<input type="text" name="stu.subjects.subjectsName"/>

private int subjectsId;
private String subjectsName;

private int stuId;
    private String stuName;
    private String stuAddress;
    private Date stuJoinTime;
    private Card card;
    private Class clss;
    private Set<Subjects> subjects = new HashSet<Subjects>();

private Student stu = new Student();