Hibernate映射set与List

1、对于set类型，如果集合中的元素是简单地类型，如字符串型，set使用另外一种映射方式：

team类：

 1 import java.util.HashSet;
 2 import java.util.Set;
 3 
 4 public class Team
 5 {
 6     private String id;
 7     
 8     private String teamName;
 9     
10     private Set students = new HashSet();
11 
12     public String getId()
13     {
14         return id;
15     }
16 
17     public void setId(String id)
18     {
19         this.id = id;
20     }
21 
22     public String getTeamName()
23     {
24         return teamName;
25     }
26 
27     public void setTeamName(String teamName)
28     {
29         this.teamName = teamName;
30     }
31 
32     public Set getStudents()
33     {
34         return students;
35     }
36 
37     public void setStudents(Set students)
38     {
39         this.students = students;
40     }
41 }

映射文件Team.hbm.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 
 5 <hibernate-mapping>
 6     
 7     <class name="com.cdtax.hibernate.Team" table="team">
 8         
 9         <id name="id" column="id" type="string">
10             <generator class="uuid">
11             </generator>
12         </id>
13             
14         <property name="teamName" column="teamname" type="string"></property>
15         
16         <set name="students" table="student">
17             <key column="team_id"></key>
18             <element column="name" type="string"></element>
19         </set>     
20     </class>
21     
22 </hibernate-mapping>

使用set标签，一般要对应另外一张表，对于set元素是简单类型的，使用element子标签。

表的创建：

1 create table student (team_id varchar(255) not null, name varchar(255))
2 create table team (id varchar(255) not null, teamname varchar(255), primary key (id))
3 alter table student add index FK8FFE823BB04F9E7 (team_id), add constraint FK8FFE823BB04F9E7 foreign key (team_id) references team (id)

测试类：

 1 import java.util.Map;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.SessionFactory;
 5 import org.hibernate.Transaction;
 6 import org.hibernate.cfg.Configuration;
 7 
 8 public class HibernateTest
 9 {
10     private static SessionFactory sessionFactory;
11     
12     static
13     {
14         try
15         {
16             sessionFactory = new Configuration().configure().buildSessionFactory();
17         }
18         catch(Exception ex)
19         {
20             ex.printStackTrace();
21         }
22     }
23     
24     public static void main(String[] args)
25     {
26                 
27         Session session = sessionFactory.openSession();
28         Transaction tx = null;
29         
30         try
31         {
32             tx = session.beginTransaction();
33             
34             Team team = new Team();
35             team.setTeamName("team");
36             
37             team.getStudents().add("zhangsan");
38             team.getStudents().add("lisi");
39             team.getStudents().add("wangwu");
40             
41             session.save(team);
42             
43             tx.commit();
44         }
45         catch(Exception ex)
46         {
47             if(null != tx)
48             {
49                 tx.rollback();
50             }
51             ex.printStackTrace();
52         }
53         finally
54         {
55             session.close();
56         }
57     }
58 }

运行结果：

hibernate: insert into team (teamname, id) values (?, ?)
Hibernate: insert into student (team_id, name) values (?, ?)
Hibernate: insert into student (team_id, name) values (?, ?)
Hibernate: insert into student (team_id, name) values (?, ?)

map与set标签中的element子标签映射的是原子类型（String，date，int，long。。。），即能够直接映射到数据库表字段上的类型，而one-to-many映射的则是实体类型，指的是无法映射到表的某个字段，而是要映射到整张表的类型。

2、List的映射，list元素可以重复，而且是有顺序的。

举例：

 1 import java.util.ArrayList;
 2 import java.util.List;
 3 
 4 public class Team
 5 {
 6     private String id;
 7     
 8     private String teamName;
 9     
10     private List students = new ArrayList();
11 
12     public String getId()
13     {
14         return id;
15     }
16 
17     public void setId(String id)
18     {
19         this.id = id;
20     }
21 
22     public String getTeamName()
23     {
24         return teamName;
25     }
26 
27     public void setTeamName(String teamName)
28     {
29         this.teamName = teamName;
30     }
31 
32     public List getStudents()
33     {
34         return students;
35     }
36 
37     public void setStudents(List students)
38     {
39         this.students = students;
40     }
41     
42 }

