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">  </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>  </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 Persondrop table if exists hibernate_unique_keycreate 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 SessionFactorysessionFactory = 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 yetif (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：