使用Redis做Mybatis二级缓存

介绍

1. 使用mybatis时可以使用二级缓存提高查询速度，进而改善用户体验。
2. 使用redis做mybatis的二级缓存可是内存可控<如将单独的服务器部署出来用于二级缓存>，管理方便。

相关jar包

jedis-2.9.0.jar  
spring-data-commons-1.13.7.RELEASE.jar
spring-data-keyvalue-1.2.7.RELEASE.jar
spring-data-redis-1.8.7.RELEASE.jar

使用思路

1. 配置redis.xml 设置redis服务连接各参数
2. 在配置文件中使用 标签，设置开启二级缓存
3. 在mapper.xml 中使用 将cache映射到指定的RedisCacheClass类中
4. 映射类RedisCacheClass 实现 MyBatis包中的Cache类，并重写其中各方法

• 在重写各方法体中，使用redisFactory和redis服务建立连接，将缓存的数据加载到指定的redis内存中(putObject方法)或将redis服务中的数据从缓存中读取出来(getObject方法)；

• 在redis服务中写入和加载数据时需要借用spring-data-redis.jar中JdkSerializationRedisSerializer.class中的序列化(serialize)和反序列化方法(deserialize),此为包中封装的redis默认的序列化方法

5. 映射类中的各方法重写完成后即可实现mybatis数据二级缓存到redis服务中

代码实践

1. 在springmvc.xml 中配置redis相关配置、或者直接写redis.xml

<?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:p="http://www.springframework.org/schema/p"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:task="http://www.springframework.org/schema/task"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/tx 
http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-3.0.xsd" >

<!-- enable autowire -->

 <context:annotation-config /> 

<task:annotation-driven/>

<context:component-scan base-package="demo.util,demo.salesorder,demo.person" />
<!-- Configures the @Controller programming model 必须加上这个，不然请求controller时会出现no mapping url错误-->
<mvc:annotation-driven />
<!-- 引入数据库配置文件 -->
<bean id="propertyConfigurer"    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <list>
            <value>classpath:sysconfig/jdbc.properties</value>
            <value>classpath:sysconfig/redis.properties</value>
        </list>
    </property>
</bean>
<!-- JDBC -->
<bean id="defaultDataSource"   class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"
    p:driverClassName="${jdbc.driverClassName}"
    p:url="${jdbc.databaseurl}"
    p:username="${jdbc.username}"
    p:password="${jdbc.password}" >
    <property name="maxActive">
        <value>${jdbc.maxActive}</value>
    </property>  
    <property name="initialSize">
        <value>${jdbc.initialSize}</value>
    </property>  
    <property name="maxWait">
        <value>${jdbc.maxWait}</value>
    </property>  
    <property name="maxIdle">
        <value>${jdbc.maxIdle}</value>
    </property>
    <property name="minIdle">
        <value>${jdbc.minIdle}</value>
    </property>
    <!-- 只要下面两个参数设置成小于8小时(MySql默认)，就能避免MySql的8小时自动断开连接问题 -->
    <property name="timeBetweenEvictionRunsMillis">
        <value>18000000</value>
    </property><!-- 5小时 -->
    <property name="minEvictableIdleTimeMillis">
        <value>10800000</value>
    </property><!-- 3小时 -->
    <property name="validationQuery">
        <value>SELECT 1</value>
    </property>
    <property name="testOnBorrow">
        <value>true</value>
    </property>
</bean>

<!-- define the SqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="defaultDataSource" />
    <property name="typeAliasesPackage" value="demo.salesorder,demo.person" />
    <!-- 可以单独指定mybatis的配置文件，或者写在本文件里面。 用下面的自动扫描装配(推荐)或者单独mapper --> 
    <property name="configLocation" value="classpath:sysconfig/mybatis-config.xml" />
</bean>


<!-- 自动扫描并组装MyBatis的映射文件和接口-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="demo.*.data" />
    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
</bean>

<!-- JDBC END -->

<!-- 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">
    <property name="hostName" value="${redis.host}" />
    <property name="port" value="${redis.port}" />
    <property name="password" value="${redis.pass}" />
    <property name="timeout" value="${redis.timeout}" />
    <property name="poolConfig" ref="poolConfig" />
</bean>      
<!-- 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="demo.redis.RedisCacheTransfer">
    <property name="jedisConnectionFactory" ref="jedisConnectionFactory"/>
</bean>      

<bean class="demo.util.UTF8StringBeanPostProcessor"></bean>          
</beans>    

2. mybatis.xml 配置开启二级缓存

    <?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> 
    <!-- 配置mybatis的缓存，延迟加载等等一系列属性 -->
      <settings>
    <!-- 全局映射器启用缓存 *主要将此属性设置完成即可-->
    <setting name="cacheEnabled" value="true"/>
   
