简单的Hibernate访问数据库Demo

package com.jobhelp.domain;

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		//@Entity表示该类能被hibernate持久化
@Table(name="user")		//指定Entity对应的数据表名
public class Account {
	
	@Id		//指定该列为主键
	@GeneratedValue(strategy=GenerationType.AUTO)	//auto为自增长
	private Integer id;
	
	@Column(name="name")
	private String username;
	
	@Column(name="password")
	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;
	}

}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<!--表明以下的配置是针对session-factory配置的，SessionFactory是Hibernate中的一个类，这个类主要负责保存HIbernate的配置信息，以及对Session的操作 -->
	<session-factory>
		<!--配置数据库的驱动程序，Hibernate在连接数据库时，需要用到数据库的驱动程序 -->
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver </property>
		<!--设置数据库的连接url:jdbc:mysql://localhost/hibernate,其中localhost表示mysql服务器名称，此处为本机， 
			hibernate是数据库名 -->
		<property name="hibernate.connection.url">
			jdbc:mysql://localhost/User
		</property>
		<!--连接数据库是用户名 -->
		<property name="hibernate.connection.username">root </property>
		<!--连接数据库是密码 -->
		<property name="hibernate.connection.password">123456 </property>
		<!--数据库连接池的大小 -->
		<property name="hibernate.connection.pool.size">20 </property>
		<!--是否在后台显示Hibernate用到的SQL语句，开发时设置为true，便于差错，程序运行时可以在Eclipse的控制台显示Hibernate的执行Sql语句。项目部署后可以设置为false，提高运行效率 -->
		<property name="hibernate.show_sql">true </property>
		<!--jdbc.fetch_size是指Hibernate每次从数据库中取出并放到JDBC的Statement中的记录条数。Fetch Size设的越大，读数据库的次数越少，速度越快，Fetch 
			Size越小，读数据库的次数越多，速度越慢 -->
		<property name="jdbc.fetch_size">50 </property>
		<!--jdbc.batch_size是指Hibernate批量插入,删除和更新时每次操作的记录数。Batch Size越大，批量操作的向数据库发送Sql的次数越少，速度就越快，同样耗用内存就越大 -->
		<property name="jdbc.batch_size">23 </property>
		<!--jdbc.use_scrollable_resultset是否允许Hibernate用JDBC的可滚动的结果集。对分页的结果集。对分页时的设置非常有帮助 -->
		<property name="jdbc.use_scrollable_resultset">false </property>
		<!--connection.useUnicode连接数据库时是否使用Unicode编码 -->
		<property name="Connection.useUnicode">true </property>
		<!--connection.characterEncoding连接数据库时数据的传输字符集编码方式，最好设置为gbk，用gb2312有的字符不全 -->
		<!--  <property name="connection.characterEncoding">gbk </property>-->

		<!--hibernate.dialect 只是Hibernate使用的数据库方言,就是要用Hibernate连接那种类型的数据库服务器。 -->
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect </property>
		<!--指定映射文件为&ldquo;hibernate/ch1/UserInfo.hbm.xml&rdquo; -->
		<!-- <mapping resource="org/mxg/UserInfo.hbm.xml"> -->
		<mapping class="com.jobhelp.domain.Account"></mapping>
	</session-factory>
</hibernate-configuration>

package com.jobhelp.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

public class HibernateUtil {

	private static final SessionFactory sessionFactory;//单例模式的SessionFactory
	
	//static代码块，类加载时初始化hibernate，单例只初始化一次
	static{
		try{
			//从hibernate.cfg.xml中加载配置
			//加载@注解配置的实体类用AnnotationConfiguration()
			//加载xml配置的实体类使用Configuration()
			sessionFactory = new AnnotationConfiguration()
						.configure("hibernate.cfg.xml").buildSessionFactory();
		} catch (Throwable ex){
			System.err.println("Initial SessionFactory Error");
			throw new ExceptionInInitializerError(ex);
		}
	}
	
	public static SessionFactory getSessionFactory(){
		return sessionFactory;
	}
}

mysql> select * from user;
+----+-------+----------+
| id | name  | password |
+----+-------+----------+
|  1 | admin | 123456   |
|  2 | bowen | 123456   |
|  3 | tom   | 123456   |
|  4 | jack  | 123456   |
+----+-------+----------+

package com.jobhelp.util;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.jobhelp.domain.Account;

public class Test {
	
	public static void main(String[] agrs){
		/*Account account =new Account();
		account.setUsername("jack");
		account.setPassword("123456");*/
		
		//start a hibernate session
		Session session = HibernateUtil.getSessionFactory().openSession();
		//start a transaction
		Transaction transaction = session.beginTransaction();
		
		//insert into database
		//session.persist(account);
		
		@SuppressWarnings("all")
		//hql query
		List<Account> list =session.createQuery("from Account").list();
		
		//print query result
		for(Account account2: list){
			System.out.println(account2.getId()+" : "+account2.getUsername());
		}
		
		transaction.commit();
		session.close();
	}

}

[2014-11-24 21:26:19,083][DEBUG][org.hibernate.jdbc.AbstractBatcher:366] - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
[2014-11-24 21:26:19,083][DEBUG][org.hibernate.SQL:401] - select account0_.id as id0_, account0_.password as password0_, account0_.name as name0_ from user account0_
Hibernate: select account0_.id as id0_, account0_.password as password0_, account0_.name as name0_ from user account0_
......
[2014-11-24 21:26:19,108][DEBUG][org.hibernate.engine.StatefulPersistenceContext:787] - initializing non-lazy collections
1 : admin
2 : bowen
3 : tom
4 : jack
[2014-11-24 21:26:19,109][DEBUG][org.hibernate.transaction.JDBCTransaction:103] - commit
......