Eclipse快速上手Hibernate--5. 组件映射

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这篇文章主要说的是在Hibernate中的组件（Component）映射，可以参考Hibernate官方文档的第7章。至于环境设置，可以参考这个系列的前面几篇文章。

1. 创建项目

· 新建一个Java项目：ComponentMapping，注意选中“创建单独的源文件夹和输出文件夹”，同时添加“用户库”：hibernate。

2. 编写类文件

· 新建一个类，包名：javamxj.hibernate.component，类名：Person。

Person.java

/*
 * Hibernate - 组件（Component）映射
 * 创建日期 2005-4-10
 * @author javamxj（分享java快乐）
 * @link  Blog: htpp://javamxj.mblogger.cn  
 *              htpp://blog.csdn.net/javamxj/ 
 */
package javamxj.hibernate.component;
/**
 * @hibernate.class
 */
public class Person {
	private Long id;
	private String username;
	private Address address;
	
	/**
	 * @hibernate.id 
	 *	generator-class="hilo" 
	 *	unsaved-value="null"
	 */
	public Long getId() {return id;}
	public void setId(Long id) {this.id = id;}
	
	/**
	 * @hibernate.property 
	 * 	length="15"
	 *  unique="true"
	 * 	not-null="true"
	 */
	public String getUsername() {return username;}
	public void setUsername(String username) {this.username = username;}
	
	/**
	 * @hibernate.component
	 */
	public Address getAddress() {return address;}
	public void setAddress(Address address) {this.address = address;}
}

· Person类调用了Address类，注意在“getAddress()”方法上的“ @hibernate.component”标记。

· Address类只含有一些“ @hibernate.property”标记，没有将其独立映射为一个表。

Address.java

package javamxj.hibernate.component;

public class Address {
	private String country;
	private String city;
	private String street;
	private String zipCode;
	
	public Address() {}
	public Address(String country, String city, String street, String zipcode) {
		super();
		this.country = country;
		this.city = city;
		this.street = street;
		this.zipCode = zipcode;
	}

	/**
	 * @hibernate.property
	 *  length = "12"
	 */
	public String getCity() {return city;}
	public void setCity(String city) {this.city = city;}
	
	/**
	 * @hibernate.property
	 *  length = "12"
	 */
	public String getCountry() {return country;}
	public void setCountry(String country) {this.country = country;}
	
	/**
	 * @hibernate.property
	 *  length = "6"
	 */
	public String getZipCode() {return zipCode;}
	public void setZipCode(String number) {this.zipCode = number;}
	
	/**
	 * @hibernate.property
	 *  length = "12"
	 */
	public String getStreet() {return street;}
	public void setStreet(String street) {this.street = street;}
	
	public String toString(){
		return ("居住在"+ country + city+"市"+ street+"区"
			  +	"\n\t邮政编码: "+ zipCode);
	}

}

3. 运行任务

· 复制《Eclipse快速上手Hibernate--4. 继承映射(1)》文中的build.xml到项目目录下。

· 双击“generate-hbm”任务，会发现在包中多了一个Animal.hbm.xml文件，在src目录下会多了一个hibernate.cfg.xml文件，如果没有，按F5键刷新一下。

Person.hbm.xml

<?xml version="1.0" encoding="GBK"?>

<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 2.0//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping
>
    <class
        name="javamxj.hibernate.component.Person"
        dynamic-update="false"
        dynamic-insert="false"
        select-before-update="false"
        optimistic-lock="version"
    >

        <id
            name="id"
            column="id"
            type="java.lang.Long"
            unsaved-value="null"
        >
            <generator class="hilo">
              <!--  
                  To add non XDoclet generator parameters, create a file named 
                  hibernate-generator-params-Person.xml 
                  containing the additional parameters and place it in your merge dir. 
              --> 
            </generator>
        </id>

        <property
            name="username"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="username"
            length="15"
            not-null="true"
            unique="true"
        />

        <component
            name="address"
            class="javamxj.hibernate.component.Address"
        >
        <property
            name="city"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="city"
            length="12"
        />

        <property
            name="country"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="country"
            length="12"
        />

        <property
            name="zipCode"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="zipCode"
            length="6"
        />

        <property
            name="street"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="street"
            length="12"
        />

        </component>

        <!--
            To add non XDoclet property mappings, create a file named
                hibernate-properties-Person.xml
            containing the additional properties and place it in your merge dir.
        -->

