6、hibernate映射数据类型

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。