摘要：此為我給公司內(nèi)部新員工培訓(xùn)的實(shí)戰(zhàn)演示例子，傻瓜級(jí)教程，講述了開(kāi)發(fā)中的注意要點(diǎn)和常見(jiàn)錯(cuò)誤，目的主要是讓他們適應(yīng)企業(yè)級(jí)快速流水作業(yè)。由于是面對(duì)面講解，所以沒(méi)有詳細(xì)的文檔，現(xiàn)在簡(jiǎn)單整理如下，希望對(duì)入門(mén)者有幫助。
培訓(xùn)的目標(biāo)：對(duì)下面的開(kāi)發(fā)過(guò)程和模式快速理解和應(yīng)用。基于我的UML架構(gòu)-----〉Java POJOs代碼------〉在pojos中做xdoclet標(biāo)識(shí)-------〉基于ant生成*.hbm.xml文件（借助于eclipse可以自動(dòng)化配置）------〉生成database schma和數(shù)據(jù)庫(kù)sql語(yǔ)句。逐步可以讓新員工過(guò)渡到java5的annotation來(lái)開(kāi)發(fā)EJB3 .
基于主鍵的一對(duì)一關(guān)聯(lián)映射
說(shuō)明：下面是我們用到的例子，學(xué)生和自己學(xué)籍上的照片是一對(duì)一關(guān)系。下面是使用IBM RSA得到的一個(gè)模型，途中用的是兩個(gè)用途，表示的意思比較泛，最佳表示應(yīng)該是一條無(wú)方向的線段，兩邊各標(biāo)上1，代表一對(duì)一關(guān)系。（現(xiàn)在時(shí)間比較緊，所以沒(méi)來(lái)的急修改，這也是IBM反向工程的一個(gè)弱點(diǎn)，就好比目標(biāo)是北京，但是現(xiàn)在目標(biāo)指向了中國(guó)，不夠精確,但是可以反映這個(gè)意思）
下面是生成的數(shù)據(jù)庫(kù)E-R圖：
問(wèn)題：初學(xué)者總是對(duì)pojos對(duì)象中的字段和數(shù)據(jù)庫(kù)中的字段做對(duì)比，對(duì)pojos對(duì)象中多出的propertity感到不解，其實(shí)這也是hibernate的關(guān)鍵所在，在那個(gè)表增加字段，增加外鍵，都是有規(guī)律的，也是完全符合數(shù)據(jù)庫(kù)的規(guī)則的，詳細(xì)看代碼.
初學(xué)者應(yīng)該注意點(diǎn)，需要自己進(jìn)行實(shí)踐的操作：
1， /**
* @hibernate.class table = "image" schema = "hibernate_tutorial"
* @author Administrator
*
*/
schema對(duì)mysql數(shù)據(jù)庫(kù)來(lái)說(shuō)，是數(shù)據(jù)庫(kù)名字，這點(diǎn)注意
2， 你可以在關(guān)聯(lián)屬性上都定義外鍵，你看一下最后那邊的設(shè)置在數(shù)據(jù)庫(kù)sql語(yǔ)句中體現(xiàn)了，那個(gè)沒(méi)體現(xiàn)，我想你會(huì)有收獲的。
3， /**
* @hibernate.one-to-one class = "com.javawebside.one2one.p1.Image"
* constrained = "false" outer-join = "true" cascade="all"
* @return Returns the image.
*/
注意cascade的設(shè)置，如果沒(méi)有級(jí)聯(lián)，那么你可以最后save student,或者save image，或者，兩者都保存，你看一下數(shù)據(jù)庫(kù)中實(shí)際存入的數(shù)據(jù)，你一定會(huì)對(duì)cascade有更加深入的認(rèn)識(shí)。
Image類(lèi)
package com.javawebside.one2one.p1;
import java.sql.Blob;
/**
* @hibernate.class table = "image" schema = "hibernate_tutorial"
* @author Administrator
*
*/
public class Image {
private Long id;
private String name;
private Blob value = null;
/**
* @link association
*/
private Student student;
public Image(){}
public Image(Long id, String name, Blob value) {
super();
this.id = id;
this.name = name;
this.value = value;
}
/**
* @hibernate.id column = "id" generator-class = "foreign"
* @hibernate.generator-param name = "property" value = "student"
* @return Returns the id.
*/
public Long getId() {
return id;
}
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
/**
* @hibernate.property column = "name" not-null = "false" unique = "false"
* @return Returns the name.
*/
public String getName() {
return name;
}
/**
* @param name
* The name to set.
*/
public void setName(String name) {
this.name = name;
}
/**
* @hibernate.property column = "value" not-null = "false" unique = "false"
* @return Returns the value.
*/
public Blob getValue() {
return value;
}
/**
* @param value
* The value to set.
