這篇文章主要說的是在Hibernate中的組件（Component）映射，可以參考Hibernate官方文檔的第7章。至於環境設定，可以參考這個系列的前面幾篇文章。 1. 建立項目 · 建立一個Java項目：ComponentMapping，注意選中“建立單獨的源檔案夾和輸出檔案夾”，同時添加“使用者庫”：hibernate。 2. 編寫類檔案 · 建立一個類，包名：javamxj.hibernate.component，類名：Person。
Person.java
/* * Hibernate - 組件（Component）映射 * 建立日期 2005-4-10 * @author javamxj（分享java快樂） * @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類調用了Address類，注意在“getAddress()”方法上的“ @hibernate.component”標記。 · Address類只含有一些“ @hibernate.property”標記，沒有將其獨立映射為一個表。
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+"區" +"\n\t郵遞區號: "+ zipCode);}}
3. 運行任務 · 複製《Eclipse快速上手Hibernate--4. 繼承映射(1)》文中的build.xml到項目目錄下。· 雙擊“generate-hbm”任務，會發現在包中多了一個Animal.hbm.xml檔案，在src目錄下會多了一個hibernate.cfg.xml檔案，如果沒有，按F5鍵重新整理一下。
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>
· 運行MySql伺服器，然後雙擊“schemaexport”任務，在項目根目錄下，會產生一個“schema-export.sql”檔案。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 )
· 切換到資料庫中，會發現已經自動產生了資料表Person 5. 測試程式 ● 這一次不同於前面的幾個執行個體，這次先實現一個HibernateUtil輔助類，用來管理Hibernate的Session，這樣測試類別的代碼就比較簡單了，可以參考Hibernate官方文檔的第1章。 · 建立一個類，包名：javamxj.hibernate.util，類名：HibernateUtil，代碼如下：
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，然後在包javamxj.hibernate.component下建立一個ComponentDemo.java類。
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("中國", "上海", "普陀", "200055"));p.setUsername("JavaMXJ");sess.save(p);p = new Person();p.setAddress(new Address("中國", "北京", "海澱", "100086"));p.setUsername("張三");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();}}
· 運行這個類，控制台輸出如下： · 同時，資料表中產生如下資料： · 最後的項目結構如下：
