本节简介：

1　　　　单一主键的两种赋值方式：手动赋值（assigned）和自动赋值（native）

2　　　　mysql和oracle赋值的不同形式

3　　　　demo

2　　　　native由底层数据库生成标识符，如果是MySQL，就是increment,如果是oracle就是sequence.

注意：mysql的increment生成主键的形式不能用于集群。

3　　　　demo:

hibernate.cft.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
  "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
     <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
     <property name="connection.url">jdbc:mysql://localhost:3306/bendi</property>
     <property name="connection.username">root</property>
     <property name="connection.password">weidoudou</property>
     <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
     
     <property name="show_sql">true</property>
     <property name="format_sql">true</property>
     <property name="hbm2ddl.auto">update</property>
  
  <mapping resource = "Student.hbm.xml"/>     
    </session-factory>
</hibernate-configuration>

Student.hbm.xml

<?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 2017-12-20 0:42:12 by Hibernate Tools 3.4.0.CR1 --> <hibernate-mapping>     <class name="com.ddwei.student.Student" table="STUDENT">         <id name="pid" type="int">             <column name="PID" />             <generator class="native" />         </id>         <property name="name" type="java.lang.String">             <column name="NAME" />         </property>         <property name="sex" type="java.lang.String">             <column name="SEX" />         </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>

StudentTest.java

package hibernate_001;

import java.util.Date;

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

import com.ddwei.student.Student;

public class StudentTest {    private SessionFactory sessionFactory;  private Session session;  private Transaction trasaction;    @Test  public void testSaveStudent(){ //  Student student =new Student(1,"*","男",new Date(),"绍兴");//创建学生对象   Student student = new Student();   student.setName("秦始皇");   student.setSex("男");   student.setBirthday(new Date());   student.setAddress("阿房宫");   session.save(student);//会话保存学生对象进入数据库  }    @Before  public void init(){   //1  创建配置对象   Configuration config = new Configuration().configure();   //2  创建服务对象   ServiceRegistry serviceRe = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();      //3  创建会话工厂   sessionFactory = config.buildSessionFactory(serviceRe);      //4  打开会话   session = sessionFactory.openSession();   //5  创建事务   trasaction = session.beginTransaction();  }      @After  public void destroy(){   trasaction.commit();   session.close();   sessionFactory.close();  }

}