1 package com.qcf.pox; 2  3 import java.util.HashSet; 4 import java.util.Set; 5  6 import javax.persistence.CascadeType; 7 import javax.persistence.Column; 8 import javax.persistence.Entity; 9 import javax.persistence.GeneratedValue;10 import javax.persistence.GenerationType;11 import javax.persistence.Id;12 import javax.persistence.OneToMany;13 import javax.persistence.Table;14 15 import org.hibernate.annotations.Cascade;16 import org.hibernate.annotations.Formula;17 //实体类18 @Entity19 @Table(name="_class")20 public class ClassName {21     @Id22     @GeneratedValue(strategy=GenerationType.AUTO)//设置id生成方式23     private int classid;24     @Column(name="classname")25     private String name;26     /*27      * 用一个查询语句动态的生成一个类的属性. 表示这个属性是一个虚拟的列，表中并没有这个列。需要通过查询语句计算出来。28      */29     //@Formula("(select count(*) from student s where s.className_classid=classid)")30     private int num;31     /*32      * mappedBy指定谁来维护关系，mappedBy在一方表示由多方来维护关系，在进行操作时要注意不要使用这一方来save,update等操作33      */34     @OneToMany(mappedBy="classname",cascade=CascadeType.ALL)35     private Set<Student> students=new HashSet<Student>();36     37     public ClassName(int classid, String name, int num, Set<Student> students) {38         super();39         this.classid = classid;40         this.name = name;41         this.num = num;42         this.students = students;43     }44     public Set<Student> getStudents() {45         return students;46     }47     public void setStudents(Set<Student> students) {48         this.students = students;49     }50     public int getClassid() {51         return classid;52     }53     public void setClassid(int classid) {54         this.classid = classid;55     }56     public String getName() {57         return name;58     }59     public void setName(String name) {60         this.name = name;61     }62     public int getNum() {63         return num;64     }65     public void setNum(int num) {66         this.num = num;67     }68     public ClassName(int classid, String name, int num) {69         super();70         this.classid = classid;71         this.name = name;72         this.num = num;73     }74     public ClassName() {75         super();76     }77     78 79 }

 1 package com.qcf.pox; 2  3 import java.util.Date; 4  5 import javax.persistence.Entity; 6 import javax.persistence.FetchType; 7 import javax.persistence.GeneratedValue; 8 import javax.persistence.GenerationType; 9 import javax.persistence.Id;10 import javax.persistence.ManyToOne;11 12 @Entity 13 public class Student {14     15     @Id16     @GeneratedValue(strategy=GenerationType.AUTO)//代表主键的生成策略17     private int stuno;18     private String stuname;19     private Date birthday;20     21     @ManyToOne22     private ClassName classname;23     public int getStuno() {24         return stuno;25     }26     public ClassName getClassName() {27         return classname;28     }29     public void setClassName(ClassName className) {30         this.classname = className;31     }32     public void setStuno(int stuno) {33         this.stuno = stuno;34     }35     public String getStuname() {36         return stuname;37     }38     public void setStuname(String stuname) {39         this.stuname = stuname;40     }41     public Date getBirthday() {42         return birthday;43     }44     public void setBirthday(Date birthday) {45         this.birthday = birthday;46     }47     public Student() {48         super();49     }50     public Student(int stuno, String stuname, Date birthday) {51         super();52         this.stuno = stuno;53         this.stuname = stuname;54         this.birthday = birthday;55     }56     57 }

1         <!-- 引入映射文件 -->2 3         <mapping class="com.qcf.pox.Student"/>4         <mapping class="com.qcf.pox.ClassName"/>

 1 package com.qcf.test; 2  3 import java.util.Date; 4  5 import org.hibernate.Session; 6 import org.hibernate.SessionFactory; 7 import org.hibernate.Transaction; 8 import org.hibernate.cfg.AnnotationConfiguration; 9 import org.hibernate.cfg.Configuration;10 11 import com.qcf.pox.ClassName;12 import com.qcf.pox.Student;13 14 public class TestManyToOne {15     public static void main(String[] args) {16         //获取hibernate配置文件并取得session对象17         Configuration configuration=new AnnotationConfiguration().configure();18         SessionFactory factory=configuration.buildSessionFactory();19         Session session=factory.openSession();20         //开启事务21         Transaction transaction=session.beginTransaction();22         //创建classname实例23         ClassName className=new ClassName();24         className.setName("java");25         26         //创建student实例27         Student student=new Student();28         29         student.setStuname("zhangsan");30         student.setBirthday(new Date());31         student.setClassName(className);32         session.save(className);33         session.save(student);34         //提交事务35         transaction.commit();36         //关闭session37         session.close();38     }39 40 }