*/
public void setValue(Blob value) {
this.value = value;
}
/**
* @hibernate.one-to-one class = "com.javawebside.one2one.p1.Student" constrained = "true"
* foreign-key="forein_key_name"
* @return
*/
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
}
Student類(lèi)
package com.javawebside.one2one.p1;
/**
*
* @hibernate.class table = "student" schema = "hibernate_tutorial"
* @author Administrator
*
*/
public class Student {
private Long id;
private String name;
private String intro;
private Image image;
public Student() {
}
public Student(Long id, String name, String intro, Image image) {
super();
this.id = id;
this.name = name;
this.intro = intro;
this.image = image;
}
/**
* @hibernate.id column = "id" generator-class = "native"
* @return Returns the id.
*/
public Long getId() {
return id;
}
/**
* @param id
* The id to set.
*/
public void setId(Long id) {
this.id = id;
}
/**
* @hibernate.property column = "intro" not-null = "false" unique = "false"
* @return Returns the intro.
*/
public String getIntro() {
return intro;
}
/**
* @param intro
* The intro to set.
*/
public void setIntro(String intro) {
this.intro = intro;
}
/**
* @hibernate.property column = "name" not-null = "false" unique = "false"
* @return Returns the name.
*/
public String getName() {
return name;
}
/**
* @param name
* The name to set.
*/
public void setName(String name) {
this.name = name;
}
/**
* @hibernate.one-to-one class = "com.javawebside.one2one.p1.Image"
* constrained = "false" outer-join = "true" cascade="all"
* @return Returns the image.
*/
public Image getImage() {
return image;
}
/**
* @param image
* The image to set.
*/
public void setImage(Image image) {
this.image = image;
}
}
下面是實(shí)際的操作類(lèi)
BusinessService類(lèi)用于增加和刪除數(shù)據(jù)操作
package com.javawebside.one2one.p1;
import java.sql.Blob;
import org.hibernate.*;
//import org.hibernate.cfg.Configuration;
//import java.util.*;
public class BusinessService {
private Session session;
public void setSession(Session se) {
session = se;
}
public Session getSession() {
return session;
}
public void saveStudent(Student Student) throws Exception {
Transaction tx = null;
try {
tx = session.beginTransaction();
session.save(Student);
tx.commit();
} catch (Exception e) {
if (tx != null) {
tx.rollback();
}
throw e;
} finally {
// No matter what, close the session
session.close();
}
}
public Student loadStudent(Long id) throws Exception {
Transaction tx = null;
try {
tx = session.beginTransaction();
Student Student = (Student) session.load(Student.class, id);
tx.commit();
return Student;
} catch (Exception e) {
if (tx != null) {
tx.rollback();
}
throw e;
} finally {
// No matter what, close the session
session.close();
}
}
public void printStudent(Student Student) throws Exception {
Image image = Student.getImage();
System.out.println("Image of " + Student.getName() + " is: "
+ image.getValue());
if (image.getStudent() == null)
System.out.println("Can not naviagte from Image to Student.");
}
public void test() throws Exception {
Student student = new Student();
Image image = new Image();
image.setName("王東照片");
student.setName("Tom");
student.setIntro("王東");
image.setStudent(student);
student.setImage(image);
saveStudent(student);
// student=loadStudent(student.getId());
// printStudent(student);
}
public static void main(String args[]) throws Exception {
BusinessService bs = new BusinessService();
bs.setSession(HibernateSessionFactory.currentSession());
if (bs.getSession() == null)
System.out.println("Session is null");
bs.test();
//bs.getSession().close();
}
}
hibernate配置類(lèi)
package com.javawebside.one2one.p1;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
/**
* Configures and provides access to Hibernate sessions, tied to the
* current thread of execution. Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.html}.
*/
public class HibernateSessionFactory {
/**
* Location of hibernate.cfg.xml file.
* NOTICE: Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file. That
* is place the config file in a Java package - the default location
* is the default Java package.<br><br>
* Examples: <br>
* <code>CONFIG_FILE_LOCATION = "/hibernate.conf.xml".
* CONFIG_FILE_LOCATION = "/com/foo/bar/myhiberstuff.conf.xml".</code>
*/
private static String CONFIG_FILE_LOCATION = "com/javawebside/one2one/p1/hibernate.cfg.xml";
/** Holds a single instance of Session */
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
/** The single instance of hibernate configuration */
private static final Configuration cfg = new Configuration();
/** The single instance of hibernate SessionFactory */
private static org.hibernate.SessionFactory sessionFactory;
/**
* Returns the ThreadLocal Session instance. Lazy initialize
* the <code>SessionFactory</code> if needed.
*
* @return Session
* @throws HibernateException
*/
public static Session currentSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
try {
cfg.configure(CONFIG_FILE_LOCATION);
sessionFactory = cfg.buildSessionFactory();
} catch (Exception e) {
System.err
.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}
return session;
}
/**
* Close the single hibernate session instance.
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
}
}
/**
* Default constructor.
*/
private HibernateSessionFactory() {
}
}