学步园

hibernate数据类型与java和sql的对应关系，参见4中的图：

创建一个含有多种数据类型的JavaBean：

import java.sql.Date;
import java.sql.Timestamp;

public class People
{
	private Long id;
	
	private String username;
	
	private String password;
	
	private int telphone;
	
	private char gender; //'M','F'
	
	private boolean graduation;
	
	private Date birthday;
	
	private Timestamp marrrTime;
	
	private byte[] file;

	public Long getId()
	{
		return id;
	}

	public void setId(Long 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 int getTelphone()
	{
		return telphone;
	}

	public void setTelphone(int telphone)
	{
		this.telphone = telphone;
	}

	public char getGender()
	{
		return gender;
	}

	public void setGender(char gender)
	{
		this.gender = gender;
	}

	public boolean isGraduation()
	{
		return graduation;
	}

	public void setGraduation(boolean graduation)
	{
		this.graduation = graduation;
	}

	public Date getBirthday()
	{
		return birthday;
	}

	public void setBirthday(Date birthday)
	{
		this.birthday = birthday;
	}

	public Timestamp getMarrrTime()
	{
		return marrrTime;
	}

	public void setMarrrTime(Timestamp marrrTime)
	{
		this.marrrTime = marrrTime;
	}

	public byte[] getFile()
	{
		return file;
	}

	public void setFile(byte[] file)
	{
		this.file = file;
	}
	
	
}

编写相应的hbm.xml文件：

<?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>
	
	<class name="com.cdtax.model.People" table="people">
	
		<id name="id" column="id" type="long">
			<generator class="increment"></generator>
		</id>
		
		<property name="username" column="username" type="string"></property>
		<property name="password" column="password" type="string"></property>
		<property name="telphone" column="telphone" type="int"></property>
		<property name="gender" column="gender" type="character"></property>
		<property name="graduation" column="graduation" type="boolean"></property>
		<property name="birthday" column="birthday" type="date"></property>
		<property name="marryTime" column="marryTime" type="timestamp"></property>
		<property name="file" column="file" type="binary"></property>
				
	</class>
</hibernate-mapping>

这个文件中的type属性值表示数据类型，这里写的是hibernate的数据类型，也可以写java的数据类型

创建数据库表：

CREATE TABLE `people` (
  `id` bigint(20) NOT NULL default '0',
  `username` varchar(50) default NULL,
  `password` varchar(20) default NULL,
  `telphone` int(11) default NULL,
  `gender` char(1) default NULL,
  `graduation` bit(1) default NULL,
  `birthday` date default NULL,
  `marryTime` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
  `file` blob,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

注意表、JavaBean和People.hbm.xml中三者之间数据类型的对应关系。

有了hbm.xml文件，可以自动产生JavaBean，做法是：

右键单击People.hbm.xml文件，点击MyEclipse——>generate POJOs

在MyEclipse的数据库视图中连接数据库后，可以通过数据库表，直接生成hbm.xml文件，作法：

在相关表上右键单击：Hibernate Reverse Engineering，在此可以选择四种不同的生成类别，选在第一项：create POLO <>DB Table mappinginformation，生成的hbm.xml如下：

<?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">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.cdtax.People" table="people" catalog="hibernate">
        <id name="id" type="java.lang.Long">
            <column name="id" />
            <generator class="assigned" />
        </id>
        <property name="username" type="java.lang.String">
            <column name="username" length="50" />
        </property>
        <property name="password" type="java.lang.String">
            <column name="password" length="20" />
        </property>
        <property name="telphone" type="java.lang.Integer">
            <column name="telphone" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="gender" length="1" />
        </property>
        <property name="graduation" type="java.lang.Boolean">
            <column name="graduation" />
        </property>
        <property name="birthday" type="java.util.Date">
            <column name="birthday" length="0" />
        </property>
        <property name="marryTime" type="java.sql.Timestamp">
            <column name="marryTime" length="0" />
        </property>
        <property name="file" type="java.lang.String">
            <column name="file" />
        </property>
    </class>
</hibernate-mapping>

可以看出这里的type使用的是Java类型。

写一个测试类：

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.sql.Timestamp;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class HibernateTest
{
	private static SessionFactory sessionFactory;
	
	static
	{
		try
		{
			sessionFactory = new Configuration().configure().buildSessionFactory();
		}
		catch(Exception ex)
		{
			ex.printStackTrace();
		}
	}
	public static void main(String[] args) throws Exception
	{
		People people = new People();
		
		people.setUsername("zhangsan");
		people.setPassword("123456");
		people.setGender('F');
		people.setBirthday(new java.sql.Date(new java.util.Date().getTime()));
		people.setGraduation(true);
		people.setTelphone(1234);
		people.setMarryTime(new Timestamp(new java.util.Date().getTime()));
		
