<class name="com.yiibai.Question" table="q100">  
       ...        
          <list name="answers" table="ans100">  
          <key column="qid"></key>  
          <index column="type"></index>  
          <element column="answer" type="string"></element>  
          </list>  

       ...  
</class>

注： List 和 Map是基于索引的集合，因此將在表中創(chuàng)建一個(gè)額外的列進(jìn)行索引。

集合映射中的映射列表(List)示例

在這個(gè)例子中，我們將看到列表(List)在集合映射的完整示例。這是List中存儲(chǔ)字符串值而不是實(shí)體引用的示例，這就是為什么要在列表元素中使用element標(biāo)簽而不是one-to-many標(biāo)簽的元素。

這個(gè)示例項(xiàng)目的完整結(jié)構(gòu)如下圖所示 -

1)創(chuàng)建持久化類

這個(gè)持久化類定義了類的屬性，包括List。

package com.yiibai;

import java.util.List;

public class Question {
    private int id;
    private String qname;
    private List<String> answers;

    public int getId() {
        return id;
    }

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

    public String getQname() {
        return qname;
    }

    public void setQname(String qname) {
        this.qname = qname;
    }

    public List<String> getAnswers() {
        return answers;
    }

    public void setAnswers(List<String> answers) {
        this.answers = answers;
    }

}

2)創(chuàng)建持久化類的映射文件

在這里，我們創(chuàng)建了用于定義列表的question.hbm.xml文件。

<?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">

<hibernate-mapping>
    <class name="com.yiibai.Question" table="question_100">
        <id name="id">
            <generator class="increment"></generator>
        </id>
        <property name="qname"></property>

        <list name="answers" table="answer_100">
            <key column="qid"></key>
            <index column="type"></index>
            <element column="answer" type="string"></element>
        </list>

    </class>

</hibernate-mapping>

3)創(chuàng)建配置文件

此文件包含有關(guān)數(shù)據(jù)庫(kù)和映射文件的信息。

文件：hibernate.hnm.xml 內(nèi)容如下 -

<?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="hbm2ddl.auto">update</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/test</property>
        <property name="connection.username">root</property>
        <property name="connection.password">123456</property>
        <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
        <property name="show_sql">true</property>
    <mapping resource="question.hbm.xml"/>
    </session-factory>

</hibernate-configuration>

4)創(chuàng)建存儲(chǔ)數(shù)據(jù)的類

在這個(gè)類(MainTest.java)中，用來(lái)存儲(chǔ)Question類的數(shù)據(jù)。使用HQL來(lái)獲取Answer類的所有記錄，包括答案。在這個(gè)示例中，它從功能相關(guān)的兩個(gè)表中獲取數(shù)據(jù)。

package com.yiibai;

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

import org.hibernate.*;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.*;

public class MainTest {
    public static void main(String[] args) {
        // 但在5.1.0版本匯總，hibernate則采用如下新方式獲取：
        // 1. 配置類型安全的準(zhǔn)服務(wù)注冊(cè)類，這是當(dāng)前應(yīng)用的單例對(duì)象，不作修改，所以聲明為final
        // 在configure("cfg/hibernate.cfg.xml")方法中，如果不指定資源路徑，默認(rèn)在類路徑下尋找名為hibernate.cfg.xml的文件
        final StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
                .configure("hibernate.cfg.xml").build();
        // 2. 根據(jù)服務(wù)注冊(cè)類創(chuàng)建一個(gè)元數(shù)據(jù)資源集，同時(shí)構(gòu)建元數(shù)據(jù)并生成應(yīng)用一般唯一的的session工廠
        SessionFactory sessionFactory = new MetadataSources(registry)
                .buildMetadata().buildSessionFactory();

        /**** 上面是配置準(zhǔn)備，下面開(kāi)始我們的數(shù)據(jù)庫(kù)操作 ******/
        Session session = sessionFactory.openSession();// 從會(huì)話工廠獲取一個(gè)session

        // creating transaction object
        Transaction t = session.beginTransaction();

        ArrayList<String> list1 = new ArrayList<String>();
        list1.add("java is a programming language");
        list1.add("java is a platform");

        ArrayList<String> list2 = new ArrayList<String>();
        list2.add("Servlet is an Interface");
        list2.add("Servlet is an API");

        Question question1 = new Question();
        question1.setQname("Java 是什么?");
        question1.setAnswers(list1);

        Question question2 = new Question();
        question2.setQname("Hibernate 是什么?");
        question2.setAnswers(list2);

        session.persist(question1);
        session.persist(question2);

        t.commit();

        // 查詢數(shù)據(jù)
        Query<Question> query = session.createQuery("from Question");
        List<Question> list = query.list();

        Iterator<Question> itr = list.iterator();
        while (itr.hasNext()) {
            Question q = itr.next();
            System.out.println("Question Name: " + q.getQname());

            // printing answers
            List<String> list21 = q.getAnswers();
            Iterator<String> itr2 = list21.iterator();
            while (itr2.hasNext()) {
                System.out.println(itr2.next());
            }

        }
        session.close();
        System.out.println("success");

    }
}

執(zhí)行上面代碼，得到以下輸出結(jié)果 -

log4j:WARN No appenders could be found for logger (org.jboss.logging).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Sun Mar 26 05:18:56 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Hibernate: select max(id) from question_100
Hibernate: insert into question_100 (qname, id) values (?, ?)
Hibernate: insert into question_100 (qname, id) values (?, ?)
Hibernate: insert into answer_100 (qid, type, answer) values (?, ?, ?)
Hibernate: insert into answer_100 (qid, type, answer) values (?, ?, ?)
Hibernate: insert into answer_100 (qid, type, answer) values (?, ?, ?)
Hibernate: insert into answer_100 (qid, type, answer) values (?, ?, ?)
Hibernate: select question0_.id as id1_1_, question0_.qname as qname2_1_ from question_100 question0_
Question Name: What is Java?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
java is a programming language
java is a platform
Question Name: What is Servlet?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
Servlet is an Interface
Servlet is an API
Question Name: What is Java?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
java is a programming language
java is a platform
Question Name: What is Servlet?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
Servlet is an Interface
Servlet is an API
Question Name: What is Java?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
java is a programming language
java is a platform
Question Name: What is Servlet?
Hibernate: select answers0_.qid as qid1_0_0_, answers0_.answer as answer3_0_0_, answers0_.type as type2_0_ from answer_100 answers0_ where answers0_.qid=?
Servlet is an Interface
Servlet is an API
Question Name: Java 是什么?
java is a programming language
java is a platform
Question Name: Hibernate 是什么?
Servlet is an Interface
Servlet is an API
success

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