/>
                <many-to-one name="student" column="studentId" not-null="true" class="Student" />
            </composite-element>
        </set>
    </class>
</hibernate-mapping>

Étudiant.hbm.xml

<hibernate-mapping>
    <class name="Student" table="Student">
        <property name="studentId" type="integer" />
        <one-to-one name="studentSchool" class="StudentSchool" />
        <!-- <one-to-one name="school" class="School" /> -->
    </class>
</hibernate-mapping>

Lorsque j'essaie de demander l'objet étudiant en fonction de l'école, je reçois l'exception suivante (même si j'ai une classe appelée "Studentschool" compilée dans mon chemin de classe):

org.hibernate.MappingException: persistent class not known: StudentSchool

Si je déconnecte la cartographie un à un à "l'école" et commentez la cartographie individuelle de "Studentschool", j'obtiens l'exception suivante:

<AST>:1:143: unexpected AST node: : java.lang.NullPointerException

Quelqu'un a-t-il des idées sur ce que j'ai fait de mal avec ma cartographie HBM? Merci!