    </class>

</hibernate-mapping>

· 运行MySql服务器，然后双击“schemaexport”任务，在项目根目录下，会产生一个“schema-export.sql”文件。

schema-export.sql

            drop table if exists Person
drop table if exists hibernate_unique_key
create table Person (
   id bigint not null,
   username varchar(15) not null unique,
   city varchar(12),
   country varchar(12),
   zipCode varchar(6),
   street varchar(12),
   primary key (id)
)
create table hibernate_unique_key (
    next_hi integer 
)
insert into hibernate_unique_key values ( 0 )
            

· 切换到数据库中，会发现已经自动产生了数据表Person

5. 测试程序

● 这一次不同于前面的几个实例，这次先实现一个HibernateUtil辅助类，用来管理Hibernate的Session，这样测试类的代码就比较简单了，可以参考Hibernate官方文档的第1章。

· 新建一个类，包名：javamxj.hibernate.util，类名：HibernateUtil，代码如下：

HibernateUtil.java

package javamxj.hibernate.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;
import net.sf.hibernate.cfg.Configuration;

public class HibernateUtil {

	private static Log log = LogFactory.getLog(HibernateUtil.class);

	private static SessionFactory sessionFactory;

	private static final ThreadLocal threadSession = new ThreadLocal();

	private static final ThreadLocal threadTransaction = new ThreadLocal();

	public static SessionFactory getSessionFactory() {
		if (sessionFactory == null) {
			try {
				// Create the SessionFactory
				sessionFactory = new Configuration().configure()
						.buildSessionFactory();
			} catch (HibernateException ex) {
				ex.printStackTrace();
				throw new RuntimeException("Configuration problem: "
						+ ex.getMessage(), ex);
			}
		}
		return sessionFactory;
	}

	public static Session currentSession() throws HibernateException {
		Session s = (Session) threadSession.get();
		// Open a new Session, if this Thread has none yet
		if (s == null) {
			s = getSessionFactory().openSession();
			log.debug("###Opening new Session for this thread:" + s);
			threadSession.set(s);
		} else {
			log.debug("###Session was existed:" + s);
		}
		return s;
	}

	public static void closeSession() throws HibernateException {
		Session s = (Session) threadSession.get();
		threadSession.set(null);
		if (s != null) {
			log.debug("###Closing Session of this thread. " + s);
			s.close();
		}
	}

	public static void beginTransaction() throws HibernateException {
		Transaction tx = (Transaction) threadTransaction.get();
		try {
			if (tx == null) {
				tx = currentSession().beginTransaction();
				log.debug("###Starting new database transaction in this thread:"+ tx);
				threadTransaction.set(tx);
			} else {
				log.debug("###Tx was existed:" + tx);
			}
		} catch (HibernateException ex) {
			throw ex;
		}
	}

	public static void commitTransaction() throws HibernateException {
		Transaction tx = (Transaction) threadTransaction.get();
		try {
			if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack()) {
				log.debug("###Committing database transaction of this thread.");
				tx.commit();
			}
			threadTransaction.set(null);
		} catch (HibernateException ex) {
			rollbackTransaction();
			throw ex;
		}
	}

	public static void rollbackTransaction() throws HibernateException {
		Transaction tx = (Transaction) threadTransaction.get();
		try {
			threadTransaction.set(null);
			if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack()) {
				log.debug("###Tyring to rollback database transaction of this thread.");
				tx.rollback();
			}
		} catch (HibernateException ex) {
			throw ex;
		} finally {
			closeSession();
		}
	}

}

· 好了，然后在包javamxj.hibernate.component下新建一个ComponentDemo.java类。

ComponentDemo.java

package javamxj.hibernate.component;

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

import javamxj.hibernate.util.HibernateUtil;


import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;

public class ComponentDemo {
	public static void main(String[] args) {
		try {
			new ComponentDemo();
		} catch (HibernateException he) {
			he.printStackTrace();
		}
	}

	public ComponentDemo() throws HibernateException {

		Session sess = HibernateUtil.currentSession();

		Person p = new Person();
		p.setAddress(new Address("中国", "上海", "普陀", "200055"));
		p.setUsername("JavaMXJ");
		sess.save(p);

		p = new Person();
		p.setAddress(new Address("中国", "北京", "海淀", "100086"));
		p.setUsername("张三");
		sess.save(p);

		List animals = sess.find("from " + Person.class.getName());
		for (Iterator it = animals.iterator(); it.hasNext();) {
			Person person = (Person) it.next();
			System.out.println(person.getUsername() + ":" + person.getAddress());
		}
		
		HibernateUtil.closeSession();

	}
}

· 运行这个类，控制台输出如下：

· 同时，数据表中生成如下数据：

· 最后的项目结构如下：