dljd_(062-065)_hibernate关联关系映射_单向关联

一、一对多关联关系映射(单向关联)

　　一个国家(Contry)有多个部长(Minister)

　　1.1定义Country实体类及其到数据库之间的映射(Country.hbm.xml)

package edu.aeon.beans;

import java.util.Set;

/**
 * [说明]:Country(国家)实体类
 * @author aeon
 *
 */
public class Country {
    /**国家id*/
    private Integer cid;
    /**国家名*/
    private String cname;
    /**一个国家里部长集合*/
    private Set<Minister> ministers;
    public Country() {
        super();
    }
    public Country(String cname) {
        super();
        this.cname = cname;
    }

    public Integer getCid() {
        return cid;
    }
    public void setCid(Integer cid) {
        this.cid = cid;
    }
    public String getCname() {
        return cname;
    }
    public void setCname(String cname) {
        this.cname = cname;
    }
    public Set<Minister> getMinisters() {
        return ministers;
    }
    public void setMinisters(Set<Minister> ministers) {
        this.ministers = ministers;
    }
    @Override
    public String toString() {
        return "Country [cid=" + cid + ", cname=" + cname + ", minister=" + ministers + "]";
    }
}

Country.hbm.xml如下：　　

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="edu.aeon.beans">
    <class name="Country">
        <id name="cid">
            <column name="cid" sql-type="int(3)"/>
            <generator class="native"/>
        </id>
        <property name="cname">
            <column name="cname" sql-type="varchar(16)"/>
        </property>
        <!-- 关联属性的映射配置 -->
        <!-- name:关联属性的属性名 -->
        <set name="ministers">
            <!-- 关联的外键 -->
            <key column="countryid" />
            <!-- 关联到那个类 -->
            <one-to-many class="Minister"/>
        </set>
    </class>
</hibernate-mapping>

　　1.2定义Minister实体类及其到数据库之间的映射(Minister.hbm.xml)　

package edu.aeon.beans;
/**
 * [说明]:minister(部长)实体类
 * @author aeon
 *
 */
public class Minister {
    /**部长id*/
    private Integer mid;
    /**部长名*/
    private String mname;
    public Minister() {

    }
    public Minister(String mname) {
        super();
        this.mname = mname;
    }
    
    public Integer getMid() {
        return mid;
    }
    public void setMid(Integer mid) {
        this.mid = mid;
    }
    public String getMname() {
        return mname;
    }
    public void setMname(String mname) {
        this.mname = mname;
    }
    @Override
    public String toString() {
        return "Minister [mid=" + mid + ", mname=" + mname + "]";
    }
}

Minister.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="edu.aeon.beans">
    <class name="Minister">
        <id name="mid">
            <column name="mid" sql-type="int(3)"/>
            <generator class="native"/>
        </id>
        <property name="mname">
            <column name="mname" sql-type="varchar(16)"/>
        </property>
    </class>
</hibernate-mapping>

　　1.3然后将Country.hbm.xml和Minister.hbm.xml注册到主配置文件中

　　

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 配置数据库的四要素 -->
        <property name="hibernate.connection.driver">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/db_test</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <!-- 配置数据库方言 -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <!-- 配置数据库连接池 -->
        <!-- <property name="hibernate.connection.provider_class">org.hibernate.c3p0.internal.C3P0ConnectionProvider</property> -->
        <!-- 注册当前session上下文 -->
        <property name="hibernate.current_session_context_class">thread</property>
        <!-- 自动建表 -->
        <property name="hibernate.hbm2ddl.auto">update</property>
        <!-- 显示sql -->
        <property name="hibernate.show_sql">true</property>
        <!-- 格式化sql -->
        <property name="hibernate.format_sql">true</property>
        <mapping resource="edu/aeon/beans/Country.hbm.xml"/>
        <mapping resource="edu/aeon/beans/Minister.hbm.xml"/>
        <!-- <mapping resource="sqlMapping.xml"/> -->
    </session-factory>
</hibernate-configuration>    

　　1.4测试类

　　

package edu.aeon.hibernate.test;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import edu.aeon.aeonutils.hibernate.getsessionutil.GetSessionUtil;
import edu.aeon.beans.Country;
import edu.aeon.beans.Minister;

/**
 * [说明]:测试类
 * @author aeon
 *
 */
public class HibernateTest {
    /**
     * 测试1对多关联关系
     */
    @Test
    public  void testOne2Many(){
        Session session=null;
        Transaction transaction=null;
        try {
            session = GetSessionUtil.getSession();
            System.out.println(session);
            transaction = session.getTransaction();
            System.out.println(transaction);
            transaction.begin();
            //操作
            Minister minister1=new Minister("部长甲");
            Minister minister2=new Minister("部长乙");
            Set<Minister> ministers=new HashSet<Minister>();
            ministers.add(minister1);
            ministers.add(minister2);
            Country country=new Country("china");
            country.setMinisters(ministers);
            session.save(minister1);
            session.save(minister2);
            session.save(country);
            transaction.commit();
        } catch (Exception e) {
            transaction.rollback();
            e.printStackTrace();
        }
    }
}

