MyEclipse环境下Hibernate入门实例
首先在MyEclipse下创建一个WebProject，项目命名为demo，然后【MyEclipse->project capablities->add hibernate capabilities】，跟着向导操作，最后会生成一个hibernate.cfg.xml和一个HibernateSessionFactory.java文件。在向导中要求填写一些数据库连接的配置信息以及HibernateSessionFactory存放的包，配置信息我们可以参考下面的hibernate.cfg.xml来填写，而HibernateSessionFactory我们放在com.demo.hibernate.util这个包里面。
1.HibernateSessionFactory.java
View Code
package com.demo.hibernate.util; 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. * Location should be on the classpath as Hibernate uses * #resourceAsStream style lookup for its configuration file. * The default classpath location of the hibernate config file is * in the default package. Use #setConfigFile() to update * the location of the configuration file for the current session. */ private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml"; private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static Configuration configuration = new Configuration(); private static org.hibernate.SessionFactory sessionFactory; private static String configFile = CONFIG_FILE_LOCATION; static { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) { System.err .println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } private HibernateSessionFactory() { } /** * Returns the ThreadLocal Session instance. Lazy initialize * the <code>SessionFactory</code> if needed. * * @return Session * @throws HibernateException */ public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory(); } session = (sessionFactory != null) ? sessionFactory.openSession() : null; threadLocal.set(session); } return session; } /** * Rebuild hibernate session factory * */ public static void rebuildSessionFactory() { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) { System.err .println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } /** * 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(); } } /** * return session factory * */ public static org.hibernate.SessionFactory getSessionFactory() { return sessionFactory; } /** * return session factory * * session factory will be rebuilded in the next call */ public static void setConfigFile(String configFile) { HibernateSessionFactory.configFile = configFile; sessionFactory = null; } /** * return hibernate configuration * */ public static Configuration getConfiguration() { return configuration; } }
2.hibernate.cfg.xml(在src目录下)
View Code
<?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"> <!-- Generated by MyEclipse Hibernate Tools. --> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- <property name="show_sql">true</property> --> <!-- 连接字符串 --> <property name="connection.url">jdbc:mysql://localhost:3306/demo</property> <property name="connection.username">root</property> <property name="connection.password">root</property> <!-- 数据库驱动 --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <!-- 映射文件，是后来添加的，不是想到自动生成的 --> <mapping resource="com/demo/hibernate/beans/User.hbm.xml"/> </session-factory> </hibernate-configuration>
3.创建数据库
在MySql中创建一个名为demo的数据库，然后将下面的代码另存为“*.sql”文件，再将该文件导入数据库。当然也可直接通过类似navicat的数据库UI来创建数据库。
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(50) DEFAULT NULL,
`password` varchar(50) DEFAULT NULL,
`email` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
4. *.hbm.xml映射文件
我们知道Hibernate是用户将对象与数据库表进行映射，那么下面编写映射文件：User.hbm.xml（在com.demo.hibernate.beans包中），从代码中我们可以看到name与column属性，name表示User类中的属性，column表示数据库表user中的字段名称。类中的属性和表中的字段可以不相同，如果相同的话column可以省略。比如下面的column="username" 和column="password" 可以省略不写。像<property name="email" /> 一样。
View Code
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- <hibernate-mapping package="com.demo.hibernate.beans"> --> <hibernate-mapping> <class name="com.demo.hibernate.beans.User" table="user"> <id name="id" column="ID" > <generator class="native" /> </id> <property name="username" column="username" /> <property name="password" column="password" /> <property name="email"/> </class> </hibernate-mapping>
5.编写持久化类User.java，
这里我们不一定要求User类中的属性与表user的字段相同，不过如果相同则可以省去一些步骤，就是前面提到的*.hbm.xml文件中的一些字段可以省略。
View Code
package com.demo.hibernate.beans; public class User { private int id; private String username; private String password; private String email; 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; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } }
6.编写DAO类UserDAO.java
DAO就是Database Access Objects，数据访问对象的英文缩写。顾名思义对数据库操作的方法都写在这个类中，就比如代码中getUser()方法就是需要读取数据库信息。不过hibernate因为通过映射的方法不直接使用SQL语句操纵数据库，而是引入了HQL语言。最明显的一点是：
Query query=session.createQuery("from User where username=?");
这里from User中的User是指User类而不是user表，HQL直接对对象操作。
View Code
package com.demo.hibernate.dao; import org.hibernate.HibernateException; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.Transaction; import com.demo.hibernate.beans.User; import com.demo.hibernate.util.HibernateSessionFactory; public class UserDAO { public User getUser(String username) throws HibernateException{ Session session=null; Transaction tx=null; User user=null; try { session=HibernateSessionFactory.getSession(); tx=session.beginTransaction(); Query query=session.createQuery("from User where username=?"); query.setString(0, username.trim()); user=(User)query.uniqueResult(); query=null; //session.save(user); tx.commit(); //session.close(); } // catch(HibernateException e) // { // throw e; // } // finally // { // if(tx!=null) // { // tx.rollback(); // } // HibernateSessionFactory.closeSession(); // } catch(HibernateException e) { System.out.println(e.getMessage()); e.printStackTrace(); } return user; } }
7.编写Service类并运行（含有主函数的类）
View Code
package com.demo.hibernate.service; import com.demo.hibernate.beans.User; import com.demo.hibernate.dao.UserDAO; public class UserService { public boolean valid(String username,String password) { UserDAO test=new UserDAO(); User user=test.getUser("admin"); if(user.getPassword().equals(password)) { return true; } else { return false; } } public static void main(String args[]) { UserService service=new UserService(); boolean login=service.valid("admin", "admin"); System.out.println("验证结果"+login); } }
8.显示结果：
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly.
验证结果：true