5.6.4 映射集合属性:Map集合属性

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我们先将test库里的表删除：

然后新建一个web工程，并编写代码：

Person.java :

public class Person {private int id;private String name;private int age;private Map<String,Float> scores=new HashMap<String,Float>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public Map<String, Float> getScores() {return scores;}public void setScores(Map<String, Float> scores) {this.scores = scores;}}

Person.hbm.xml :

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">    <hibernate-mapping package="db.domain">    <class name="Person" table="persons">            <id name="id" type="integer">            <generator class="native"></generator>        </id>        <property name="name" type="string">            <column name="name"></column>        </property>        <property name="age" type="integer">            <column name="age"></column>        </property>        <map name="scores" table="scores">            <key column="person_id" not-null="true"/>            <map-key column="subject" type="string"></map-key>            <element column="grade" type="float"/>        </map>            </class></hibernate-mapping>

Map集合属性需要使用<map.../>元素进行映射。当配置<map.../>元素时也需要使用<key.../>子元素映射外键列。除此之外，Map集合属性还需要映射Map key。映射Map集合key的元素比较多，当Map的key是字符串类型或日期类型时，直接使用<map-key.../>元素来映射Map key即可。Hibernate将以外键列和key列作为联合主键。

Test.java :

public class Test {public static void main(String[] args) {Person p1=new Person();p1.setName("tom");p1.setAge(10);Map<String,Float> map1=new HashMap<String,Float>();map1.put("语文",85.5f);map1.put("数学",95.0f);p1.setScores(map1);Person p2=new Person();p2.setName("jack");p2.setAge(15);Map<String,Float> map2=new HashMap<String,Float>();map2.put("语文",85.5f);map2.put("数学",95.0f);map2.put("英语",93.5f);p2.setScores(map2);Session session=HibernateSessionFactory.getSession();Transaction txt=session.beginTransaction();session.save(p1);session.save(p2);txt.commit();HibernateSessionFactory.closeSession();}}

运行Test.java，查看数据库：