Hibenrate之多对多关联

Hibernate多对多关联可以分成单向和双向，多对多关系会借助中间表来保存映射信息，所以一般少用；

• 单向
  

实例：学生可以在多个学校就读过，多个学校也会有多个学生；

TStudent：

public class TStudent implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer stuId;
	private String name;
	private Set<TSchool> tschool;
        get()/set()

 TStudent.hbm.xml：

<hibernate-mapping package="com.keith.many2many">
	<class name="TStudent" table="TStudent">
		<id name="stuId">
			<generator class="native"/>
		</id>
	
		<property name="name" />
		
		<set name="tschool" table="stu_school_link" cascade="all">
			<key column="stuId"/>
			<many-to-many class="TSchool" column="schoolId"/>
		</set>
	</class>	
</hibernate-mapping>

 TSchool：

public class TSchool implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer schoolId;
	private String name;
        get()/set()
}

 TSchool.hbm.xml：

<hibernate-mapping package="com.keith.many2many">
	<class name="TSchool" table="TSchool">
		<id name="schoolId">
			<generator class="native"/>
		</id>
		<property name="name" />
	</class>	
</hibernate-mapping>

 测试：

//添加数据
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();

		TStudent student = new TStudent();
		student.setName("柯");

		Set<TSchool> schools = new HashSet<TSchool>();
		TSchool school = new TSchool();
		school.setName("小学");
		TSchool school1 = new TSchool();
		school1.setName("中学");
		TSchool school2 = new TSchool();
		school2.setName("大学");

		schools.add(school);
		schools.add(school1);
		schools.add(school2);
		student.setTschool(schools);
		
		session.save(student);
		session.getTransaction().commit();

//查询数据
		TStudent stu = (TStudent) session.load(TStudent.class, 1);
		System.out.println("student's Name：" + stu.getName());

		Iterator<TSchool> it = stu.getTschool().iterator();
		TSchool school = null;
		while (it.hasNext()) {
			school = it.next();
			System.out.println("student's school Name"+school.getName());
		}

•  双向，在TSchool一方加入TStudent对象；

TSchool：

public class TSchool implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer schoolId;
	private String name;
	private Set<TStudent> stus = new HashSet();
        get()/set()
}

 TSchool.hbm.xml：

<hibernate-mapping package="com.keith.many2many.doubleSide">
	<class name="TSchool" table="TSchool">
		<id name="schoolId">
			<generator class="native"/>
		</id>
	
		<property name="name" />
		<set name="stus" table="stu_school_link" cascade="save-update">
			<key column="schoolId"/>
			<many-to-many column="stuId" class="TStudent"/>
		</set>
	</class>	
</hibernate-mapping>

 TStudent：

public class TStudent implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer stuId;
	private String name;
	private Set<TSchool> tschool;
        get()/set();
}

 

TStudent.hbm.xml：

<hibernate-mapping package="com.keith.many2many.doubleSide">
	<class name="TStudent" table="TStudent">
		<id name="stuId">
			<generator class="native"/>
		</id>
	
		<property name="name" />
		
		<set name="tschool" table="stu_school_link" cascade="save-update">
		<!-- "stuId"：连接表中关联当前实体类的列名 -->
			<key column="stuId"/>
			<!-- "schoolId"：是连接表中关联本实体类的外键 -->
			<many-to-many class="TSchool" column="schoolId"/>
		</set>
	</class>	
</hibernate-mapping>

 附上测试类；