Hibernate Map集合映射簡單例子

Map集合的特點就是使用了鍵值對，即Key-Value結構來存放集合元素，這樣就需要對應的集合元素數據庫表中包含對于Key的列。

建兩個相應的表：

email_map:

create table email_map(
id int(11) not null,
email_id varchar(20) not null,
email varchar(100) not null default ''
)engine=innodb default charset=gbk;

user_map:

create table user_map(
id int(11) not null auto_increment,
name varchar(100) not null default '',
primary key(id)
)engine=innodb default charset=gbk;

建立UserMap.java實體類：

package collect.map;

import java.util.HashMap;
import java.util.Map;

public class UserMap implements java.io.Serializable {

    // Fields

    private Integer id;
    private String name;
    private Map emails = new HashMap();

    // Constructors

    /** default constructor */
    public UserMap() {
    }

    /** full constructor */
    public UserMap(String name) {
        this.name = name;
    }

    // Property accessors

    public Integer getId() {
        return this.id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Map getEmails() {
        return emails;
    }

    public void setEmails(Map emails) {
        this.emails = emails;
    }

}

建立映射文件UserMap.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 Persistence Tools
-->
<hibernate-mapping>
    <class name="collect.map.UserMap" table="user_map" catalog="ssh">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" length="100" not-null="true" />
        </property>
        <map name="emails" table="email_map">
            <key column="id"></key>
            <map-key column="email_id" type="java.lang.String"></map-key>
            <element type="java.lang.String" column="email"></element>
        </map>
    </class>
</hibernate-mapping>

注解：其中Map類型映射中<map-key>標簽指明Map使用了String類型作為Key，它配置鍵值對中的“鍵”。這樣經Map類型映射配置后，操作map.put("A","B")中的"A"、"B" 對應表email_map中的字段email_id、email。

將該映射文件加入到Hibernate配置文件中，建立測試類Test.java：

package collect.map;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Test {

    public static void main(String[] args) {
        // Configuration管理Hibernate配置
        Configuration config = new Configuration().configure();
        // 根據Configuration建立 SessionFactory
        // SessionFactory用來建立Session
        SessionFactory sessionFactory = config.buildSessionFactory();

        // 創建實例
        UserMap user1 = new UserMap();
        user1.setName("user1");
        user1.getEmails().put("no.1", "email1");
        user1.getEmails().put("no.2", "email2");

        UserMap user2 = new UserMap();
        user2.setName("user2");
        user2.getEmails().put("no.3", "email3");
        user2.getEmails().put("no.4", "email4");

        // 添加數據
        Session session = sessionFactory.openSession();
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
                        session.save(user1);
            session.save(user2);
            tx.commit();
        } catch (RuntimeException e) {
            if (tx != null)
                tx.rollback();
            throw e;
        } finally {
            session.close();
        }

        // 關閉sessionFactory
        sessionFactory.close();

    }

}

運行結果：

控制臺：

23:10:32,980 DEBUG SQL:346 - insert into ssh.user_map (name) values (?)
23:10:32,997 DEBUG SQL:346 - insert into ssh.user_map (name) values (?)
23:10:33,004 DEBUG SQL:346 - insert into email_map (id, email_id, email) values (?, ?, ?)
23:10:33,007 DEBUG SQL:346 - insert into email_map (id, email_id, email) values (?, ?, ?)
23:10:33,007 DEBUG SQL:346 - insert into email_map (id, email_id, email) values (?, ?, ?)
23:10:33,007 DEBUG SQL:346 - insert into email_map (id, email_id, email) values (?, ?, ?)

注解：從上面日志輸出中可以看到，Key和Value的對應關系。
數據庫：