二級緩存是多個SqlSession共享的，其作用域是mapper的同一個namespace，不同的sqlSession兩次執(zhí)行相同namespace下的sql語句且向sql中傳遞參數(shù)也相同即最終執(zhí)行相同的sql語句，第一次執(zhí)行完畢會將數(shù)據(jù)庫中查詢的數(shù)據(jù)寫到緩存（內(nèi)存），第二次會從緩存中獲取數(shù)據(jù)將不再從數(shù)據(jù)庫查詢，從而提高查詢效率。Mybatis默認(rèn)沒有開啟二級緩存需要在setting全局參數(shù)中配置開啟二級緩存。
下面是使用Ehcache來作為Mybatis二級緩存的實(shí)例：
application.properties開啟mybatis中二級緩存
==mybatis.configuration.cache-enabled=true==
默認(rèn)二級緩存是開啟的
server.port=80
# 數(shù)據(jù)源配置
spring.datasource.url=jdbc:mysql://localhost:3306/ssb_test
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=root
#連接池配置
#spring.datasource.type=org.apache.commons.dbcp2.BasicDataSource
#mybatis
#entity掃描的包名
mybatis.type-aliases-package=com.xiaolyuh.domain.model
#Mapper.xml所在的位置
mybatis.mapper-locations=classpath*:/mybaits/*Mapper.xml
#開啟MyBatis的二級緩存
mybatis.configuration.cache-enabled=true
#pagehelper
pagehelper.helperDialect=mysql
pagehelper.reasonable=true
pagehelper.supportMethodsArguments=true
pagehelper.params=count=countSql
#日志配置
logging.level.com.xiaolyuh=debug
logging.level.org.springframework.web=debug
logging.level.org.springframework.transaction=debug
logging.level.org.mybatis=debug
debug=false
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>spring-boot-student-mybatis-ehcache</artifactId>
<packaging>jar</packaging>
<name>spring-boot-student-mybatis-ehcache</name>
<description>Demo Mybatis ehcache for Spring Boot</description>
<parent>
<groupId>com.xiaolyuh</groupId>
<artifactId>spring-boot-student</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath />
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.0</version>
</dependency>
<!--pagehelper -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.31</version>
</dependency>
<dependency>
<groupId>net.sf.ehcache</groupId>
<artifactId>ehcache</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-ehcache</artifactId>
<version>1.0.0</version>
</dependency>
</dependencies>
</project>
Ehcache配置
在src\main\resources目錄下創(chuàng)建ehcache.xml文件，內(nèi)容如下：
<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
<!--
http://www.cnblogs.com/lzy1991/p/5335249.html
http://www.cnblogs.com/little-fly/p/6251439.html
緩存配置
diskStore：指定數(shù)據(jù)在磁盤中的存儲位置。
name:緩存名稱。
defaultCache：當(dāng)借助CacheManager.add("demoCache")創(chuàng)建Cache時，EhCache便會采用<defalutCache/>指定的的管理策略,以下屬性是必須的：
maxElementsInMemory：緩存最大個數(shù)。
eternal:對象是否永久有效，一但設(shè)置了，timeout將不起作用。
timeToIdleSeconds：設(shè)置對象在失效前的允許閑置時間（單位：秒）。僅當(dāng)eternal=false對象不是永久有效時使用，可選屬性，默認(rèn)值是0，也就是可閑置時間無窮大。
timeToLiveSeconds：設(shè)置對象在失效前允許存活時間（單位：秒）。最大時間介于創(chuàng)建時間和失效時間之間。僅當(dāng)eternal=false對象不是永久有效時使用，默認(rèn)是0.，也就是對象存活時間無窮大。
overflowToDisk：當(dāng)內(nèi)存中對象數(shù)量達(dá)到maxElementsInMemory時，Ehcache將會對象寫到磁盤中。
diskSpoolBufferSizeMB：這個參數(shù)設(shè)置DiskStore（磁盤緩存）的緩存區(qū)大小。默認(rèn)是30MB。每個Cache都應(yīng)該有自己的一個緩沖區(qū)。
maxElementsOnDisk：硬盤最大緩存?zhèn)€數(shù)。
diskPersistent：是否緩存虛擬機(jī)重啟期數(shù)據(jù) Whether the disk store persists between restarts of the Virtual Machine. The default value is false.
