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。