gistfile1.txt

public class Student {
...
}

public class FrontEndCode {
...
    public void updateStudentWithNewName(final Id id, final String firstName, final String lastName) {
        final Student student = bec.getStudent(id);
        student.setFirstName(firstName);
        student.setLastName(lastName);
        bec.saveStudent(student);
    }
...
}

public class BackEndCode {
...
    public Student getStudent(final Id id) {
        return em.find(Student.class, id);
    }
    public void saveStudent(final Student student) {
        em.merge(student);
    }
...
}