mybatis-自定义缓存-redis二级缓存

在mybatis一级缓存二级缓存中已经介绍过了二级缓存的大致原理。下面我们用redis来实现一下二级缓存。环境是springmvc+mybatis+redis

步骤一、引入redis相关的maven依赖

<!-- spring-redis实现 -->
<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-redis</artifactId>
    <version>1.6.2.RELEASE</version>
</dependency>
<!-- redis客户端jar -->
<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.8.0</version>
</dependency>

步骤二、新建redis的配置redis.xml,redis.properties

<?xml version="1.0" encoding="utf-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="
            http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.0.xsd"
       default-autowire="byName" default-lazy-init="false">
    <!--redis数据源-->
    <bean id="poolConfig" class="redis.clients.jedis.JedisPoolConfig">
        <property name="maxIdle" value="${redis.maxIdle}"/>
        <property name="maxTotal" value="${redis.maxActive}"/>
        <property name="maxWaitMillis" value="${redis.maxWait}"/>
        <property name="testOnBorrow" value="${redis.testOnBorrow}"/>
    </bean>
    <!--Spring-redis连接池管理工厂-->
    <bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory"
            p:hostName="${redis.host}" p:port="${redis.port}"
            p:password="${redis.pass}" p:poolConfig-ref="poolConfig"/>
    <!-- 使用中间类解决RedisCache.jedisConnectionFactory的静态注入，从而使MyBatis实现第三方缓存 -->
    <bean id="redisCacheTransfer" class="com.yihaomen.mybatis.cache.RedisCacheTransfer">
        <property name="jedisConnectionFactory" ref="jedisConnectionFactory"/>
    </bean>
</beans>

redis.host=192.168.31.55
redis.port=6379
redis.pass=
redis.maxIdle=300
redis.maxActive=600
redis.maxWait=1000
redis.testOnBorrow=true

步骤三、将redis.xml引入到spring的配置文件applicationContext.xml

<bean id="propertyConfigurer"
     class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>classpath*:jdbc.properties</value>
                <value>classpath*:redis.properties</value>
            </list>
        </property>
    </bean>
<import resource="redis.xml"/>

步骤四、创建缓存实现类RedisCache

package com.yihaomen.mybatis.cache;

import org.apache.ibatis.cache.Cache;
import org.springframework.data.redis.connection.jedis.JedisConnection;
import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;
import org.springframework.data.redis.serializer.JdkSerializationRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import redis.clients.jedis.exceptions.JedisConnectionException;

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 *   
 *  @ProjectName: springmvc-mybatis 
 *  @Description: 使用第三方内存数据库Redis作为二级缓存
 *  @author: lisen
 *  @date: 2017/11/8  
 */
public class RedisCache implements Cache{

    private static JedisConnectionFactory jedisConnectionFactory;

    private final String id;

    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    public RedisCache(final String id) {
        if(id == null) {
            throw new IllegalArgumentException("Cache instances require an ID");
        }
        this.id = id;
    }

    public static void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {
        RedisCache.jedisConnectionFactory = jedisConnectionFactory;
    }

    @Override
    public String getId() {
        return this.id;
    }

    public void putObject(Object key, Object value) {
        JedisConnection connection = null;
        try {
            connection = jedisConnectionFactory.getConnection();
            RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer();
            connection.set(serializer.serialize(key), serializer.serialize(value));
        } catch (JedisConnectionException e) {
            e.printStackTrace();
        } finally {
            if(connection != null) {
                connection.close();
            }
        }
    }

    public Object getObject(Object key) {
        Object result = null;
        JedisConnection connection = null;
        try {
            connection = jedisConnectionFactory.getConnection();
            RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer();
            result = serializer.deserialize(connection.get(serializer.serialize(key)));
        } catch (JedisConnectionException e) {
            e.printStackTrace();
        } finally {
            if(connection != null) {
                connection.close();
            }
        }
        return result;
    }

    public Object removeObject(Object key) {
        JedisConnection connection = null;
        Object result = null;
        try {
            connection = jedisConnectionFactory.getConnection();
            RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer();
            result = connection.expire(serializer.serialize(key), 0);
        } catch (JedisConnectionException e) {
            e.printStackTrace();
        } finally {
            if(connection != null) {
                connection.close();
            }
        }
        return result;
    }

    @Override
    public void clear() {
        JedisConnection connection = null;
        try {
            connection = jedisConnectionFactory.getConnection();
            connection.flushDb();
            connection.flushAll();
        } catch (JedisConnectionException e) {
            e.printStackTrace();
        } finally {
            if(connection != null) {
                connection.close();
            }
        }
    }

    public int getSize() {
        int result = 0;
        JedisConnection connection = null;
        try {
            connection = jedisConnectionFactory.getConnection();
            result = Integer.valueOf(connection.dbSize().toString());
        } catch (JedisConnectionException e) {
            e.printStackTrace();
        } finally {
            if(connection != null) {
                connection.close();
            }
        }
        return result;
    }

    public ReadWriteLock getReadWriteLock() {
        return this.readWriteLock;
    }
}

步骤五、 创建中间类RedisCacheTransfer，完成RedisCache.jedisConnectionFactory的静态注入

package com.yihaomen.mybatis.cache;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;

/**
 *   
 *  @ProjectName: springmvc-mybatis 
 *  @Description: 创建中间类RedisCacheTransfer，完成RedisCache.jedisConnectionFactory的静态注入,
 *                静态注入中间类
 *  @author: lisen
 *  @date: 2017/11/8  
 */
public class RedisCacheTransfer {

    @Autowired
    public void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {
        RedisCache.setJedisConnectionFactory(jedisConnectionFactory);
    }
}

步骤六、在mapper(User.xml)中加入MyBatis二级缓存

<?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.yihaomen.mybatis.dao.UserMapper">
    <cache type="com.yihaomen.mybatis.cache.RedisCache"/>

　　<select id="selectUserByID" parameterType="int" resultType="User" >
    　　select * from `user` where id = #{id}
　　</select>

</mapper>

我们还可以配置在SQL层面上的缓存配置，来决定它们是否需要使用或者刷新缓存，我们往往根据两个属性：userCache和flushCache来完成，其中userCache表示是否需要使用缓存，儿flushCache表示插入后是否需要刷新缓存，比如

<select ... flushCache="false" useCache="true"/>

<insert ... flushCache="true"/>

<update... flushCache="true"/>

<delete... flushCache="true"/>

步骤七、在mybatis-config.xml文件中开启二级缓存

<settings>
        <!--这个配置使全局的映射器(二级缓存)启用或禁用缓存-->
        <setting name="cacheEnabled" value="true" />
</setting>

步骤八、单元测试

package com.yihaomen.service.test;

import com.yihaomen.mybatis.dao.UserMapper;
import com.yihaomen.mybatis.model.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import java.util.List;

/**
 *   
 *  @ProjectName: springmvc-mybatis 
 *  @Description:
 *  @author: lisen
 *  @date: 2017/11/9  
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:applicationContext.xml"})
public class UserSpringTest {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void selectUserById() {
        List<User> users = userMapper.selectUserById(11L);
    }

}

https://gitee.com/huayicompany/springmvc-mybatis

参考：

[1]博客，http://blog.csdn.net/xiadi934/article/details/50786293