diskExpiryThreadIntervalSeconds：磁盤失效線程運(yùn)行時間間隔，默認(rèn)是120秒。
memoryStoreEvictionPolicy：當(dāng)達(dá)到maxElementsInMemory限制時，Ehcache將會根據(jù)指定的策略去清理內(nèi)存。默認(rèn)策略是LRU（最近最少使用）。你可以設(shè)置為FIFO（先進(jìn)先出）或是LFU（較少使用）。
clearOnFlush：內(nèi)存數(shù)量最大時是否清除。
-->
<diskStore path="e:\ehcache" />
<defaultCache
maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="120"
timeToLiveSeconds="120"
overflowToDisk="true"
maxElementsOnDisk="10000000"
diskPersistent="false"
diskExpiryThreadIntervalSeconds="120"
memoryStoreEvictionPolicy="LRU"
/>
</ehcache>
Mapper文件
<cache /> 添加這個節(jié)點(diǎn)會默認(rèn)將該namespace下所有的的select語句緩存。如果不需要進(jìn)行緩存，需要設(shè)置useCache="false"。
<select id="findByPage" resultMap="BaseResultMap" useCache="false">
完整的Mapper文件，如下：
<?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.xiaolyuh.domain.mapper.PersonMapper">
<!--mybatis ehcache緩存配置 -->
<!-- 以下兩個<cache>標(biāo)簽二選一,第一個可以輸出日志,第二個不輸出日志 -->
<!--<cache type="org.mybatis.caches.ehcache.LoggingEhcache" />
<cache type="org.mybatis.caches.ehcache.EhcacheCache"/>-->
<!--根據(jù)需求調(diào)整緩存參數(shù)：-->
<cache type="org.mybatis.caches.ehcache.EhcacheCache">
<property name="timeToIdleSeconds" value="3600"/>
<property name="timeToLiveSeconds" value="3600"/>
<!-- 同ehcache參數(shù)maxElementsInMemory -->
<property name="maxEntriesLocalHeap" value="1000"/>
<!-- 同ehcache參數(shù)maxElementsOnDisk -->
<property name="maxEntriesLocalDisk" value="10000000"/>
<property name="memoryStoreEvictionPolicy" value="LRU"/>
</cache>
<resultMap id="BaseResultMap" type="com.xiaolyuh.domain.model.Person">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
<id column="id" property="id" jdbcType="BIGINT"/>
<result column="name" property="name" jdbcType="VARCHAR"/>
<result column="age" property="age" jdbcType="INTEGER"/>
<result column="address" property="address" jdbcType="VARCHAR"/>
</resultMap>
<sql id="Base_Column_List">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
id, name, age, address
</sql>
<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
select
<include refid="Base_Column_List"/>
from person
where id = #{id,jdbcType=BIGINT}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
delete from person
where id = #{id,jdbcType=BIGINT}
</delete>
<insert id="insert" parameterType="com.xiaolyuh.domain.model.Person">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
<selectKey resultType="java.lang.Long" keyProperty="id" order="AFTER">
SELECT LAST_INSERT_ID()
</selectKey>
insert into person (name, age, address
)
values (#{name,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER}, #{address,jdbcType=VARCHAR}
)
</insert>
<insert id="insertSelective" parameterType="com.xiaolyuh.domain.model.Person">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
<selectKey resultType="java.lang.Long" keyProperty="id" order="AFTER">
SELECT LAST_INSERT_ID()
</selectKey>
insert into person
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="name != null">
name,
</if>
<if test="age != null">
age,
</if>
<if test="address != null">
address,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides=",">
<if test="name != null">
#{name,jdbcType=VARCHAR},
</if>
<if test="age != null">
#{age,jdbcType=INTEGER},
</if>
<if test="address != null">
#{address,jdbcType=VARCHAR},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.xiaolyuh.domain.model.Person">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
update person
<set>
<if test="name != null">
name = #{name,jdbcType=VARCHAR},
</if>
<if test="age != null">
age = #{age,jdbcType=INTEGER},
</if>
<if test="address != null">
address = #{address,jdbcType=VARCHAR},
</if>
</set>
where id = #{id,jdbcType=BIGINT}
</update>
<update id="updateByPrimaryKey" parameterType="com.xiaolyuh.domain.model.Person">
<!--
WARNING - @mbggenerated
This element is automatically generated by MyBatis Generator, do not modify.
