hibernate（六）之一级缓存、二级缓存案例

1.要实现二级缓存，需另加以下jar包：

   ehcache-core-2.4.3.jar、hibernate-core-4.2.3.Final.jar、slf4j-api-1.6.6.jar

2.需要更改配置文件

   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">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://127.0.0.1:3306/hibernate_db</property>
        <property name="connection.username">root</property>
        <property name="connection.password">beanGou</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

  <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>
        <property name="hibernate.cache.provider_configuration_file_resource_path">ehcache2.xml</property>
       
        <!-- 产生统计信息 -->
        <property name="generate_statistics">true</property>
        <!-- Disable the second-level cache  -->
        <!--<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
  
  --><!--<property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
        --><!--<class-cache class="com.sinoi.domain.Employee" usage="read-only"/>
       
  --><property name="format_sql">true</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
       
        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="com/sinoi/domain/Department.hbm.xml"/>
  <mapping resource="com/sinoi/domain/Employee.hbm.xml"/>
    </session-factory>

</hibernate-configuration>

   如果要给某个类设置二级缓存，则相应的改其配置文件，如

  Employee.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">

<hibernate-mapping package="com.sinoi.domain">

    <class name="Employee" table="hib_employee">
        <cache usage="read-only"/>
        <id name="id" column="EMPLOYEE_ID">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <!--<many-to-one name="department" column="department_id" not-null="false"></many-to-one>
    --></class>

</hibernate-mapping>

3.测试代码

@Test
	public void get() {
		Session session = HibernateUtil.getSession();
		Employee employee = (Employee) session.get(Employee.class, 1);
		employee = (Employee) session.get(Employee.class, 1);
		System.out.println(employee.getName());
		session.evict(employee);
	
		employee = (Employee) session.get(Employee.class, 1);
		session.close();
		Statistics statistics = HibernateUtil.getSessionFactory().getStatistics();
		System.out.println(statistics);
		System.out.println("命中数：" + statistics.getSecondLevelCacheHitCount());
		System.out.println("错过数：" + statistics.getSecondLevelCacheMissCount());
		System.out.println("放入数：" + statistics.getSecondLevelCachePutCount());
	}

注：增加了HibernateUtil类以及getSessionFactory方法

package com.sinoi.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
	private static SessionFactory factory;
	private static Session session;

	private HibernateUtil() {
	}

	public static SessionFactory getSessionFactory() {
		if (factory == null) {
			factory = new Configuration().configure().buildSessionFactory();
		}
		return factory;
	}
	
	public static Session getSession() {
		if (session == null) {
			return getSessionFactory().openSession();
		} else {
			return session;
		}
	}
}