Mybatis整合第三方缓存ehcache

怼烎@ 2022-04-15 00:37 356阅读 0赞

第三方缓存主要是来壮大Mybatis的二级缓存。

### Mybatis整合第三方缓存原理图： ###

### ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70][] ###

**解读：**

1、客户从数据库获取数据视为一次会话，抽象为sqlSession对象

2、一个Excutor包含增删改查的操作；

3、CachingExcutor是对Excutor的包装，此处相当于代理模式

4、当有会话时，先访问CachingExcutor对象，CachingExcutor先从二级缓存查找数据，如果有就直接返回；如果没有，就进入Excutor的一级缓存，如果还是没有就执行Excutor的增删改查返回结果，并将结果保存至缓存中，同一个sqlSession再次访问就可以从一级缓存中取了；

5、由于mybatis的缓存只用了map实现，所以mybatis允许缓存由第三方缓存来实现，并定义了cache接口，第三方只要实现该接口即可，和mybatis整合在一起后由mybatis在程序中进行调用；

### 一、下载相关jar包 ###

**1、下载ehcache源码包**

下载地址：[https://mvnrepository.com/artifact/net.sf.ehcache/ehcache-core/2.6.8][https_mvnrepository.com_artifact_net.sf.ehcache_ehcache-core_2.6.8]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 1][]

或者，用maven导入：

<dependency>
        <groupId>net.sf.ehcache</groupId>
        <artifactId>ehcache-core</artifactId>
        <version>2.6.8</version>
    </dependency>

如图：

![2018111916160058.png][]

**2、下载其依赖的日志包sl4j**

2.1  下载[slf4j-ap][]i.jar包

[https://mvnrepository.com/artifact/org.slf4j/slf4j-api/1.7.25][slf4j-ap]

或者maven配置：

<dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.25</version>
    </dependency>

2.2 下载slf4j-log4j12.jar包

[https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12][https_mvnrepository.com_artifact_org.slf4j_slf4j-log4j12]

或者maven配置：

<dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.25</version>
        <scope>test</scope>
    </dependency>

如图：

![20181119161545248.png][]

**3、下载mybatis和ehcache的适配包**

方式一：github上下载

[https://github.com/mybatis/ehcache-cache/releases][https_github.com_mybatis_ehcache-cache_releases]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 2][]

方式二：maven仓库中下载

[https://mvnrepository.com/artifact/org.mybatis.caches/mybatis-ehcache/1.0.3][https_mvnrepository.com_artifact_org.mybatis.caches_mybatis-ehcache_1.0.3]

方式三：maven配置自动导入

<dependency>
        <groupId>org.mybatis.caches</groupId>
        <artifactId>mybatis-ehcache</artifactId>
        <version>1.0.3</version>
    </dependency>

如图：

![20181119162137470.png][]

**4、还需要一个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:\44\ehcache" />
     
     <defaultCache 
       maxElementsInMemory="1" 
       maxElementsOnDisk="10000000"
       eternal="false" 
       overflowToDisk="true" 
       timeToIdleSeconds="120"
       timeToLiveSeconds="120" 
       diskExpiryThreadIntervalSeconds="120"
       memoryStoreEvictionPolicy="LRU">
     </defaultCache>
    </ehcache>

### 二、整合mybatis ###

**1、将准备好的jar包和xml导入到项目中**

![20181119163158663.png][]

![20181119163116205.png][]

**2、mapper.xml中使用自定义缓存**

<?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="com.atguigu.mybatis.dao.EmployeeMapper">
    
    	<cache type="org.mybatis.caches.ehcache.EhcacheCache"></cache>
    
     	
     	<select id="getEmpByLastNameLikeReturnMap" resultType="com.atguigu.mybatis.bean.Employee">
     		select * from tbl_employee where last_name like #{lastName}
     	</select>
    </mapper>

**3、测试**

@Test
    public void testSecondLevelCache() throws IOException{
    	SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
    	SqlSession openSession = sqlSessionFactory.openSession();
    	SqlSession openSession2 = sqlSessionFactory.openSession();
    	try{
    
    		EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
    		EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);
    		
    		Employee emp01 = mapper.getEmpById(1);
    		System.out.println(emp01);
    		openSession.close();
    		
    		//第二次查询是从二级缓存中拿到的数据，并没有发送新的sql
    		Employee emp02 = mapper2.getEmpById(1);
    		System.out.println(emp02);
    		openSession2.close();
    		
    	}finally{
    		
    	}
    }

**结果：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 3][]

**说明：**只查询了一次sql，所以第二次访问是从ehcache缓存中拿的，

并且在D:\\44\\ehcache目录下也会有相关数据：

![20181119164335720.png][]

***注: 如果其他mapper.xml需要使用缓存，可进行引用mapper***

<cache-ref namespace="com.atguigu.mybatis.dao.EmployeeMapper"/>

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![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 5][]

或可一试哦！

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70]: /images/20220415/9e0aa72cc60345aabd3ceefab6b144d9.png
[https_mvnrepository.com_artifact_net.sf.ehcache_ehcache-core_2.6.8]: https://mvnrepository.com/artifact/net.sf.ehcache/ehcache-core/2.6.8
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 1]: /images/20220415/699325f874064fb0913b9ed07221116f.png
[2018111916160058.png]: /images/20220415/7fd799ec7e274202927cb79b6191b08b.png
[slf4j-ap]: https://mvnrepository.com/artifact/org.slf4j/slf4j-api/1.7.25
[https_mvnrepository.com_artifact_org.slf4j_slf4j-log4j12]: https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12
[20181119161545248.png]: /images/20220415/d7f2fd5017e149ed8022d348bbc86913.png
[https_github.com_mybatis_ehcache-cache_releases]: https://github.com/mybatis/ehcache-cache/releases
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 2]: /images/20220415/47553f03e090473e839c7bbde2de14bf.png
[https_mvnrepository.com_artifact_org.mybatis.caches_mybatis-ehcache_1.0.3]: https://mvnrepository.com/artifact/org.mybatis.caches/mybatis-ehcache/1.0.3
[20181119162137470.png]: /images/20220415/80630bbc60aa4a1095e7a6850ed49f1e.png
[20181119163158663.png]: /images/20220415/3a1fa9f772204d10bcccd7c7a06c2513.png
[20181119163116205.png]: /images/20220415/4b8eb8be4df443f2b6456f05b1db7615.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 3]: /images/20220415/4adcb974a41946e4a4583b9b7ac7b883.png
[20181119164335720.png]: /images/20220415/c0f7733a63014bfb89e4342ce2a203a2.png
[Java]: https://www.javaxxbj.com/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 4]: /images/20220415/ac4c99ef5d80437ca9e17756c1b0d411.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 5]: /images/20220415/c3a74c345c544ea782028fdf7c588f7e.png