一口一口吃掉Hibernate（一）——使用SchemaExport生成数据表

      Hibernate是一个开放源代码的对象关系映射框架，它对JDBC进行了非常轻量级的对象封装，使得Java程序员可以随心所欲的使用对象编程思维来操纵数据库。

      今天就来演示一下Hibernate最初级的操作，使用SchemaExport创建数据表。

      1.首先建立POJO类

package com.bjpowernode.hibernate;

import java.util.Date;

/**
 * 用户
 * @author Longxuan
 *
 */
public class User {
	
	private String  id;
	
	private String name;
	
	private String password;
	
	private Date createTime;
	
	private Date expireTime;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public Date getCreateTime() {
		return createTime;
	}

	public void setCreateTime(Date createTime) {
		this.createTime = createTime;
	}

	public Date getExpireTime() {
		return expireTime;
	}

	public void setExpireTime(Date expireTime) {
		this.expireTime = expireTime;
	}
	
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.bjpowernode.hibernate.User" >
		<!--hibernate为我们生成主键id-->
		<id name="id">
			<generator class="uuid" />
		</id>
		
		<!--默认把类的变量映射为相同名字的表列，当然我们使用column属性修改表字段-->
		<property name="name" column="name"></property>
		<property name="password"></property>
		<property name="createTime"></property>
		<property name="expireTime"></property>
	</class>
</hibernate-mapping>

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory name="foo">
		<!-- 数据库的连接也可以直接使用hibernate.properties文件 -->
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_test</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">root</property>
		
		<property name="hibernate.dialect" >org.hibernate.dialect.MySQLDialect</property><!-- 指定sql方言 -->
		<property name="hibernate.show_sql">true</property><!-- 设置是否显示生成sql语句 -->
		<property name="hibernate.format_sql">true</property><!-- 设置是否格式化sql语句-->
		
		<mapping resource="com/bjpowernode/hibernate/User.hbm.xml"  />
	</session-factory>
</hibernate-configuration>

package com.bjpowernode.hibernate;

import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;



/**
 * 将hbm生成ddl
 * @author Longxuan
 *
 */
public class ExportDB {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		// 默认读取hibernate.cfg.xml文件
		Configuration cfg = new Configuration().configure();
		
		// 生成并输出sql到文件（当前目录）和数据库
		SchemaExport export = new SchemaExport(cfg);
		
		// true 在控制台打印sql语句，true 导入sql语句到数据库，即可执行
		export.create(true, true);
	}
}

### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.rootLogger=warn, stdout

      现在可以测试了。首先在mysql中创建hibernate_test数据库：

      运行ExportDB的main方法，结果如图：