mybatis使用redis做二级缓存

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1. 介绍

　　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。

　　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。

2. 使用思路

　　2.1 配置redis.xml 设置redis服务连接各参数

　　2.1 在配置文件中使用 <setting> 标签，设置开启二级缓存；

　　2.2 在mapper.xml 中使用<cache type=”com.demo.RedisCacheClass” /> 将cache映射到指定的RedisCacheClass类中；

　　2.3 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；

　　2.4 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；

3. 代码实践

　　3.1 配置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>

　　3.2 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>

　　 3.3 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>

　　3.4 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;    }}

　　4. 总结

　　　　通过重写Cache类中的方法，将mybatis中默认的缓存空间映射到redis空间中。

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