Hibernate集合映射之Map-----element映射实体类
系统
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在使用map集合配置实体类型时候,其key为某一个字段,而value是这一个实体的实例
比如Team和Student一对多的关系,Team中有一个ma存放student,这个map的key为student中的cardid,而value是具体的一个student实例
需要注意的是,这样使用时候,team端需要维护cardid,所以,不能再像set那样可以在1端设置inverse="true"来提高性能
数据库结构:
create
table
teamMapC (id
varchar
(
32
),teamname
varchar
(
32
));
create
table
studentMapC (id
varchar
(
32
),cardid
varchar
(
32
),name
varchar
(
32
),age
int
,description
varchar
(
32
), team_id
varchar
(
32
));
实体类:
package
Collection.Map.Complex;
public
class
Student
...
{
private
String id;
private
String name;
private
String description;
private
int
age;
private
String cardid;
private
Team team;
public
String getId()
...
{
return
id;
}
public
void
setId(String id)
...
{
this
.id
=
id;
}
public
String getName()
...
{
return
name;
}
public
void
setName(String name)
...
{
this
.name
=
name;
}
public
String getDescription()
...
{
return
description;
}
public
void
setDescription(String description)
...
{
this
.description
=
description;
}
public
int
getAge()
...
{
return
age;
}
public
void
setAge(
int
age)
...
{
this
.age
=
age;
}
public
String getCardid()
...
{
return
cardid;
}
public
void
setCardid(String cardid)
...
{
this
.cardid
=
cardid;
}
public
Team getTeam()
...
{
return
team;
}
public
void
setTeam(Team team)
...
{
this
.team
=
team;
}
}
package
Collection.Map.Complex;
import
java.util.HashMap;
import
java.util.Map;
public
class
Team
...
{
private
String id;
private
String teamname;
private
Map students
=
new
HashMap();
public
String getId()
...
{
return
id;
}
public
void
setId(String id)
...
{
this
.id
=
id;
}
public
String getTeamname()
...
{
return
teamname;
}
public
void
setTeamname(String teamname)
...
{
this
.teamname
=
teamname;
}
public
Map getStudents()
...
{
return
students;
}
public
void
setStudents(Map students)
...
{
this
.students
=
students;
}
}
Hibernate.cfg.xml
<?
xml version='1.0' encoding='UTF-8'
?>
<!
DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"
>
<!--
Generated by MyEclipse Hibernate Tools.
-->
<
hibernate-configuration
>
<
session-factory
>
<
property
name
="connection.username"
>
root
</
property
>
<
property
name
="connection.url"
>
jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312
&
useUnicode=true
</
property
>
<
property
name
="dialect"
>
org.hibernate.dialect.MySQLDialect
</
property
>
<
property
name
="myeclipse.connection.profile"
>
mysql
</
property
>
<
property
name
="connection.password"
>
1234
</
property
>
<
property
name
="connection.driver_class"
>
com.mysql.jdbc.Driver
</
property
>
<
property
name
="hibernate.dialect"
>
org.hibernate.dialect.MySQLDialect
</
property
>
<
property
name
="hibernate.show_sql"
>
true
</
property
>
<
property
name
="current_session_context_class"
>
thread
</
property
>
<
property
name
="jdbc.batch_size"
>
15
</
property
>
<
mapping
resource
="Collection/Map/Complex/Student.hbm.xml"
/>
<
mapping
resource
="Collection/Map/Complex/Team.hbm.xml"
/>
</
session-factory
>
</
hibernate-configuration
>
Team.hbm.xml
<?
xml version="1.0" encoding="utf-8"
?>
<!
DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"
>
<!--
Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<
hibernate-mapping
>
<
class
name
="Collection.Map.Complex.Team"
table
="teamMapC"
>
<
id
name
="id"
unsaved-value
="null"
>
<
generator
class
="uuid.hex"
></
generator
>
</
id
>
<
property
name
="teamname"
type
="string"
column
="teamname"
></
property
>
<!--
由于cardid需要team来维护,所以,使用map表示1对多时候,不能再1方设置inverse="true"
-->
<
map
name
="students"
table
="studentMap"
cascade
="all"
>
<
key
column
="team_id"
></
key
>
<!--
index代表key,element(或one-to-many)代表value
-->
<!--
这里用cardid作为key,具体的student实例作为value
-->
<
index
column
="cardid"
type
="string"
></
index
>
<
one-to-many
class
="Collection.Map.Complex.Student"
/>
</
map
>
</
class
>
</
hibernate-mapping
>
Student.hbm.xml
<?
xml version="1.0" encoding="utf-8"
?>
<!
DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"
>
<!--
Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<
hibernate-mapping
>
<
class
name
="Collection.Map.Complex.Student"
table
="studentMapC"
>
<
id
name
="id"
unsaved-value
="null"
>
<
generator
class
="uuid.hex"
></
generator
>
</
id
>
Hibernate集合映射之Map-----element映射实体类型值
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