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hibernate中对象与对象的关系(二):list,一对一,多对多
①:list 还是用学生和班级举例子,list是将学生添加进list集合时的顺序
Clazz类
public class Clazz { private Long id; private String name; private List<Student> stus = new ArrayList<>(); }
Student类:
public class Student { private Long id; private String name; private Clazz clz;//Clazz类为Student的字段 }
Clazz.hbm.xml;
<hibernate-mapping package="objectn.exus.s3_list"> <class name="Clazz"> <id name="id" column="c_id"> <generator class="native"/> </id> <property name="name" />
<list name="stus"> <key column="c_id"></key> <!-- list是有序的,将学生对象添加到list集合的顺序 --> <index column="index123" ></index> <one-to-many class="Student"/> </list>
</class>
</hibernate-mapping>
Student.hbm.xml;
<hibernate-mapping package="objectn.exus.s3_list"> <class name="Student"> <id name="id"> <generator class="native"/> </id> <property name="name" /> <!-- 多对一,name为类中的变量 ,column为生成的列名--> <many-to-one name="clz" column="c_id"></many-to-one> </class> </hibernate-mapping>
②:一对一 即身份证号对应每一个人
IDCard类:
public class IDCard { private String name; private Long id; private Person per; }
Person类:
public class Person { private Long id; private String name; private IDCard card; }
IDcard.hbm.xml;
<hibernate-mapping package="objectn.exus.s4_one2one"> <class name="IDCard"> <id name="id" column="c_id"> <generator class="foreign"> <param name="property">per</param> </generator> </id> <property name="name" /> <!-- constrained:添加一个主键约束 --> <one-to-one name="per" constrained="true"/> </class> </hibernate-mapping>
person.hbm.xml;
<hibernate-mapping package="objectn.exus.s4_one2one"> <class name="Person"> <id name="id"> <generator class="native"/> </id> <property name="name" /> <one-to-one name="card"/> </class> </hibernate-mapping>
测试类:
public void testsave12() { IDCard card = new IDCard("asdasd"); Person p = new Person("张三"); card.setPer(p); p.setCard(card); Session session = HibernateUtils.getSession(); Transaction transaction = session.beginTransaction(); session.save(p);//先保存主键 session.save(card); transaction.commit(); session.close(); }
③:多对多,即学生和老师的关系
Student类:
public class Student { private Long id; private String name; private Set<Teacher> teac = new HashSet<>(); }
Teacher类:
public class Teacher { private Long id; private String name; private Set<Student> stus = new HashSet<>(); }
Student.hbm.xml;
<hibernate-mapping package="objectn.exus.s5_many2many"> <class name="Student"> <id name="id" column="s_id"> <generator class="native"></generator> </id> <property name="name" /> <!-- t_tea_stu: 设置中间表的表名 --> <set name="teac" table="t_tea_stu" > <!-- key:代表中间表的和当前对象对应的ID的列名 设置中间表的那一列关联到当前表 --> <key column="id_stu"/> <!-- class: 设置对方的类名 column: 代表对方对象在中间表的列名 设置中间表的哪一列关联到对方的表 --> <many-to-many class="Teacher" column="id_tea" ></many-to-many> </set> </class> </hibernate-mapping>
teacher.hbm.xml;
<hibernate-mapping package="objectn.exus.s5_many2many"> <class name="Teacher"> <id name="id"> <generator class="native"/> </id> <property name="name" /> <set name="stus" table="t_tea_stu"> <key column="id_tea"></key> <many-to-many class="Student" column="id_stu"></many-to-many> </set> </class> </hibernate-mapping>
hibernate中对象与对象的关系(二):list,一对一,多对多
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