前面几篇文章剖析了mybatis的缓存原理，发现mybatis提供的缓存是非常简陋的，用HashMap进行存储。
有专业做缓存的，那么就使用专业的缓存框架吧，这里使用Ehcache来作为mybatis的缓存。
1.引入jar
<!-- 添加Ehcache核心包 -->
<dependency>
<groupId>net.sf.ehcache</groupId>
<artifactId>ehcache-core</artifactId>
<version>2.6.10</version>
</dependency>
<!-- mybatis整合Ehcache的适配器 -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-ehcache</artifactId>
<version>1.0.0</version>
</dependency>
<!-- 引入日志包 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.6</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
2.引入ehcache.xml文件
添加ehcache.xml
<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
<diskStore path="D:\mybatis\ehcache"/>
<!--
Mandatory Default Cache configuration. These settings will be applied to caches
created programmtically using CacheManager.add(String cacheName)
-->
<!--
name:缓存名称。
maxElementsInMemory：缓存最大个数。
eternal:对象是否永久有效，一但设置了，timeout将不起作用。
timeToIdleSeconds：设置对象在失效前的允许闲置时间（单位：秒）。仅当eternal=false对象不是永久有效时使用，可选属性，默认值是0，也就是可闲置时间无穷大。
timeToLiveSeconds：设置对象在失效前允许存活时间（单位：秒）。最大时间介于创建时间和失效时间之间。仅当eternal=false对象不是永久有效时使用，默认是0.，也就是对象存活时间无穷大。
overflowToDisk：当内存中对象数量达到maxElementsInMemory时，Ehcache将会对象写到磁盘中。
diskSpoolBufferSizeMB：这个参数设置DiskStore（磁盘缓存）的缓存区大小。默认是30MB。每个Cache都应该有自己的一个缓冲区。
maxElementsOnDisk：硬盘最大缓存个数。
diskPersistent：是否缓存虚拟机重启期数据 Whether the disk store persists between restarts of the Virtual Machine. The default value is false.
diskExpiryThreadIntervalSeconds：磁盘失效线程运行时间间隔，默认是120秒。
memoryStoreEvictionPolicy：当达到maxElementsInMemory限制时，Ehcache将会根据指定的策略去清理内存。默认策略是LRU（最近最少使用）。你可以设置为FIFO（先进先出）或是LFU（较少使用）。
clearOnFlush：内存数量最大时是否清除。
-->
<defaultCache
maxElementsInMemory="10"
eternal="false"
timeToIdleSeconds="120"
timeToLiveSeconds="120"
overflowToDisk="true"
maxElementsOnDisk="10000000"
diskPersistent="false"
diskExpiryThreadIntervalSeconds="120"
memoryStoreEvictionPolicy="LRU"
/>
</ehcache>
3.创建示例
package org.mybatis.cache3ehcache;
public class Employee {
private Integer id;
private String lastName;
private String email;
private String gender;
public Employee() {
}
public Employee(Integer id, String lastName, String email, String gender) {
this.id = id;
this.lastName = lastName;
this.email = email;
this.gender = gender;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String toString() {
return "Employee [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", gender=" + gender + "]";
}
}
package org.mybatis.cache3ehcache;
public interface EmployeeMapper {
public Employee getEmpById(Integer id);
}
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.mybatis.cache3ehcache.EmployeeMapper">
<!--这里引用第三方缓存（或自定义缓存）-->
<cache type="org.mybatis.caches.ehcache.EhcacheCache"></cache>
<select id="getEmpById" resultType="org.mybatis.cache3ehcache.Employee" useCache="true">
select * from mybatis_employee me where me.id ={id}
</select>
</mapper>
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="db.properties"></properties>
<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/>
<setting name="lazyLoadingEnabled" value="true" />
<setting name="aggressiveLazyLoading" value="false"/>
<!--开启缓存-->
<setting name="cacheEnabled" value="true"/>
</settings>
<typeAliases>
<!-- 为包下的所有类起别名，默认为类名大小写（不区分大小写） -->
<package name="org.mybatis.cache3ehcache"/>
</typeAliases>
<!-- 默认development是开发环境，如果改成test则表示使用测试环境 -->
<environments default="dev_mysql">
<environment id="dev_mysql">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${mysql.driver}" />
<property name="url" value="${mysql.url}" />
<property name="username" value="${mysql.username}" />
<property name="password" value="${mysql.password}" />
</dataSource>
</environment>
<environment id="test_mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${mysql.drivertest}" />
<property name="url" value="${mysql.urltest}" />
<property name="username" value="${mysql.usernametest}" />
<property name="password" value="${mysql.passwordtest}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mapper/cache3ehcachemapper.xml"/>
</mappers>
</configuration>
测试类：
package org.mybatis.cache3ehcache;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
/**
* 整个Ehcache
* @author DDKK.COM 弟弟快看，程序员编程资料站
*/
public class MybatisTest {
@Test
public void testMybatis() {
String resource = "mybatis-config-cache3ehcache.xml";//全局配置文件
InputStream inputStream = null;
SqlSessionFactory sqlSessionFactory = null;
try {
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession1 = sqlSessionFactory.openSession();
EmployeeMapper mapper1 = sqlSession1.getMapper(EmployeeMapper.class);
Employee emp1 = mapper1.getEmpById(2);
System.out.println(emp1);
sqlSession1.close();
System.out.println("######");
SqlSession sqlSession2 = sqlSessionFactory.openSession();
EmployeeMapper mapper2 = sqlSession2.getMapper(EmployeeMapper.class);
Employee emp2 = mapper2.getEmpById(2);
System.out.println(emp2);
sqlSession2.close();
System.out.println(emp1 == emp2);
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
}
运行结果：
两个不同的sqlSession，发送了一个sql查询，说明缓存已经生效。