    <!-- 查询时，关闭关联对象即时加载以提高性能 -->
    <setting name="lazyLoadingEnabled" value="false"/>
   
    <!-- 对于未知的SQL查询，允许返回不同的结果集以达到通用的效果 -->
    <setting name="multipleResultSetsEnabled" value="true"/>
   
    <!-- 设置关联对象加载的形态，此处为按需加载字段(加载字段由SQL指 定)，不会加载关联表的所有字段，以提高性能 -->
    <setting name="aggressiveLazyLoading" value="true"/>
   
   </settings>
   </configuration>
   

3. 在mapper.xml中映射缓存类RedisCacheClass

     <?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="demo.person.data.UserMapper">
    <cache type="demo.redis.cache.RedisCache"/> <!-- *映射语句 -->
   
    <select id="getPersonList" parameterType="map" resultType="Person">
        select *    
         from person
        <where>
            1=1
            <if test="user_name!=null">
                and user_name=#{user_name}
            </if>    
        </where>
    </select>
    <insert id="addPerson" parameterType="Person" keyProperty="id" useGeneratedKeys="true">
        insert into person(
            login_id,
            user_name,
            gender,
            birthday,
            remark
        )values(
            #{login_id},
            #{user_name},
            #{gender},
            #{birthday},
            #{remark}
        )
    </insert>
   
    </mapper>
   

4. 实现Mybatis中的Cache接口

• Cache.class源码：

    /*
     *    Copyright 2009-2012 the original author or authors.
     *    http://www.apache.org/licenses/LICENSE-2.0*/
    package org.apache.ibatis.cache;
  
    import java.util.concurrent.locks.ReadWriteLock;
  
    public interface Cache {
  
      String getId();
  
      int getSize();
  
      void putObject(Object key, Object value);
  
      Object getObject(Object key);
  
      Object removeObject(Object key);
  
      void clear();
  
      ReadWriteLock getReadWriteLock();
  
    }
  

• RedisCache.java

    package demo.redis.cache;
  
    import java.util.concurrent.locks.ReadWriteLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock;
  
    import org.apache.ibatis.cache.Cache;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    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;
  
  
    public class RedisCache implements Cache //实现类
    {
        private static final Logger logger = LoggerFactory.getLogger(RedisCache.class);
  
        private static JedisConnectionFactory jedisConnectionFactory;
  
        private final String id;
  
        /**
         * The {@code ReadWriteLock}.
         */
        private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
  
        public RedisCache(final String id) {
            if (id == null) {
                throw new IllegalArgumentException("Cache instances require an ID");
            }
            logger.debug("MybatisRedisCache:id=" + id);
            this.id = id;
        }
  
        @Override
        public void clear()
        {
            JedisConnection connection = null;
            try
            {
                connection = jedisConnectionFactory.getConnection(); //连接清除数据
                connection.flushDb();
                connection.flushAll();
            }
            catch (JedisConnectionException e)
            {
                e.printStackTrace();
            }
            finally
            {
                if (connection != null) {
                    connection.close();
                }
            }
        }
  
        @Override
        public String getId()
        {
            return this.id;
        }
  
        @Override
        public Object getObject(Object key)
        {
            Object result = null;
            JedisConnection connection = null;
            try
            {
                connection = jedisConnectionFactory.getConnection();
                RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer(); //借用                spring_data_redis.jar中的JdkSerializationRedisSerializer.class
                result = serializer.deserialize(connection.get(serializer.serialize(key))); //利用其反序列化方法获取值
            }
            catch (JedisConnectionException e)
            {
                e.printStackTrace();
            }
            finally
            {
                if (connection != null) {
                    connection.close();
                }
            }
            return result;
        }
  
        @Override
        public ReadWriteLock getReadWriteLock()
        {
            return this.readWriteLock;
        }
  
        @Override
        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;
        }
  
        @Override
        public void putObject(Object key, Object value)
        {
            JedisConnection connection = null;
            try
            {
                logger.info(">>>>>>>>>>>>>>>>>>>>>>>>putObject:"+key+"="+value);
                connection = jedisConnectionFactory.getConnection();
                RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer(); //借用        spring_data_redis.jar中的JdkSerializationRedisSerializer.class
                connection.set(serializer.serialize(key), serializer.serialize(value)); //利用其序列化方法将数据写入redis服务的缓存中
  
            }
            catch (JedisConnectionException e)
            {
                e.printStackTrace();
            }
            finally
            {
                if (connection != null) {
                    connection.close();
                }
            }
        }
  
        @Override
        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;
        }
  
        public static void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {
            RedisCache.jedisConnectionFactory = jedisConnectionFactory;
        }
  
    }