		InputStream is = new FileInputStream("c:/222.ppt");
		
		int length = is.available();
		
		byte[] buffer = new byte[length];
		
		is.read(buffer);
		
		people.setFile(buffer);
		
		Session session = sessionFactory.openSession();
		Transaction tx = null;
		
		try
		{
			tx = session.beginTransaction();
			
			session.save(people);
			
			tx.commit();
		}
		catch(Exception ex)
		{
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}
	}
}

对于mysql，有一个max_allowed_packet参数，如果设置过小，在插入blob数据数有可能异常。

查询数据库数据并显示结果将main方法修改如下：

Session session = sessionFactory.openSession();
		Transaction tx = null;
		try
		{
			tx = session.beginTransaction();
			
			Query query = session.createQuery("from People as p order by p.username");
			
			List<People> list = (List<People>)query.list();
			
			
			for(Iterator<People> iter = list.iterator();iter.hasNext();)
			{
				People people = iter.next();
				
				System.out.println(people.getUsername());
				System.out.println(people.getPassword());
				System.out.println(people.getTelphone());
				System.out.println(people.getBirthday());
				System.out.println(people.getId());
				System.out.println(people.getMarryTime());
				System.out.println(people.getGender());
				System.out.println(people.isGraduation());
				
				System.out.println("---------");
				byte[] buffer = people.getFile();
				
				OutputStream os = new FileOutputStream("c:/" + people.getId() + ".ppt");
				
				os.write(buffer);
				os.close();
			}
		}
		catch(Exception ex)
		{
			System.out.println("yichang");
			ex.printStackTrace();
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}
	}

对于分页操作来说，需要知道如下一些信息：当前正在操作的是第几页、每一页显示多少条记录数。

修改query为：

Query query = session.createQuery("from People as p order by p.id asc").setFirstResult(0).setMaxResults(20);

setFirstResult（）设置显示的第一条记录从结果集中开始的位置，setMaxResults(20)设置每页最多显示多少记录

更新操作：

修改main方法：

Session session = sessionFactory.openSession();
		
		Transaction tx = null;
		
		try
		{
			tx = session.beginTransaction();
			
			People people = (People)session.load(People.class, new Long(1));
			
			people.setUsername("xiugai111");
			people.setGender('M');
			
			people.setUsername("xiugai2222");
			people.setGender('F');
			
			people.setUsername("world");
			
			session.update(people);
			
			tx.commit();
		}
		catch(Exception ex)
		{
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}
		

更新操作涉及两个步骤，先是查询出要修改的记录，使用load方法，然后修改值，最后update方法更新。对于中间多次修改对象属性值，以最后一次为准。程序运行执行两条sql语句，一个是select，一个是update，如果将session.update(people);注释掉，结果一样，也是两条sql语句，更新也被执行了，如果将tx.commit()；也注释掉，则只会执行一条select语句，不会执行update语句，不能更新数据库记录。

删除操作：

Session session = sessionFactory.openSession();
		Transaction tx = null;
		
		try
		{
			tx = session.beginTransaction();
			Query query = session.createQuery("from People");
			
			Iterator<People> iter = (Iterator<People>)query.iterate();
			
			while(iter.hasNext())
			{
				session.delete(iter.next());
			}
			
			tx.commit();
		
		}
		catch(Exception ex)
		{
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}

执行的结果是：

Hibernate: select people0_.id as col_0_0_ from people people0_
Hibernate: select people0_.id as id0_0_, people0_.username as username0_0_, people0_.password as password0_0_, people0_.telphone as telphone0_0_, people0_.gender as gender0_0_, people0_.graduation as graduation0_0_, people0_.birthday as birthday0_0_, people0_.marryTime
as marryTime0_0_, people0_.file as file0_0_ from people people0_ where people0_.id=?
Hibernate: select people0_.id as id0_0_, people0_.username as username0_0_, people0_.password as password0_0_, people0_.telphone as telphone0_0_, people0_.gender as gender0_0_, people0_.graduation as graduation0_0_, people0_.birthday as birthday0_0_, people0_.marryTime
as marryTime0_0_, people0_.file as file0_0_ from people people0_ where people0_.id=?
Hibernate: select people0_.id as id0_0_, people0_.username as username0_0_, people0_.password as password0_0_, people0_.telphone as telphone0_0_, people0_.gender as gender0_0_, people0_.graduation as graduation0_0_, people0_.birthday as birthday0_0_, people0_.marryTime
as marryTime0_0_, people0_.file as file0_0_ from people people0_ where people0_.id=?
Hibernate: select people0_.id as id0_0_, people0_.username as username0_0_, people0_.password as password0_0_, people0_.telphone as telphone0_0_, people0_.gender as gender0_0_, people0_.graduation as graduation0_0_, people0_.birthday as birthday0_0_, people0_.marryTime
as marryTime0_0_, people0_.file as file0_0_ from people people0_ where people0_.id=?
Hibernate: select people0_.id as id0_0_, people0_.username as username0_0_, people0_.password as password0_0_, people0_.telphone as telphone0_0_, people0_.gender as gender0_0_, people0_.graduation as graduation0_0_, people0_.birthday as birthday0_0_, people0_.marryTime
as marryTime0_0_, people0_.file as file0_0_ from people people0_ where people0_.id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?

