兩個實體類

public class Grade implements Serializable {
    private int gid;
    private String gname;
    private String gdesc;
    //在"一"方定義"多"方的集合
    private Set<Student> students=new HashSet<Student>();

private int sid;
    private String sname;
    private String sex;
    private Grade grade;
 

對映檔案填寫相應的one-to-many，many-to-one

<!-- 配置一對多關聯關係 -->
  <set  name="students" table="student" inverse="true"          cascade="all">
          <key column="gid"></key>
          <!-- 指定對應實體類 -->
          <one-to-many class="hibernatehand.entity.Student" />
 </set
 
>

 <!-- 配置多對一關聯關係-->
<many-to-one name="grade"  column="gid" class="hibernatehand.entity.Grade"    cascade="all"/>

測試類也需要配置相應關聯關係

    public static void add(){
    Grade g2=new Grade("2班", "JAVA軟體開發2班");
        Grade g=new Grade("JAVA一班", "JAVA軟體開發一班");
        Student s1=new Student("張1"
 
, "男");
        Student s2=new Student("張2", "女");
        Student s3=new Student("張3", "女");
        //配置雙方關聯關係
        s1.setGrade(g);
        s2.setGrade(g);
        s3.setGrade(g2);
        g.getStudents().add(s2);
        g.getStudents().add(s2);
        g2.getStudents().add(s3);

        Session session=HibernatehandUtil5.getSession(); 
        Transaction ts=session.beginTransaction();
        session.save(g);
        session.save(g2);

        ts.commit(); 
        HibernatehandUtil5.closeSession(session);  
    }

這樣雙向關聯關係就完成了
cascade=”all” 級聯操作 在儲存班級的同時也儲存的班級裡的學生
inverse=”true”通常在”一”方設定為true這樣關聯關係由多方維護
好處如下：

執行add方法

//inverse="false"
Hibernate: select max(gid) from grade
Hibernate: select max(sid) from student
Hibernate: insert into cart.grade (gname, gdesc, gid) values (?, ?, ?)
Hibernate: insert into cart.student (sname, sex, gid, sid) values (?, ?, ?, ?)
Hibernate: insert into cart.grade (gname, gdesc, gid) values (?, ?, ?)
Hibernate: insert into cart.student (sname, sex, gid, sid) values (?, ?, ?, ?)
Hibernate: update cart.student set gid=? where sid=?
Hibernate: update cart.student set gid=? where sid=?

//inverse="true"
Hibernate: select max(gid) from grade
Hibernate: select max(sid) from student
Hibernate: insert into cart.grade (gname, gdesc, gid) values (?, ?, ?)
Hibernate: insert into cart.student (sname, sex, gid, sid) values (?, ?, ?, ?)
Hibernate: insert into cart.grade (gname, gdesc, gid) values (?, ?, ?)
Hibernate: insert into cart.student (sname, sex, gid, sid) values (?, ?, ?, ?)

少執行了兩條update 語句但是結果相同； 因為是根據關聯關係把學生和班級都存進資料庫；所以update去更新學生表裡的學生-班級的關係毫無必要