Hibernate之关于多对多单向关联映射
【Hibernate】之关于多对多的单向关联映射
老师和学生,最典型的多对多关联,
Teacher和Student,所谓单向意思就是说,老师知道自己的教的是哪些学生而学生不知道是哪些老师教。也可以这么说,在查询的时候,通过老师可以级联查询出学生,但是通过学生不可以级联查询出老师!
而多对多最麻烦的是怎么自定义我们中间表的,表名和列名,这个是重要的!
Annotations配置
@Entity @Table(name="t_teacher") publicclass Teacher { private Integer id; private String name; private Set<Student> students=new HashSet<Student>();//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; } @ManyToMany @JoinTable(name="t_s_two",//自定义表名 joinColumns={@JoinColumn(name="teacher_id")},//自定义列名 inverseJoinColumns={@JoinColumn(name="student_id")})//反转,和Teacher对应的那个表的列名,也是自定义 public Set<Student>getStudents() { returnstudents; } publicvoidsetStudents(Set<Student> students) { this.students = students; } }
@Entity @Table(name="t_student") publicclass Student { private Integer id; private String name; private Integer age; @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integerid) { this.id = id; } @Column(name="s_name") public String getName() { returnname; } publicvoid setName(Stringname) { this.name = name; } @Column(name="s_age") public Integer getAge() { returnage; } publicvoid setAge(Integerage) { this.age = age; } }
XML配置
publicclass Teacher { private Integer id; private String name; private Set<Student> students=newHashSet<Student>();//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<Student>getStudents() { returnstudents; } publicvoidsetStudents(Set<Student> students) { this.students = students; } }
publicclass Student { 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; } }
<?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="Teacher" table="t_teacher"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> <set name="students" table="t_s_two"><!—-自定义表名--> <key column="teacher_id"/><!—自定义列名--> <many-to-many class="csg.hibernate.entity.Student" column="student_id"/><!—自定义列名--> </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="Student" table="t_student"> <id name="id"> <column name="id"/> <generator class="native" /> </id> <property name="name" /> <property name="age" /> </class> </hibernate-mapping>
以上就是XML的many-to-many(单向)的配置方法
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