如果将程序修改一下：

Session session = sessionFactory.openSession();
		Transaction tx = null;
		
		try
		{
			tx = session.beginTransaction();
			Query query = session.createQuery("from People");
			/*
			Iterator<People> iter = (Iterator<People>)query.iterate();
			
			while(iter.hasNext())
			{
				session.delete(iter.next());
			}
			*/
			
			List<People> list = query.list();
			
			for(Iterator<People> iter = list.iterator();iter.hasNext();)
			{
				session.delete(iter.next());
			}
			tx.commit();
		
		}
		catch(Exception ex)
		{
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}

执行结果就是：

Hibernate: select people0_.id as id0_, people0_.username as username0_, people0_.password as password0_, people0_.telphone as telphone0_, people0_.gender as gender0_, people0_.graduation as graduation0_, people0_.birthday as birthday0_, people0_.marryTime
as marryTime0_, people0_.file as file0_ from people people0_
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?

差别：

对于Query接口的list()方法与iterator()方法来说，都可以实现获取查询的对象，但是list（）方法返回的每个对象都是完整的（对象中的每个属性都被表中的字段填充上了），而iterator（）方法所返回的对象中仅包含了主键值（标示符），只有当你对iterator（）中的对象进行操作时，hibernate才会向数据库再次发送SQL语句来获取该对象的属性值。

修改程序：

Session session = sessionFactory.openSession();
		Transaction tx = null;
		List<People> list = null;
		try
		{
			tx = session.beginTransaction();
			Query query = session.createQuery("from People");
			
//			Iterator<People> iter = (Iterator<People>)query.iterate();
//			
//			while(iter.hasNext())
//			{
//				session.delete(iter.next());
//			}
			
			
			list = query.list();
			
			for(Iterator<People> iter = list.iterator();iter.hasNext();)
			{
				session.delete(iter.next());
			}
			tx.commit();
		
		}
		catch(Exception ex)
		{
			if(null != tx)
			{
				tx.rollback();
			}
		}
		finally
		{
			session.close();
		}
		
		for(People people : list)
		{
			System.out.println(people.getUsername());
		}
	}

执行结果：

Hibernate: select people0_.id as id0_, people0_.username as username0_, people0_.password as password0_, people0_.telphone as telphone0_, people0_.gender as gender0_, people0_.graduation as graduation0_, people0_.birthday as birthday0_, people0_.marryTime
as marryTime0_, people0_.file as file0_ from people people0_
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
Hibernate: delete from people where id=?
zhang
zhang
zhan33

再次修改程序：

Session session = sessionFactory.openSession();
		Transaction tx = null;
//		List<People> list = null;
		
		Iterator<People> iter = null;
		try
		{
			tx = session.beginTransaction();
			Query query = session.createQuery("from People");
			
//			Iterator<People> iter = (Iterator<People>)query.iterate();
//			
//			while(iter.hasNext())
//			{
//				session.delete(iter.next());
//			}
			
			
//			list = query.list();
			
			iter = (Iterator<People>)query.iterate();
			
//			for(Iterator<People> iter = list.iterator();iter.hasNext();)
//			{
//				session.delete(iter.next());
//			}
			tx.commit();
		
		}
		catch(Exception ex)
		{
			ex.printStackTrace();
			if(null != tx)
			{
				tx.rollback();
			}
			
		}
		finally
		{
			session.close();
		}
		
//		for(People people : list)
//		{
//			System.out.println(people.getUsername());
//		}
		
		while(iter.hasNext())
		{
			System.out.println(iter.next().getId());
		}
	}
	

执行结果：

Hibernate: select people0_.id as col_0_0_ from people people0_
Exception in thread "main" org.hibernate.SessionException: Session is closed!
 at org.hibernate.impl.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:72)
 at org.hibernate.impl.SessionImpl.getPersistenceContext(SessionImpl.java:1835)
 at org.hibernate.type.ManyToOneType.scheduleBatchLoadIfNeeded(ManyToOneType.java:142)
 at org.hibernate.type.ManyToOneType.hydrate(ManyToOneType.java:128)
 at org.hibernate.type.EntityType.nullSafeGet(EntityType.java:227)
 at org.hibernate.impl.IteratorImpl.next(IteratorImpl.java:135)
 at com.cdtax.hibernate.HibernateTest.main(HibernateTest.java:257)
出现了异常

这就是iterator和list的差别，这是hibernate的延迟加载机制造成的，对于iterator，是延迟加载。只有在使用到时再加载对象。

对于MyEclipse的几个视图，可在hibernate视图下进行逆向工程。