get 会使用二级缓存

经常看到session.get()和session.load()方法的区别，书上说load方法可以充分利用二级缓存中的现有数据，而get方法仅在内部缓存进行数据查找，如果没有查找到数据，将越过二级缓存，直接调用SQL完成数据读取。可我试了试，执行结果确实两个方法都充分利用了二级缓存。
代码如下：
  TuserDAO

  package org.xiyou;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Expression;

public class TuserDAO {
     public void get()
  {
      SessionFactory sessionFactory=new Configuration().configure("org/xiyou/hibernate.cfg.xml").buildSessionFactory();
      Session session=sessionFactory.openSession();
      Tuser user=(Tuser)session.get(Tuser.class, new Integer(3));
      System.out.println(user.getName());
      session.close();
      Session session1=sessionFactory.openSession();
      Tuser user1=(Tuser)session1.get(Tuser.class, new Integer(3));
      System.out.println(user1.getName());
      System.out.println((session.equals(session1)));
      session1.close();
  }
  /*
   * 测试Session.load()
   *
   *
   * */
  public void load()
  {
      SessionFactory sessionFactory=new Configuration().configure("org/xiyou/hibernate.cfg.xml").buildSessionFactory();
      Session session=sessionFactory.openSession();
      Tuser user=(Tuser)session.load(Tuser.class, new Integer(3));
      System.out.println(user.getName());
      session.close();
      Session session1=sessionFactory.openSession();
      Tuser user1=(Tuser)session1.load(Tuser.class, new Integer(3));

      System.out.println(user1.getName());

      session1.close();
      System.out.println((session.equals(session1)));
  }
}

测试类：

package org.xiyou;

public class Test01 {
   public static void main(String [] args)
   {
       TuserDAO userdao=new TuserDAO();
       userdao.get2();
       userdao.load();
    }
}

Java代码 

Hibernate: select tuser0_.id as id0_, tuser0_.version as version0_0_, tuser0_.name as name0_0_ from test.tuser tuser0_ where tuser0_.id=?
aaaa
aaaa
false
aaaa
aaaa
false

hibernate.cfg.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">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
    <property name="dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="connection.url">
        jdbc:mysql://localhost/test
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password">123</property>
    <property name="connection.driver_class">
        com.mysql.jdbc.Driver
    </property>
    <property name="myeclipse.connection.profile">mysql</property>
    <property name="show_sql">true</property>
<property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
    <mapping resource="org/xiyou/Tuser.hbm.xml" />

</session-factory>

</hibernate-configuration>

<?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">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
	<property name="dialect">
		org.hibernate.dialect.MySQLDialect
	</property>
	<property name="connection.url">
		jdbc:mysql://localhost/test
	</property>
	<property name="connection.username">root</property>
	<property name="connection.password">123</property>
	<property name="connection.driver_class">
		com.mysql.jdbc.Driver
	</property>
	<property name="myeclipse.connection.profile">mysql</property>
	<property name="show_sql">true</property>
<property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
	<mapping resource="org/xiyou/Tuser.hbm.xml" />

</session-factory>

</hibernate-configuration>

Tuser.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
    <class name="org.xiyou.Tuser" table="tuser" catalog="test" >
    <cache usage="read-only"/>
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="version"
                 column="version"
                 type="integer"></property>
        <property name="name" type="java.lang.String">
            <column name="name" length="20" />
        </property>

    </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
    <class name="org.xiyou.Tuser" table="tuser" catalog="test" >
    <cache usage="read-only"/>
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="version"
                 column="version"
                 type="integer"></property>
        <property name="name" type="java.lang.String">
            <column name="name" length="20" />
        </property>

    </class>
</hibernate-mapping>

ehcache.xml

Java代码

<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="ehcache.xsd">
    <diskStore path="java.io.tmpdir" />
    <defaultCache
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="120"
        timeToLiveSeconds="120"
        overflowToDisk="true"
        diskPersistent="false"
        diskExpiryThreadIntervalSeconds="120"
        memoryStoreEvictionPolicy="LRU" />
</ehcache>

 

 

 

 

源码（3.2.6.ga），确实如此

先看一下Session的默认实现SessionImpl
get方法会转到fireLoad，loadType的值是LoadEventListener.GET
load方法也是转到fireLoad，不同的是loadType的值是LoadEventListener.LOAD

private void fireLoad(LoadEvent event, LoadType loadType) {
    errorIfClosed();
    checkTransactionSynchStatus();
    LoadEventListener[] loadEventListener = listeners.getLoadEventListeners();
    for ( int i = 0; i < loadEventListener.length; i++ ) {
        loadEventListener[i].onLoad(event, loadType);
    }
}

private void fireLoad(LoadEvent event, LoadType loadType) {
	errorIfClosed();
	checkTransactionSynchStatus();
	LoadEventListener[] loadEventListener = listeners.getLoadEventListeners();
	for ( int i = 0; i < loadEventListener.length; i++ ) {
		loadEventListener[i].onLoad(event, loadType);
	}
}

 调用loadEventListener的onLoad方法
LoadEventListener的默认实现DefaultLoadEventListener中
最终会转到doLoad方法，options就是前面的loadType

protected Object doLoad(
            final LoadEvent event,
            final EntityPersister persister,
            final EntityKey keyToLoad,
            final LoadEventListener.LoadType options) throws HibernateException {
    。。。。。。
    Object entity = loadFromSessionCache( event, keyToLoad, options );//从一级缓存加载
    //如果不为空，直接返回
    。。。。。。
    entity = loadFromSecondLevelCache(event, persister, options);//从二级缓存加载
    。。。。。。
}

protected Object doLoad(
			final LoadEvent event,
			final EntityPersister persister,
			final EntityKey keyToLoad,
			final LoadEventListener.LoadType options) throws HibernateException {
	。。。。。。
	Object entity = loadFromSessionCache( event, keyToLoad, options );//从一级缓存加载
	//如果不为空，直接返回
	。。。。。。
	entity = loadFromSecondLevelCache(event, persister, options);//从二级缓存加载
	。。。。。。
}

 loadFromSecondLevelCache即是从二级缓存中查找对象
get和load的区别在于LoadEventListener.LoadType options参数，一个是LoadEventListener.GET，一个是LoadEventListener.LOAD
而在这个方法中，并没有用到options参数
也就是说get和load使用二级缓存的状况是一样的，get也会使用二级缓存