第二次作业 单例模式的SessionFactory以及线程安全的session

单例模式的SessionFactory

在这个工具类Hibernate.java中写一个通过静态代码块生成唯一的SessionFactory，通过一个方法返回一个SessionFactory

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

public class HibernateUtil {
    private static Configuration cfg;
    private static SessionFactory sessionFactory;
    static {
        try {
            cfg = new Configuration().configure();
            sessionFactory = cfg.buildSessionFactory();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

线程安全的session

一、获取session

在学习中已经知道有两种方法可以获取session

1.openSession()

2.getCurrentSession()

在这里，这两种方法的区别：

采用getCurrentSession()创建的Session会绑定到当前的线程中去、而采用OpenSession()则不会。

采用getCurrentSession()创建的Session在commit或rollback后会自动关闭，采用OpenSession()必须手动关闭。

二、这里使用线程安全的Session

Configuration configuration = new Configuration.configure();
SessionFactory sessionFactory = configuration.buildSessionFactory();
Session session = sessionFactory.getCurrentSession()

三、演示实例

1.User类及配置

package com.domain;

public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    public Integer getId() {
        return id;
    }
    public void setId(Integer 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 Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", age=" + age + "]";
    }

}

<?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>
    <!-- name: 完整类名    table:数据库表名 -->
    <class name="com.domain.User" table="user">
        <!-- id配置表的主键  name代表表中属性 -->
        <id name="id" column="id">
            <!-- 主键生成策略 -->
            <generator class="native"></generator>
        </id>
        <property name="username" column="username" type="string"></property>
        <property name="password" column="password" type="string"></property>
        <property name="age" column="age" type="integer"></property>
    </class>
</hibernate-mapping>

2.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>
            <!-- 指定方言 -->
            <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
             <!-- 数据库驱动 -->
            <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
             <!-- 数据库url -->
            <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate02_1514010311</property>
             <!-- 数据库连接用户名 -->
            <property name="hibernate.connection.username">root</property>
             <!-- 数据库连接密码 -->
            <property name="hibernate.connection.password">0x3137</property>
            <!-- 将hibernate生成的sql语句打印到控制台 -->
            <property name="hibernate.show_sql">true</property>
            <!-- 将hibernate生成的sql语句格式化(语法缩进) -->
            <property name="hibernate.format_sql">true</property>
            <!-- 配置getCurrentSession -->
            <property name="hibernate.current_session_context_class">thread</property>
            <mapping resource="com/domain/User.hbm.xml" />
        </session-factory>

    </hibernate-configuration>

3.HibernateUtil.java

package com.util;

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

public class HibernateUtil {
    private static Configuration cfg;
    private static SessionFactory sessionFactory;
    static {
        try {
            cfg = new Configuration().configure();
            sessionFactory = cfg.buildSessionFactory();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

4.测试

package com.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.junit.Test;

import com.domain.User;
import com.util.HibernateUtil;

public class TestUser {
    @Test
    public void saveUser() {
        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction transaction = null;
        User user = new User();
        user.setUsername("三哥无邪");
        user.setPassword("1514010311");
        user.setAge(21);
        try {
            sessionFactory = HibernateUtil.getSessionFactory();
            session = sessionFactory.getCurrentSession();
            transaction = session.beginTransaction();
            session.save(user);
            transaction.commit();
        } catch (Exception e) {
            if (transaction!=null) {
                transaction.rollback();
            }
            e.printStackTrace();
        }
    }

    @Test
    public void updateUser() {

        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction transaction = null;
        try {
            sessionFactory = HibernateUtil.getSessionFactory();
            session = sessionFactory.getCurrentSession();
            transaction = session.beginTransaction();
            User user = session.get(User.class, 1);
            user.setUsername("三哥无邪啊");
            user.setPassword("1514010311");
            user.setAge(21);
            session.update(user);
            transaction.commit();
        } catch (Exception e) {
            if (transaction!=null) {
                transaction.rollback();
            }
            e.printStackTrace();
        }
    }

    @Test
    public void queryUser() {

        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction transaction = null;
        try {
            sessionFactory = HibernateUtil.getSessionFactory();
            session = sessionFactory.getCurrentSession();
            transaction = session.beginTransaction();
            User user = session.get(User.class, 2);
            System.out.println("ID:"+user.getId()+" 用户名："+user.getUsername()+" 密码："+user.getPassword());
            transaction.commit();
        } catch (Exception e) {
            if (transaction!=null) {
                transaction.rollback();
            }
            e.printStackTrace();
        }
    }
    @Test
    public void deleteUser() {

        SessionFactory sessionFactory = null;
        Session session = null;
        Transaction transaction = null;
        try {
            sessionFactory = HibernateUtil.getSessionFactory();
            session = sessionFactory.getCurrentSession();
            transaction = session.beginTransaction();
            User user = session.get(User.class, 1);
            session.delete(user);
            transaction.commit();
        } catch (Exception e) {
            if (transaction!=null) {
                transaction.rollback();
            }
            e.printStackTrace();
        }
    }
}

测试saveUser方法