新建我們的Dynamic Web Project,取名爲"ssh_annotation”,配置Tomcat6.0的支持,打開MySQL,建立一個空數據庫,取名爲"ssh_annotation"。記得,要引進MySQL的JDBC驅動包mysql-connector-java-5.0.8-bin.jar。
在解壓縮的hibernate-distribution-3.3.1.GA目錄中,把hibernate.jar,和\lib\required\下的所用jar包引進到我們項目的lib目錄下。
不知道用過Hibernate3.3開發的朋友會不會遇到過這樣的問題:把上面的包都準備好的,開發Hibernate測試類時,會報Caused by: java.lang.NoClassDefFoundError: org/slf4j/impl/StaticLoggerBinder 或者Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/LogManager的錯誤。這是因爲Hibernate3.3提供的jar包,缺少了slf4j-log4j12.jar這個包。解決辦法是:在Hibernate的官方網站上下載hibernate-annotations-3.4.0.GA.zip,解壓縮,把其\lib\下的slf4j-log4j12.jar引進我們項目的lib目錄下。而我們引進這個jar包後,若我們沒有引進log4j.jar的話,就會報java.lang.NoClassDefFoundError: org/apache/log4j/LogManager的錯誤,可能是slf4j-log4j12.jar要用調用log4j的類吧。我們也引進log4j.jar即行。 當然,hibernate-annotations-3.4.0.GA.zip 是我們開發Hibernate Annotation所要用到的,除以上面那些jar包外,我們還要引進其hibernate-annotations.jar,及其\lib\下的hibernate-commons-annotations.jar,ejb3-persistence.jar。好,暫時就這些,我們接下來需要用到哪些jar包時再引進。
好,第一步,來開發我們的實體類User。代碼如下:
package com.rong.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="tb_user")
public class User {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
@Column(name="username", length=15)
private String username;
@Column(name="password", length=15)
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
簡單解釋一下吧:
@Entity定義User類爲實體類,@Id定義該屬性對應的列爲主鍵,@GeneratedValue(strategy=GenerationType.IDENTITY)定義主鍵生成策略爲Indentity,適用於MySQL和MS SQL等數據庫。@Column(name="username", length=15)定義列名和取值長度。
當然,必要的XML配置文件還是要有的:
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/ssh_annotation</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<!-- 數據庫言 -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- 將Session扔到線程裏去處理 -->
<property name="current_session_context_class">thread</property>
<!-- 在控制檯打印SQL語句 -->
<property name="show_sql">true</property>
<!-- 自動把實體類與屬性映射成數據庫中的表與列 -->
<property name="hbm2ddl.auto">update</property>
<!--
<mapping resource="com/rong/entity/User.hbm.xml"/>
-->
<!-- 在Hibernate中註冊User實體類,區別於上面註釋掉的resource寫法 -->
<mapping class="com.rong.entity.User"/>
</session-factory>
</hibernate-configuration>
接下來,我們來開發一個包裝器類,取名HibernateUtil,代碼如下:
package test.rong.hibernate;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
public class HibernateUtil {
private static final String CONFIG_FILE = "conf/hibernate.cfg.xml";
private static final SessionFactory sessionFactory;
static {
try {
//用xxx.hbm.xml形式配置實體映射
//sessionFactory = new Configuration().configure().buildSessionFactory();
//用Annotation形式配置實體映射
//默認的hibernate.cfg.xml必須在項目的classes目錄下 不然的話需要指定路徑
//我在這裏默認是我指定的路徑優先 如果沒有就在classes目錄下尋找
String filePath = HibernateUtil.class.getResource("/") + CONFIG_FILE;
File file = new File(filePath.replace("file:/", ""));
if(file.exists()){
sessionFactory = new AnnotationConfiguration().configure(file).buildSessionFactory();
}else{
sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
}
} catch (Throwable ex) {
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
接下來,我們還要實現一個ServletContextListener,以便在web.xml初始化的時候調用hibernate配置文件
package test.rong.hibernate;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class HibernateListener implements ServletContextListener {
public void contextInitialized(ServletContextEvent event) {
HibernateUtil.getSessionFactory(); // Just call the static initializer of that class
}
public void contextDestroyed(ServletContextEvent event) {
HibernateUtil.getSessionFactory().close(); // Free all resources
}
}
最後在web.xml裏面加上
<listener>
<listener-class>org.mypackage.HibernateListener</listener-class>
</listener>
到這裏,我們可以運行Tomcat,Hibernate會根據hbm2ddl.auto自動地把實體類與屬性轉變成數據庫中的表與列。但這一步,要事先在數據庫中建立一個名爲"ssh_annotation"的空數據庫。好了,看一下,你的數據庫中是否有"tb_user"的表生成了?!
下面,我們來進行測試,下載最新版本的Junit4.0.jar,試一下感覺如何。當然,舊版本的應該也沒問題的啦!寫測試代碼如下:
package test.rong.hibernate;
import java.util.Iterator;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.junit.Before;
import org.junit.Test;
import com.rong.entity.User;
public class EntityTest {
private Session session;
@Before
public void initSession(){
this.session = HibernateUtil.getSessionFactory().openSession();
}
@Test //測試添加用戶
public void testSave(){
session.beginTransaction();
User user = new User();
user.setUsername("rongxh7");
user.setPassword("blogjava");
session.save(user);
session.getTransaction().commit();
}
@Test //測試查詢用戶列表
@SuppressWarnings("unchecked")
public void testQuery(){
session.beginTransaction();
Query query = session.createQuery("from User u");
List<User> users = query.list();
for(Iterator<User> it = users.iterator() ; it.hasNext() ; ){
User user = it.next();
System.out.println("username = " + user.getUsername());
}
session.beginTransaction().commit();
}
@Test //測試查詢單個用戶
public void testGet(){
session.beginTransaction();
User user = (User)session.get(User.class, 1);
System.out.println("username = " + user.getUsername());
session.getTransaction().commit();
}
@Test //測試查詢修改用戶
public void testUpdate(){
session.beginTransaction();
User user = (User)session.load(User.class, 1);
user.setPassword("hello blogjava");
session.update(user);
session.getTransaction().commit();
}
@Test //測試刪除用戶
public void testDelete(){
session.beginTransaction();
session.delete(session.load(User.class, 1));
session.getTransaction().commit();
}
}
到此,我們的Hibernate Annotation開發完成了。
本文山寨 和原文有出入 轉載自http://www.blogjava.net/rongxh7/archive/2009/03/23/261577.html