Hibernate学习手记（5）--关联映射
关于Hibernate的关联映射（annotation专版）
举一典型到老掉牙的例子说明：Teacher、Student与Course之间的关系。
Teacher与Course是一对一关系；
Student与Course是一对多关系；
Teacher与Student是多对多关系；
....................
@Entity
@Table(name="Student")
publicclassStudent{
privateintid;
privateStringname;
privateStringsex;
privateCoursecourse;
privateSet<Teacher>teachers=newHashSet<Teacher>();
//建立Student与Teacher的双向多对多关联
@ManyToMany(mappedBy="students")
publicSet<Teacher>getTeachers(){
returnteachers;
}
publicvoidsetTeachers(Set<Teacher>teachers){
this.teachers=teachers;
}
//单向多对一关联
@ManyToOne
publicCoursegetCourse(){
returncourse;
}
publicvoidsetCourse(Coursecourse){
this.course=course;
}
@Id
@Column(name="s_id")
publicintgetId(){
returnid;
}
@Column(name="s_name")
publicStringgetName(){
returnname;
}
@Column(name="s_sex")
publicStringgetSex(){
returnsex;
}
.............
}
..............................................
@Entity
@Table(name="Teacher")
publicclassTeacher{
privateintid;
privateStringname;
privateStringsex;
privateStringtitle;
privateCoursecourse;
privateSet<Student>students=newHashSet<Student>();
//Teacher与Student的单向多对多联系
@ManyToMany
@JoinTable(name="t_s",
joinColumns={@JoinColumn(name="t_id")},
inverseJoinColumns={@JoinColumn(name="s_id")}
)
//设置多对多关系的中间表，其中joinColumns属性里面指向本实体数据表的关联字段，
//inverseJoinColumns属性则指向中间表的另一关联字段对应的数据表的关联字段
publicSet<Student>getStudents(){
returnstudents;
}
publicvoidsetStudents(Set<Student>students){
this.students=students;
}
//Teacher与Course的一对一关联
@OneToOne
@JoinColumn(name="Course_id")
//JoinColumn，指定Course表的外键
publicCoursegetCourse(){
returncourse;
}
publicvoidsetCourse(Coursecourse){
this.course=course;
}
@Id
@Column(name="t_id")
publicintgetId(){
returnid;
}
@Column(name="t_name")
publicStringgetName(){
returnname;
}
@Column(name="t_sex")
publicStringgetSex(){
returnsex;
}
@Column(name="t_title")
publicStringgetTitle(){
returntitle;
}
..................
}
..........................
@Entity
@Table(name="Course")
publicclassCourse{
privateintid;
privateStringname;
privateStringscore;
privateSet<Student>student=newHashSet<Student>();
privateTeacherteacher;
/*
*为实现双向的一对一关联，添加属性mappedBy，使确定该实体被映射在teacher中的course属性上，主导放在多的一方
**/
@OneToOne(mappedBy="course")
publicTeachergetTeacher(){
returnteacher;
}
publicvoidsetTeacher(Teacherteacher){
this.teacher=teacher;
}
/*
*为实现双向的多对一关联，添加属性mappedBy，使确定该实体被映射在student中的course属性上，主导放在多的一方
**/
@OneToMany(mappedBy="course")
//单向一对多关联
//@JoinColumn(name="Course_id")
publicSet<Student>getStudent(){
returnstudent;
}
publicvoidsetStudent(Set<Student>student){
this.student=student;
}
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