执行结果：　　

Hibernate: 
    
    create table Country (
        cid int(3) not null auto_increment,
        cname varchar(16),
        primary key (cid)
    )
Hibernate: 
    
    create table Minister (
        mid int(3) not null auto_increment,
        mname varchar(16),
        countryid integer,
        primary key (mid)
    )
Hibernate: 
    
    alter table Minister 
        add constraint FKc9dntt9ob26y2m3b5ydae4dva 
        foreign key (countryid) 
        references Country (cid)
ThreadLocalSessionContext.TransactionProtectionWrapper[SessionImpl(PersistenceContext[entityKeys=[],collectionKeys=[]];ActionQueue[insertions=ExecutableList{size=0} updates=ExecutableList{size=0} deletions=ExecutableList{size=0} orphanRemovals=ExecutableList{size=0} collectionCreations=ExecutableList{size=0} collectionRemovals=ExecutableList{size=0} collectionUpdates=ExecutableList{size=0} collectionQueuedOps=ExecutableList{size=0} unresolvedInsertDependencies=null])]
org.hibernate.engine.transaction.internal.TransactionImpl@714c7f58
Hibernate: 
    insert 
    into
        Minister
        (mname) 
    values
        (?)
Hibernate: 
    insert 
    into
        Minister
        (mname) 
    values
        (?)
Hibernate: 
    insert 
    into
        Country
        (cname) 
    values
        (?)
Hibernate: 
    update
        Minister 
    set
        countryid=? 
    where
        mid=?
Hibernate: 
    update
        Minister 
    set
        countryid=? 
    where
        mid=?

执行结果截图：

　　

此时数据库信息截图如下：

　　

 ______________________________________________one2many最终版整理如下__________________________________________________________

package edu.aeon.beans;

import java.util.HashSet;
import java.util.Set;

/**
 * [说明]:Country(国家)实体类
 * @author aeon
 *
 */
public class Country {
    /**国家id*/
    private Integer cid;
    /**国家名*/
    private String cname;
    /**一个国家里部长集合*/
    private Set<Minister> ministers;
    public Country() {
        super();
        //初始化
        ministers=new HashSet<Minister>();
    }
    public Country(String cname) {
        this();
        this.cname = cname;
    }

    public Integer getCid() {
        return cid;
    }
    public void setCid(Integer cid) {
        this.cid = cid;
    }
    public String getCname() {
        return cname;
    }
    public void setCname(String cname) {
        this.cname = cname;
    }
    public Set<Minister> getMinisters() {
        return ministers;
    }
    public void setMinisters(Set<Minister> ministers) {
        this.ministers = ministers;
    }
    @Override
    public String toString() {
        return "Country [cid=" + cid + ", cname=" + cname + ", minister=" + ministers + "]";
    }
}

Country.hbm.xml设置级联方式

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="edu.aeon.beans">
    <class name="Country">
        <id name="cid">
            <column name="cid" sql-type="int(3)"/>
            <generator class="native"/>
        </id>
        <property name="cname">
            <column name="cname" sql-type="varchar(16)"/>
        </property>
        <!-- 关联属性的映射配置 -->
        <!-- name:关联属性的属性名 -->
        <set name="ministers" cascade="save-update">
            <!-- 关联的外键 -->
            <key column="countryid" />
            <!-- 关联到那个类 -->
            <one-to-many class="Minister"/>
        </set>
    </class>
</hibernate-mapping>

测试类：

　　

package edu.aeon.hibernate.test;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import edu.aeon.aeonutils.hibernate.getsessionutil.GetSessionUtil;
import edu.aeon.beans.Country;
import edu.aeon.beans.Minister;

/**
 * [说明]:测试类
 * @author aeon
 *
 */
public class HibernateTest {
    /**
     * 测试1对多关联关系
     */
    @Test
    public  void testOne2Many(){
        Session session=null;
        Transaction transaction=null;
        try {
            session = GetSessionUtil.getSession();
            System.out.println(session);
            transaction = session.getTransaction();
            System.out.println(transaction);
            transaction.begin();
            //操作
            Minister minister1=new Minister("部长甲");
            Minister minister2=new Minister("部长乙");
            Country country=new Country("china");
            country.getMinisters().add(minister1);
            country.getMinisters().add(minister2);
            session.save(country);
            transaction.commit();
        } catch (Exception e) {
            transaction.rollback();
            e.printStackTrace();
        }
    }
}

其它一律保持不变、测试结果同上。

本次程序用到了前面写的一个获取session和sessionFactory的工具类：

　　

package edu.aeon.aeonutils.hibernate.getsessionutil;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
 * [说明]:获取session的工具类
 * @author aeon
 */
public class GetSessionUtil {
    private static SessionFactory sessionFactory;

    /**
     * session获取的第一种写法
     * 由于SessionFactory是一个重量级的对象、这样写没获取一次session都要相应的创建一次SessionFactory对象
     * 创建与销毁时系统开销大、所以不建议使用
     * @return
    public static Session getSession(){//最好别用
        return new Configuration().configure().buildSessionFactory().getCurrentSession();
    }
    */
    /**
     * 通过session工厂获取session
     * @return
     */
    public static Session getSession(){
        return getSessionFactory().getCurrentSession();
    }
    /**
     * 通过配置文件中的配置的session工厂项来实例化session工厂
     * @return
     */
    public static SessionFactory getSessionFactory() {
        if(null==sessionFactory||sessionFactory.isClosed()){
            sessionFactory=new Configuration().configure().buildSessionFactory();
        }
        return sessionFactory;
    }
    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        System.out.println(GetSessionUtil.getSessionFactory()==GetSessionUtil.getSessionFactory());//结果true                        
        System.out.println(GetSessionUtil.getSession()==GetSessionUtil.getSession());//结果true                        
        System.out.println(GetSessionUtil.getSessionFactory().getCurrentSession()==GetSessionUtil.getSession());//结果true                    
    }
}