hibernate之关于一对一单向,双向关联映射
@Entity @Table(name="t_user") publicclass User { private Integer id; private String name; private Card card; @OneToOne @JoinColumn(name="card_id",unique=true)//name是自定义关联外键的列名 public Card getCard() { returncard; } publicvoid setCard(Card card) { this.card = card; } @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="name") public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; }
@Entity @Table(name="t_card") publicclass Card { private Integer id; private String num; @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="card_id") public String getNum() { returnnum; } publicvoid setNum(Stringnum) { this.num = num; } }
publicclass Group { private Integer id; private String name; public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } }
publicclass Person { private Integer id; private String name; private Integer age; private Group group; public Group getGroup() { returngroup; } publicvoid setGroup(Groupgroup) { this.group = group; } public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } public String getName() { return name; } public void setName(Stringname) { this.name = name; } public Integer getAge() { return age; } publicvoid setAge(Integer age){ this.age = age; } }
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="csg.hibernate.entity"> <class name="Group" table="t_group"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> </class> </hibernate-mapping>
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="csg.hibernate.entity"> <class name="Person" table="t_person"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> <property name="age" /> <many-to-one name="group" column="group_id" unique="true" not-null="true" /> </class> </hibernate-mapping>
@Entity @Table(name="t_user") publicclass User { private Integer id; private String name; private Card card; @OneToOne @JoinColumn(name="card_id",unique=true)//name主要是自定义关联外键的列名 public Card getCard() { returncard; } publicvoid setCard(Cardcard) { this.card = card; } @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="name") public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } }
@Entity @Table(name="t_card") publicclass Card { private Integer id; private String num; private User user; @OneToOne(mappedBy="card")//mappedBy的意思是指定User中的card作为关联外键,否则User和Card都会出现外键 public User getUser() { returnuser; } publicvoid setUser(Useruser) { this.user = user; } @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="card_id") public String getNum() { returnnum; } publicvoid setNum(Stringnum) { this.num = num; } }
Ok?那么我们可以看到在Annotaions中的配置都是ont-to-one,那么我们在xml中的配置呢?
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="csg.hibernate.entity"> <class name="Person" table="t_person"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> <property name="age" /> <many-to-one name="group" column="group_id" unique="true" not-null="true" /> </class> </hibernate-mapping>
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="csg.hibernate.entity"> <class name="Group" table="t_group"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> <!-- many-to-one这种配置会分别在两个表中都产生外键,造成数据的多余,通常我们采用one-to-one的形式在xml中配置 --> <many-to-one name="Person" column="person_id" unique="true" /> <!-- <one-to-onename="person"property-ref="group"/> --> </class> </hibernate-mapping>
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