Hibernate的单向N-N关联（四）

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N-N关联需要使用@ManyToMany注解来修饰代表关联实体的集合。同时，N-N关联必须使用连接表。下面是单向N-N关联的Person类。

@Entity@Table(name="person_inf")public class Person{// 标识属性@Id @Column(name="person_id")@GeneratedValue(strategy=GenerationType.IDENTITY)private Integer id;private String name;private int age;// 定义该Person实体所有关联的Address实体@ManyToMany(targetEntity=Address.class)// 映射连接表为person_address@JoinTable(name="person_address",// 定义连接表中名为person_id的外键列，该外键列参照当前实体对应表的主键列joinColumns=@JoinColumn(name="person_id"// 定义连接表中名为address_id的外键列，// 该外键列参照当前实体的关联实体对应表的主键列，没有指定unique=true, referencedColumnName="person_id"),inverseJoinColumns=@JoinColumn(name="address_id", referencedColumnName="address_id"))private Set<Address> addresses= new HashSet<>();// id的setter和getter方法public void setId(Integer id){this.id = id;}public Integer getId(){return this.id;}// name的setter和getter方法public void setName(String name){this.name = name;}public String getName(){return this.name;}// age的setter和getter方法public void setAge(int age){this.age = age;}public int getAge(){return this.age;}// addresses的setter和getter方法public void setAddresses(Set<Address> addresses){this.addresses = addresses;}public Set<Address> getAddresses(){return this.addresses;}}

下而Address的实体类。

@Entity@Table(name="address_inf")public class Address{// 标识属性@Id @Column(name="address_id")@GeneratedValue(strategy=GenerationType.IDENTITY)private int addressId;// 定义地址详细信息的成员变量private String addressDetail;// 无参数的构造器public Address(){}// 初始化全部成员变量的构造器public Address(String addressDetail){this.addressDetail = addressDetail;}// addressId的setter和getter方法public void setAddressId(int addressId){this.addressId = addressId;}public int getAddressId(){return this.addressId;}// addressDetail的setter和getter方法public void setAddressDetail(String addressDetail){this.addressDetail = addressDetail;}public String getAddressDetail(){return this.addressDetail;}}

用下面的类来保存Person与Address.

public class PersonManager{public static void main(String[] args){PersonManager mgr = new PersonManager();mgr.testPerson();HibernateUtil.sessionFactory.close();}private void testPerson(){Session session = HibernateUtil.currentSession();Transaction tx = session.beginTransaction();// 创建一个Person对象Person p = new Person();// 设置Person的name为owenp.setName("owen");p.setAge(20);// 持久化Person对象session.save(p);// 创建一个瞬态的Address对象Address a = new Address("广州天河");// 设置Person和Address之间的关联关系p.getAddresses().add(a);// 再持久化Address对象session.persist(a);// 创建一个瞬态的Address对象Address a2 = new Address("上海虹口");// 设置Person和Address之间的关联关系p.getAddresses().add(a2);// 再持久化Address对象session.persist(a2);Person p2 = new Person();p2.setName("fkit");p2.setAge(29);p2.getAddresses().add(a2);session.save(p2);tx.commit();HibernateUtil.closeSession();}}

SQL语句如下。

Hibernate:     insert     into        person_inf        (age, name)     values        (?, ?)Hibernate:     insert     into        address_inf        (addressDetail)     values        (?)Hibernate:     insert     into        address_inf        (addressDetail)     values        (?)Hibernate:     insert     into        person_inf        (age, name)     values        (?, ?)Hibernate:     insert     into        person_address        (person_id, address_id)     values        (?, ?)Hibernate:     insert     into        person_address        (person_id, address_id)     values        (?, ?)Hibernate:     insert     into        person_address        (person_id, address_id)     values        (?, ?)

执行的结果图如下：

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