Eclipse快速上手Hibernate--5. 组件映射

答案：    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 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

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