hibernate之关于一对多单向关联映射
【hibernate】之关于一对多单向关联映射
基于外键的一对多关联映射!一对多,Group(组)对于Person(人),一个组可以有多个人!ok?
Hibernate主要有两种配置方法,一种是Annotations 一种是XML!
下面是Annotations的配置方法!
@Entity @Table(name="t_group") publicclass Group { private Integer id; private String name; private Set<Person> persons=newHashSet<Person>();//set不允许重复,最适合数据库模型 @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="t_name") public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } @OneToMany //加上@JoinColumn是为了防止Hibernate将一对多当做多对多来处理,产生中间表 @JoinColumn(name="group_id") public Set<Person>getPersons() { returnpersons; } publicvoidsetPersons(Set<Person> persons){ this.persons = persons; } }
@Entity @Table(name="t_person") publicclass Person { private Integer id; private String name; private Integer age; @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="t_name") public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } @Column(name="t_age") public Integer getAge() { returnage; } publicvoid setAge(Integerage) { this.age = age; } }
XML配置一对多的单向关联映射
publicclass Person { private Integer id; private String name; private Integer age; public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } public Integer getAge() { returnage; } publicvoid setAge(Integerage) { this.age = age; } }
publicclass Group { private Integer id; private String name; private Set<Person> persons=newHashSet<Person>();//set不允许重复,最适合数据库模型 public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } public Set<Person>getPersons() { returnpersons; } publicvoidsetPersons(Set<Person> persons) { this.persons = persons; } }
<?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" /> <set name="persons"> <key column="group_id"/> <one-to-many class="csg.hibernate.entity.Person"/> </set> </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" /> </class> </hibernate-mapping>
Ok,一对多单向关联映射的Annotations和XML配置方法!
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