 1 public class Student
 2 {
 3     private String id;
 4     
 5     private String cardId;
 6     
 7     private String name;
 8     
 9     private int age;
10     
11     private Team team;
12 
13     public String getId()
14     {
15         return id;
16     }
17 
18     public void setId(String id)
19     {
20         this.id = id;
21     }
22 
23     public String getCardId()
24     {
25         return cardId;
26     }
27 
28     public void setCardId(String cardId)
29     {
30         this.cardId = cardId;
31     }
32 
33     public String getName()
34     {
35         return name;
36     }
37 
38     public void setName(String name)
39     {
40         this.name = name;
41     }
42 
43     public int getAge()
44     {
45         return age;
46     }
47 
48     public void setAge(int age)
49     {
50         this.age = age;
51     }
52 
53     public Team getTeam()
54     {
55         return team;
56     }
57 
58     public void setTeam(Team team)
59     {
60         this.team = team;
61     }
62     
63 }

对应的映射文件：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 
 5 <hibernate-mapping>
 6     
 7     <class name="com.cdtax.hibernate.Team" table="team">
 8         
 9         <id name="id" column="id" type="string">
10             <generator class="uuid">
11             </generator>
12         </id>
13             
14         <property name="teamName" column="teamname" type="string"></property>
15         
16         <list name="students" table="student" cascade="all">
17             <key column="team_id"></key>
18             <index column="index_"></index>
19             <one-to-many class="com.cdtax.hibernate.Student"/>
20         </list>
21     </class>
22     
23 </hibernate-mapping>

对于Team，多了一个list标签，其中的子标签index来指出数据库表中的一列来维护list的顺序，因为list是有序的，而数据库中表是没有顺序的，只能用一个字段来维护。

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 
 5 <hibernate-mapping>
 6     
 7     <class name="com.cdtax.hibernate.Student" table="student">
 8         
 9         <id name="id" column="id" type="string">
10             <generator class="uuid">
11             </generator>
12         </id>
13         <property name="cardId" column="card_id" type="string"></property>
14         <property name="name" column="name" type="string"></property>
15         <property name="age" column="age" type="integer"></property>
16         
17         <many-to-one name="team" column="team_id" class="com.cdtax.hibernate.Team" cascade="none" fetch="join"></many-to-one>     
18     </class>
19 </hibernate-mapping>

产生表的语句：

create table student (id varchar(255) not null, card_id varchar(255), name varchar(255), age integer, team_id varchar(255), index_ integer, primary key (id))
create table team (id varchar(255) not null, teamname varchar(255), primary key (id))

重点关注index_这一字段。

测试类：

 1 import java.util.Map;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.SessionFactory;
 5 import org.hibernate.Transaction;
 6 import org.hibernate.cfg.Configuration;
 7 
 8 public class HibernateTest
 9 {
10     private static SessionFactory sessionFactory;
11     
12     static
13     {
14         try
15         {
16             sessionFactory = new Configuration().configure().buildSessionFactory();
17         }
18         catch(Exception ex)
19         {
20             ex.printStackTrace();
21         }
22     }
23     
24     public static void main(String[] args)
25     {
26                 
27         Session session = sessionFactory.openSession();
28         Transaction tx = null;
29         
30         try
31         {
32             tx = session.beginTransaction();
33             
34             Team team = new Team();
35             team.setTeamName("team1");
36             
37             Team team2= new Team();
38             team2.setTeamName("team2");
39             
40             Student s1 = new Student();
41             Student s2 = new Student();
42             Student s3 = new Student();
43             Student s4 = new Student();
44             Student s5 = new Student();
45             Student s6 = new Student();
46             
47             s1.setName("zhangsan");
48             s2.setName("lisi");
49             s3.setName("wangwu");
50             s4.setName("zhaoliu");
51             s5.setName("5zhaoliu");
52             s6.setName("6zhaoliu");
53             
54             team.getStudents().add(s1);
55             team.getStudents().add(s2);
56             
57             team2.getStudents().add(s3);
58             team2.getStudents().add(s4);
59             team2.getStudents().add(s5);
60             team2.getStudents().add(s6);
61             
62             session.save(team);
63             session.save(team2);
64             
65             tx.commit();
66         }
67         catch(Exception ex)
68         {
69             if(null != tx)
70             {
71                 tx.rollback();
72             }
73             ex.printStackTrace();
74         }
75         finally
76         {
77             session.close();
78         }
79     }
80 }

Hibernate: insert into team (teamname, id) values (?, ?)

Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into team (teamname, id) values (?, ?)
Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into student (card_id, name, age, team_id, id) values (?, ?, ?, ?, ?)
Hibernate: update student set team_id=?, index_=? where id=?
Hibernate: update student set team_id=?, index_=? where id=?
Hibernate: update student set team_id=?, index_=? where id=?
Hibernate: update student set team_id=?, index_=? where id=?
Hibernate: update student set team_id=?, index_=? where id=?
Hibernate: update student set team_id=?, index_=? where id=?

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原文地址：https://www.cnblogs.com/caoyc/p/5597122.html