-->
update person
set name = #{name,jdbcType=VARCHAR},
age = #{age,jdbcType=INTEGER},
address = #{address,jdbcType=VARCHAR}
where id = #{id,jdbcType=BIGINT}
</update>
<!-- 對這個語句useCache="true"默認(rèn)是true，可以不寫 -->
<select id="findAll" resultMap="BaseResultMap" useCache="true">
select
<include refid="Base_Column_List"/>
from person
</select>
<!-- 對這個語句禁用二級緩存 -->
<select id="findByPage" resultMap="BaseResultMap" useCache="false">
select
<include refid="Base_Column_List"/>
from person
</select>
</mapper>
實(shí)體類
package com.xiaolyuh.domain.model;
import java.io.Serializable;
public class Person implements Serializable {
private Long id;
/**
* 名稱
*/
private String name;
/**
* 年齡
*/
private Integer age;
/**
* 地址
*/
private String address;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
Mapper-類
package com.xiaolyuh.domain.mapper;
import com.github.pagehelper.Page;
import com.xiaolyuh.domain.model.Person;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;
@Mapper//聲明成mybatis Dao層的Bean，也可以在配置類上使用@MapperScan("com.xiaolyuh.domain.mapper")注解聲明
public interface PersonMapper {
int deleteByPrimaryKey(Long id);
int insert(Person record);
int insertSelective(Person record);
Person selectByPrimaryKey(Long id);
int updateByPrimaryKeySelective(Person record);
int updateByPrimaryKey(Person record);
/**
* 獲取所有數(shù)據(jù)
* @return
*/
List<Person> findAll();
/**
* 分頁查詢數(shù)據(jù)
* @return
*/
Page<Person> findByPage();
}
Severice接口類
package com.xiaolyuh.service;
import com.github.pagehelper.Page;
import com.xiaolyuh.domain.model.Person;
import java.util.List;
/**
* Created by yuhao.wang on 2017/6/19.
*/
public interface PersonService {
List<Person> findAll();
/**
* 分頁查詢
* @param pageNo 頁號
* @param pageSize 每頁顯示記錄數(shù)
* @return
*/
Page<Person> findByPage(int pageNo, int pageSize);
void insert(Person person);
}
Severice實(shí)現(xiàn)類
package com.xiaolyuh.service.impl;
import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.xiaolyuh.domain.mapper.PersonMapper;
import com.xiaolyuh.domain.model.Person;
import com.xiaolyuh.service.PersonService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
/**
* Created by yuhao.wang on 2017/6/19.
*/
@Service
@Transactional(readOnly = true)
public class PersonServiceImpl implements PersonService {
@Autowired
private PersonMapper personMapper;
@Override
public List<Person> findAll() {
return personMapper.findAll();
}
@Override
public Page<Person> findByPage(int pageNo, int pageSize) {
PageHelper.startPage(pageNo, pageSize);
return personMapper.findByPage();
}
@Override
@Transactional
public void insert(Person person) {
personMapper.insert(person);
}
}
測試類
package com.xiaolyuh;
import com.github.pagehelper.Page;
import com.xiaolyuh.domain.model.Person;
import com.xiaolyuh.service.PersonService;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import com.alibaba.fastjson.JSON;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class PersonMapperTests {
private Logger logger = LoggerFactory.getLogger(PersonMapperTests.class);
@Autowired
private PersonService personService;
@Before
public void testInsert() {
Person person = new Person();
person.setName("測試");
person.setAddress("address");
person.setAge(10);
personService.insert(person);
Assert.assertNotNull(person.getId());
logger.debug(JSON.toJSONString(person));
}
@Test
public void testFindAll() {
List<Person> persons = personService.findAll();
Assert.assertNotNull(persons);
logger.debug(JSON.toJSONString(persons));
}
@Test
public void testFindByPage() {
Page<Person> persons = personService.findByPage(1, 2);
Assert.assertNotNull(persons);
logger.debug(persons.toString());
logger.debug(JSON.toJSONString(persons));
}
@Test
public void testCacheByPage() {
long begin = System.currentTimeMillis();
List<Person> persons = personService.findAll();
long ing = System.currentTimeMillis();
personService.findAll();
long end = System.currentTimeMillis();
logger.debug("第一次請求時間：" + (ing - begin) + "ms");
logger.debug("第二次請求時間:" + (end - ing) + "ms");
Assert.assertNotNull(persons);
logger.debug(persons.toString());
logger.debug(JSON.toJSONString(persons));
}
}
執(zhí)行測試類，打印日志信息
Cache Hit Ratio [com.xiaolyuh.domain.mapper.PersonMapper]: 0.5
2017-06-28 10:15:32.214 DEBUG 10472 --- [ main] org.mybatis.spring.SqlSessionUtils : Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3f6c2763]
2017-06-28 10:15:32.214 DEBUG 10472 --- [ main] org.mybatis.spring.SqlSessionUtils : Transaction synchronization committing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3f6c2763]
2017-06-28 10:15:32.214 DEBUG 10472 --- [ main] org.mybatis.spring.SqlSessionUtils : Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3f6c2763]
2017-06-28 10:15:32.214 DEBUG 10472 --- [ main] org.mybatis.spring.SqlSessionUtils : Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3f6c2763]
2017-06-28 10:15:32.223 DEBUG 10472 --- [ main] com.xiaolyuh.PersonMapperTests : 第一次請求時間：26ms
2017-06-28 10:15:32.223 DEBUG 10472 --- [ main] com.xiaolyuh.PersonMapperTests : 第二次請求時間:11ms
源碼
https://github.com/wyh-spring-ecosystem-student/spring-boot-student/tree/releases
spring-boot-student-mybatis-ehcache工程
