Hibernate 简单使用（二） JDBC封装

上一篇介绍了Hibernate框架的搭建与简单使用~

这一次就介绍一下Session的封装~

因为Session是线程不安全的，为了保证当前线程只有一个session对象，并且当前线程中的Session不能让其他线程来访问，需要将获取Session的方法进行封装，为了保证Session的线程安全性，需要将Session放到ThreadLocal中。

ThreadLocal为线程本地变量

上一篇Test类中，我贴下代码：

public class Test {public static void main(String[] args) {// TODO Auto-generated method stub//1.创建配置对象Configuration configuration=new Configuration();//2.读取配置对象configuration.configure();//3.根据配置文件信息创建一级缓存，SessionFactory/* * Connection * 映射文件，映射对象 * HttpSession 用户与服务器之间的会话 * Session  代码与数据库之间的会话 */SessionFactory ss=configuration.buildSessionFactory();//4.创建Session，打开会话Session session=ss.openSession();//5.开启事务Transaction tran=session.beginTransaction();session.save(new User(null, "张二", 100.0, new Date()));//6.事务的提交tran.commit();//7.session关闭session.close();System.out.println("1111111111111111111");}}

有些代码是可以封装起来的~这样就可以使Session线程安全~

如图：

每次session都要开启一个事务，前面的代码就可以封装起来，这样就会减少代码的编写量~

步骤：

1.新建一个类：HibernateSessioFactory

<span style="font-size:14px;">public class HibernateSessioFactory {private static SessionFactory sessionFactory;//用于存放Session，该对象是线程安全的，只有当前线程才能访问private static ThreadLocal<Session>threadLocal;static{Configuration config=new Configuration();config.configure();sessionFactory=config.buildSessionFactory();threadLocal=new ThreadLocal<Session>();}public static Session getSession(){Session session=threadLocal.get();if(session==null||!session.isOpen()){session=sessionFactory.openSession();threadLocal.set(session);}return session;}}</span>

在这个类中通过getSession可以获得session~

这样就封装成功了~注释已经说得很清楚，我就不说了，不懂的话去看我上一篇~

2.写一个简单的例子，来简单使用HibernateSessioFactory，也简单学习一下封装代码的好处。

User类：

public class User implements Serializable{private static final long serialVersionUID = 1L;Long id;String name;Double account;Date birthday;public User() {super();// TODO Auto-generated constructor stub}public User(Long id, String name, Double account, Date birthday) {super();this.id = id;this.name = name;this.account = account;this.birthday = birthday;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Double getAccount() {return account;}public void setAccount(Double account) {this.account = account;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}@Overridepublic String toString() {return "User [id=" + id + ", name=" + name + ", account=" + account + ", birthday=" + birthday + "]";}}

UserDao类：

public class UserDao {private Session getSession(){return HibernateSessioFactory.getSession();}public void save(User user){Session session=getSession();System.out.println("dao:"+session.hashCode());session.save(user);}public void deleteByID(long id){Session session=getSession();User user=(User) session.load(User.class, id);session.delete(user);}}

UserService类：

在这个类中写了个register方法~调用了UserDao类中的save方法~

public class UserService {private UserDao userDao=new UserDao();public void register(User user){Session session=HibernateSessioFactory.getSession();System.out.println("service:"+session.hashCode());Transaction transaction=session.beginTransaction();//开启事务userDao.save(user);//增删改查transaction.commit();//事务的提交session.close();}}

MainTest类-程序的入口：

public class MainTest {public static void main(String[] args) {UserService userService=new UserService();System.out.println(1111111111);userService.register(new User(null, "新添加的", 891.1,new Date()));}}

这里给大家解释一下，如图：

在这里代码已经基本完成了，但是不要忘记配置文件和映射文件啊~

配置文件hibernate.cfg.xml：

<?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><session-factory><!-- Database connection settings --><property name="connection.driver_class">com.mysql.jdbc.Driver</property><property name="connection.url">jdbc:mysql://127.0.0.1:3306/ssh</property><property name="connection.username">root</property><property name="connection.password">root</property><!-- SQL dialect --><property name="dialect">org.hibernate.dialect.MySQLDialect</property><!-- Echo all executed SQL to stdout --><property name="show_sql">true</property><property name="format_sql">true</property><!-- Drop and re-create the database schema on startup --><property name="hbm2ddl.auto">update</property>     <mapping resource="com/xu/day5/cms/dao/use.hbm.xml" /></session-factory></hibernate-configuration>

映射文件use.hbm.xml：

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.xu.day5.cms.dao"><class name="User" table="tb_user"><id name="id" column="id"><generator class="increment" /></id><property name="name" /><property name="account" /><property name="birthday" /></class></hibernate-mapping>

效果图我就不贴了~

有问题的可以和我一起交流~