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Hibernate入门教程 jsp Hibernate入门教程

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想了解jsp Hibernate入门教程的相关内容吗,在本文为您仔细讲解Hibernate入门教程的相关知识和一些Code实例,欢迎阅读和指正,我们先划重点:jsp,Hibernate,入门教程,下面大家一起来学习吧。
例如:
复制代码 代码如下:

HibernateTest.java
import onlyfun.caterpillar.*;
import net.sf.hibernate.*;
import net.sf.hibernate.cfg.*;
import java.util.*;
public class HibernateTest {
public static void main(String[] args) throws HibernateException {
SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.openSession();
List users = session.find("from User");
User updated = null;
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
if(updated == null)
updated = user;
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
updated.setName("justin");
session.flush();
users = session.find("from User");
session.close();
sessionFactory.close();
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
}
}

 这个程序会显示数据表中的所有数据,并将数据表中的第一笔数据更新,一个执行的结果如下:
log4j:WARN No appenders could be found for logger (net.sf.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
caterpillar
Age: 28
Sex: M
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F
Hibernate: update USER set name=?, sex=?, age=? where user_id=?
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
justin
Age: 28
Sex: M
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F

 如果您开启了一个Session,从数据表中取出数据显示到使用者接口上,之后关闭Session,当使用者在接口上操作完毕并按下储存时,这时您要重新开启一个Session,使用update()方法将对象中的数据更新至对应的数据表中,一个例子如下: 
复制代码 代码如下:

HibernateTest.java
import onlyfun.caterpillar.*;
import net.sf.hibernate.*;
import net.sf.hibernate.cfg.*;
import java.util.*;
public class HibernateTest {
public static void main(String[] args) throws HibernateException {
SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.openSession();
List users = session.find("from User");
// 关闭这个Session
session.close();
User updated = null;
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
if(updated == null)
updated = user;
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
// 使用者作一些操作,之后储存
updated.setName("caterpillar");
// 开启一个新的Session
session = sessionFactory.openSession();
// 更新数据
session.update(updated);
users = session.find("from User");
session.close();
sessionFactory.close();
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
}
}

 这个程序执行的结果范例如下,您可以看看实际上执行了哪些SQL:
log4j:WARN No appenders could be found for logger (net.sf.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
justin
Age: 28
Sex: M
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F
Hibernate: update USER set name=?, sex=?, age=? where user_id=?
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
caterpillar
Age: 28
Sex: M
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F

 Hibernate提供了一个saveOrUpdate()方法,为数据的储存或更新提供了一个统一的操作接口,藉由定义映像文件时,设定<id>标签的unsaved-value来决定什么是新的值必需,什么是已有的值必须更新:
User.hbm.xml
复制代码 代码如下:

<id name="id" type="string" unsaved-value="null">
<column name="user_id" sql-type="char(32)" />
<generator class="uuid.hex"/>
</id>

unsaved-value
可以设定的值包括:
any - 总是储存
none - 总是更新
null - id为null时储存(预设)
valid - id为null或是指定值时储存
 这样设定之后,您可以使用session.saveOrUpdate(updated);来取代上一个程序的session.update(updated);方法。
 如果要删除数据,只要使用delete()方法即可,直接看个例子。
复制代码 代码如下:

HibernateTest.java
import onlyfun.caterpillar.*;
import net.sf.hibernate.*;
import net.sf.hibernate.cfg.*;
import java.util.*;
public class HibernateTest {
public static void main(String[] args) throws HibernateException {
SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.openSession();
List users = session.find("from User");
User updated = null;
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
if(updated == null)
updated = user;
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
session.delete(updated);
users = session.find("from User");
session.close();
sessionFactory.close();
for (ListIterator iterator = users.listIterator(); iterator.hasNext(); ) {
User user = (User) iterator.next();
System.out.println(user.getName() +
"\n\tAge: " + user.getAge() +
"\n\tSex: " + user.getSex());
}
}
}

 一个执行的结果范例如下:
log4j:WARN No appenders could be found for logger (net.sf.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
justin
Age: 28
Sex: M
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F
Hibernate: delete from USER where user_id=?
Hibernate: select user0_.user_id as user_id, user0_.name as name, user0_.sex as sex, user0_.age as age from USER user0_
momor
Age: 25
Sex: F
Bush
Age: 25
Sex: M
Becky
Age: 35
Sex: F
 Hibernate对于数据的更新、删除等动作,是依懒id值来判定,如果您已知id值,则可以使用load()方法来加载资料,例如:
User user = (User) session.load(User.class, id);
 更多有关于Hibernate资料更新操作的说明,您可以看看参考手册的第九章内容。

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