hibernate_02_session介绍

什么是session？

hibernate的session对象就相当于jdbc的connection。我们对数据库的操作（增删改等）都是使用的session方法。

写一个java类

package com.imooc.hibernate;

import java.util.Date;

public class Students {

    private int sid;
    private String sname;
    private String gender;
    private Date birthday;
    private String address;

    public Students(int sid, String sname, String gender, Date birthday, String address) {
        super();
        this.sid = sid;
        this.sname = sname;
        this.gender = gender;
        this.birthday = birthday;
        this.address = address;
    }

    @Override
    public String toString() {
        return "Students [sid=" + sid + ", sname=" + sname + ", gender=" + gender + ", birthday=" + birthday
                + ", address=" + address + "]";
    }

    public int getSid() {
        return sid;
    }

    public void setSid(int sid) {
        this.sid = sid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public String getGender() {
        return gender;
    }

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

    public Date getBirthday() {
        return birthday;
    }

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

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

生成类的配置文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-5-23 0:24:09 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="com.imooc.hibernate.Students" table="STUDENTS">
        <id name="sid" type="int">
            <column name="SID" />
            <generator class="assigned" />
        </id>
        <property name="sname" type="java.lang.String">
            <column name="SNAME" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="GENDER" />
        </property>
        <property name="birthday" type="java.util.Date">
            <column name="BIRTHDAY" />
        </property>
        <property name="address" type="java.lang.String">
            <column name="ADDRESS" />
        </property>
    </class>
</hibernate-mapping>

配置hibernate.cfg.xml文件

<?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>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate?useUnicode=true&amp;characterEncoding=UTF-8</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <!-- 是否将sql语句打印到控制台，编码阶段便于测试，建议设为true -->
        <property name="show_sql">true</property>
        <!-- 是否将sql语句进行排版，建议设为true -->
        <property name="format_sql">true</property>
        <!-- 生成表结构的策略。create是如果之前有表结构，先删除表结构再重建；
            update：原有的基础上更新；
            create-drop：先删除表结构再重建
            validate：与原表进行验证，如果和原表表结构不同，则不进行创建。
            一般使用create和update
         -->
        <property name="hbm2ddl.auto">create</property>
        
        <mapping resource="com/imooc/hibernate/Students.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

如果不使用事务，hibernate不会在数据库生成相应的数据。当然，即使不使用事务，也不是没办法写入数据库。方法如下：

package com.icoom.test;
import static org.junit.Assert.fail;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.jdbc.Work;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.imooc.hibernate.Students;

public class StudentsTest {
    
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction transaction;

    @Before
    public void init() {
        // 1.创建配置对象
        Configuration config = new Configuration().configure();
        // 2.创建服务注册对象
        ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
        // 3.创建会话工厂对象
        sessionFactory = config.buildSessionFactory(serviceRegistry);
        // 会话对象
        session = sessionFactory.openSession();
        // 开启事务(注意：不开启事物就不能将对象保存在数据库中)
//        transaction = session.beginTransaction();
    }
    @After
    public void destory() {
//        transaction.commit();
        session.close();
        sessionFactory.close();
    }
    @Test
    public void testSaveStudents() {
        // 生成学生对象
        Students s = new Students(1, "老张", "男", new Date(), "山东");
        //如果不使用事务，又想将数据像jdbc一样自动提交到数据库中，可以使用session.doWork方法
        session.doWork(new Work(){

            @Override
            public void execute(Connection connection) throws SQLException {
                connection.setAutoCommit(true);
            }
            
        });
        session.save(s);//保存对象进入数据库
        session.flush();
    }

}

但是不推荐使用这种办法。