Hibernate List集合映射簡單例子

建兩個相應的表：

email_list:

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

user_list:

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

package collect.list;

import java.util.ArrayList;
import java.util.List;

public class UserList implements java.io.Serializable {
    // Fields
    private Integer id;
    private String name;
    private List emails = new ArrayList();

    // Constructors
    /** default constructor */
    public UserList() {
    }

    /** full constructor */
    public UserList(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 List getEmails() {
        return emails;
    }

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

    public void addEmail(String email) {
        emails.add(email);
    }

    public void removeEmail(String email) {
        emails.remove(email);
    }
}

<?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.list.UserList" table="user_list" 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>
        <list name="emails" table="email_list">
            <key column="id"></key>
            <index column="email_id"></index>
            <element type="java.lang.String" column="email"></element>
        </list>
    </class>
</hibernate-mapping>

注解：其中List類型映射中<index>標簽指定email_id字段記錄List元素序號。

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

package collect.list;

import java.util.List;
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
        UserList user1 = new UserList();
        user1.setName("user1");
        user1.addEmail("email1");
        user1.addEmail("email2");
        user1.addEmail("email1");
        user1.addEmail("email3");

        UserList user2 = new UserList();
        user2.setName("user2");
        user2.addEmail("email3");
        user2.addEmail("email4");


        // 添加數據
        Session session = sessionFactory.openSession();
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            // INSERT到數據庫
            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();

    }

}

### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### direct messages to file hibernate.log ###
#log4j.appender.file=org.apache.log4j.FileAppender
#log4j.appender.file.File=hibernate.log
#log4j.appender.file.layout=org.apache.log4j.PatternLayout
#log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

#log4j.rootLogger=warn, stdout
log4j.rootLogger=debug, stdout

#log4j.logger.org.hibernate=info
log4j.logger.org.hibernate=warn

### log HQL query parser activity
#log4j.logger.org.hibernate.hql.ast.AST=debug

### log just the SQL
log4j.logger.org.hibernate.SQL=debug

### log JDBC bind parameters ###
#log4j.logger.org.hibernate.type=info
log4j.logger.org.hibernate.type=warn

### log schema export/update ###
log4j.logger.org.hibernate.tool.hbm2ddl=warn

### log HQL parse trees
log4j.logger.org.hibernate.hql=debug

### log cache activity ###
log4j.logger.org.hibernate.cache=debug

### log transaction activity
log4j.logger.org.hibernate.transaction=warn

### log JDBC resource acquisition
log4j.logger.org.hibernate.jdbc=warn

### enable the following line if you want to track down connection ###
### leakages when using DriverManagerConnectionProvider ###
#log4j.logger.org.hibernate.connection.DriverManagerConnectionProvider=trace

運行結果：

控制臺：

22:21:25,196 DEBUG SQL:346 - insert into ssh.user_list (name) values (?)
22:21:25,213 DEBUG SQL:346 - insert into ssh.user_list (name) values (?)
22:21:25,220 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,221 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,221 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,223 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,223 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,224 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)

數據庫：

對比Set集合映射中沒有email_id字段，就是因為Set集合中的元素是無序不重復的，而List集合中元素是有序可重復的。對于Set集合而言，email中重復的記錄會被覆蓋，這樣一來email_id字段就沒有意義了。而對于List集合，email聯合字段email_id才可唯一確定一個有序email，emial_id相當于是List類型映射中<index>標簽的index(索引,從下標0開始)了。