hibernate课程 初探单表映射2-6 session详解（下）

本节主要内容：

1　　　　介绍了getCurrentSession和opensession的区别

2　　　　demo:通过打印比较两个session是否相同，验证两个session是否是同一session

3　　　　demo:通过打印hashcode验证不关闭session,容易连接池溢出。

1　　　　getCurrentSession和opensession的区别

a　　getCurrentSession每次获取的都是同一连接，opensession每次获取的是不同的连接。

b　　getCurrentSession不需要手动关闭，在提交事务之后自动关闭。opensession需要手动关闭，如果不关闭的话，连接数枯竭，容易连接池溢出.

c　　getCurrentSession 必须开启事务transaction，opensession不是必须（自我总结的）

2　　　demo1

package hibernate_001;

import java.sql.Array; import java.sql.Blob; import java.sql.CallableStatement; import java.sql.Clob; import java.sql.DatabaseMetaData; import java.sql.NClob; import java.sql.PreparedStatement; import java.sql.SQLClientInfoException; import java.sql.SQLException; import java.sql.SQLWarning; import java.sql.SQLXML; import java.sql.Savepoint; import java.sql.Statement; import java.sql.Struct; import java.util.Date; import java.util.Map; import java.util.Properties; import java.util.TimeZone; import java.util.concurrent.Executor;

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.ddwei.student.Student; import com.mysql.jdbc.Connection; import com.mysql.jdbc.ExceptionInterceptor; import com.mysql.jdbc.Extension; import com.mysql.jdbc.MySQLConnection; import com.mysql.jdbc.log.Log;

public class StudentTest {    private SessionFactory sessionFactory;  private Session session;  private Transaction trasaction;    @Test  public void testSaveStudent(){   //获取配置对象，得到hibernate.cfg.xml配置的内容   Configuration config = new Configuration().configure();   //获取服务注册对象，获取hibernate.hbm.xml配置的内容   ServiceRegistry sry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();      SessionFactory sfy = config.buildSessionFactory(sry);   Session sesion1 = sfy.openSession();   Session sesion2 = sfy.openSession();      System.out.println(sesion1==sesion2);       //  Student student =new Student(3,"周恩来","男",new Date(),"绍兴");//创建学生对象 //  session.save(student);//会话保存学生对象进入数据库  }        @Test  public void testSaveStudent2(){   //获取配置对象，得到hibernate.cfg.xml配置的内容   Configuration config = new Configuration().configure();   //获取服务注册对象，获取hibernate.hbm.xml配置的内容   ServiceRegistry sry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();      SessionFactory sfy = config.buildSessionFactory(sry);   Session sesion1 = sfy.getCurrentSession();   Session sesion2 = sfy.getCurrentSession();      System.out.println(sesion1==sesion2);       //  Student student =new Student(3,"周恩来","男",new Date(),"绍兴");//创建学生对象 //  session.save(student);//会话保存学生对象进入数据库  }

}

demo2

package hibernate_001;

import java.sql.Array; import java.sql.Blob; import java.sql.CallableStatement; import java.sql.Clob; import java.sql.DatabaseMetaData; import java.sql.NClob; import java.sql.PreparedStatement; import java.sql.SQLClientInfoException; import java.sql.SQLException; import java.sql.SQLWarning; import java.sql.SQLXML; import java.sql.Savepoint; import java.sql.Statement; import java.sql.Struct; import java.util.Date; import java.util.Map; import java.util.Properties; import java.util.TimeZone; import java.util.concurrent.Executor;

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.ddwei.student.Student; import com.mysql.jdbc.Connection; import com.mysql.jdbc.ExceptionInterceptor; import com.mysql.jdbc.Extension; import com.mysql.jdbc.MySQLConnection; import com.mysql.jdbc.log.Log;

public class StudentTest2 {    private SessionFactory sessionFactory;  private Session session;  private Transaction trasaction;    @Test  public void testSaveStudent(){   //获取配置对象，得到hibernate.cfg.xml配置的内容   Configuration config = new Configuration().configure();   //获取服务注册对象，获取hibernate.hbm.xml配置的内容   ServiceRegistry sry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();      SessionFactory sfy = config.buildSessionFactory(sry);      Session sesion1 = sfy.openSession();      sesion1.doWork(new Work() {        @Override    public void execute(java.sql.Connection connection) throws SQLException {     // TODO Auto-generated method stub     System.out.println("connection.hashcode is "+connection.hashCode());    }   });      Student student =new Student(4,"周恩来","男",new Date(),"绍兴");//创建学生对象   sesion1.save(student);//会话保存学生对象进入数据库

Session sesion2 = sfy.openSession();   Student student2 =new Student(5,"周恩来","男",new Date(),"绍兴");//创建学生对象   sesion2.doWork(new Work() {        @Override    public void execute(java.sql.Connection connection) throws SQLException {     // TODO Auto-generated method stub     System.out.println("connection.hashcode is "+connection.hashCode());    }   });      sesion2.save(student2);//会话保存学生对象进入数据库

}        @Test  public void testSaveStudent2(){   //获取配置对象，得到hibernate.cfg.xml配置的内容   Configuration config = new Configuration().configure();   //获取服务注册对象，获取hibernate.hbm.xml配置的内容   ServiceRegistry sry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();      SessionFactory sfy = config.buildSessionFactory(sry);   Session sesion1 = sfy.getCurrentSession();   Transaction tran = sesion1.beginTransaction();   Student student =new Student(1,"周恩来","男",new Date(),"绍兴");//创建学生对象   sesion1.doWork(new Work(){    @Override    public void execute(java.sql.Connection connection) throws SQLException {     // TODO Auto-generated method stub     System.out.println("connection.hashcode is "+connection.hashCode());    }   });   sesion1.save(student);//会话保存学生对象进入数据库   tran.commit();         Session sesion2 = sfy.getCurrentSession();   Transaction tran2 = sesion2.beginTransaction();

Student student2 =new Student(2,"周恩来","男",new Date(),"绍兴");//创建学生对象   sesion2.doWork(new Work() {        @Override    public void execute(java.sql.Connection connection) throws SQLException {     // TODO Auto-generated method stub     System.out.println("connection.hashcode is "+connection.hashCode());    }   });   sesion2.save(student2);//会话保存学生对象进入数据库   tran2.commit();     }

}