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>
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