多对一（一对多）的双向关联
一个组（Group）有多个用户（User），进行多对一（一对多）的双向配置，在数据库中生成的表结构如下图：
Annotation配置：
Group:
1 package com.bjsxt.hibernate; 2 3 import java.util.HashSet; 4 import java.util.Set; 5 6 import javax.persistence.Entity; 7 import javax.persistence.GeneratedValue; 8 import javax.persistence.Id; 9 import javax.persistence.OneToMany; 10 import javax.persistence.Table; 11 12 @Entity 13 @Table(name="t_group") 14 public class Group { 15 private Integer id; 16 17 private String name; 18 19 private Set<User> users = new HashSet<User>(); 20 21 @Id 22 @GeneratedValue 23 public Integer getId() { 24 return id; 25 } 26 27 public void setId(Integer id) { 28 this.id = id; 29 } 30 31 public String getName() { 32 return name; 33 } 34 35 public void setName(String name) { 36 this.name = name; 37 } 38 39 @OneToMany(mappedBy="group")//表示和User是一对多的关系，并且以User的group属性为准，自己就不做映射配置了 40 public Set<User> getUsers() { 41 return users; 42 } 43 44 public void setUsers(Set<User> users) { 45 this.users = users; 46 } 47 }
User:
1 package com.bjsxt.hibernate; 2 3 import javax.persistence.Entity; 4 import javax.persistence.GeneratedValue; 5 import javax.persistence.Id; 6 import javax.persistence.JoinColumn; 7 import javax.persistence.ManyToOne; 8 import javax.persistence.Table; 9 10 @Entity 11 @Table(name="t_user") 12 public class User { 13 private Integer id; 14 15 private String name; 16 17 private Group group; 18 19 @Id 20 @GeneratedValue 21 public Integer getId() { 22 return id; 23 } 24 25 public void setId(Integer id) { 26 this.id = id; 27 } 28 29 public String getName() { 30 return name; 31 } 32 33 public void setName(String name) { 34 this.name = name; 35 } 36 37 @ManyToOne 38 @JoinColumn(name="group_ID")//指定列名为 group_ID 39 public Group getGroup() { 40 return group; 41 } 42 43 public void setGroup(Group group) { 44 this.group = group; 45 } 46 }
XML 配置：
Group:
1 package com.bjsxt.hibernate; 2 3 import java.util.HashSet; 4 import java.util.Set; 5 6 public class Group { 7 private Integer id; 8 9 private String name; 10 11 private Set<User> users = new HashSet<User>(); 12 13 public Integer getId() { 14 return id; 15 } 16 17 public void setId(Integer id) { 18 this.id = id; 19 } 20 21 public String getName() { 22 return name; 23 } 24 25 public void setName(String name) { 26 this.name = name; 27 } 28 29 public Set<User> getUsers() { 30 return users; 31 } 32 33 public void setUsers(Set<User> users) { 34 this.users = users; 35 } 36 }
Group.hbm.xml:
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC 3 "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 4 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 5 6 <hibernate-mapping package="com.bjsxt.hibernate"> 7 <class name="Group" table="t_group"> 8 <id name="id" column="id"> 9 <generator class="native"/> 10 </id> 11 <property name="name" column="name" /> 12 <set name="users"> 13 <key column="groupId"></key> 14 <one-to-many class="User"/> 15 </set> 16 </class> 17 </hibernate-mapping>
User:
1 package com.bjsxt.hibernate; 2 3 public class User { 4 private Integer id; 5 6 private String name; 7 8 private Group group; 9 10 public Integer getId() { 11 return id; 12 } 13 14 public void setId(Integer id) { 15 this.id = id; 16 } 17 18 public String getName() { 19 return name; 20 } 21 22 public void setName(String name) { 23 this.name = name; 24 } 25 26 public Group getGroup() { 27 return group; 28 } 29 30 public void setGroup(Group group) { 31 this.group = group; 32 } 33 }
User.hbm.xml
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC 3 "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 4 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 5 6 <hibernate-mapping package="com.bjsxt.hibernate"> 7 <class name="User" table="t_user"> 8 <id name="id" column="id"> 9 <generator class="native"/> 10 </id> 11 <property name="name" column="name" /> 12 <many-to-one name="group" column="groupId"></many-to-one> 13 </class> 14 </hibernate-mapping>
两个配置文件的 groupId 必须取名一致，否则会出现两个外键。
两种方式最后生成的SQL语句：
jar包链接: https://pan.baidu.com/s/1eSuw9Aq 密码: zrsy
开发链接: https://pan.baidu.com/s/1hsA73Ju 密码: 3q2b
