前言

大家在工作中可能会遇到这样的需求，即Redis读写分离，目的是为了压力分散化。下面我将为大家介绍借助AWS的ELB实现读写分离，以写主读从为例。

实现

引用库文件

    <!-- redis客户端 -->
    <dependency>
      <groupId>redis.clients</groupId>
      <artifactId>jedis</artifactId>
      <version>2.6.2</version>
    </dependency>

方式一，借助切面

JedisPoolSelector

此类的目的是为读和写分别配置不同的注解，用来区分是主还是从。

package com.silence.spring.redis.readwriteseparation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Created by keysilence on 16/10/26.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface JedisPoolSelector {

    String value();

}

JedisPoolAspect

此类的目的是针对主和从的注解，进行动态链接池调配，即主的使用主链接池，从的使用从连接池。

package com.silence.spring.redis.readwriteseparation;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import redis.clients.jedis.JedisPool;

import javax.annotation.PostConstruct;
import java.lang.reflect.Method;
import java.util.Date;

/**
 * Created by keysilence on 16/10/26.
 */
@Aspect
public class JedisPoolAspect implements ApplicationContextAware {

    private ApplicationContext ctx;

    @PostConstruct
    public void init() {
        System.out.println("jedis pool aspectj started @" + new Date());
    }

    @Pointcut("execution(* com.silence.spring.redis.readwriteseparation.util.*.*(..))")
    private void allMethod() {

    }

    @Before("allMethod()")
    public void before(JoinPoint point)
    {
        Object target = point.getTarget();
        String method = point.getSignature().getName();

        Class classz = target.getClass();

        Class<?>[] parameterTypes = ((MethodSignature) point.getSignature())
                .getMethod().getParameterTypes();
        try {
            Method m = classz.getMethod(method, parameterTypes);
            if (m != null && m.isAnnotationPresent(JedisPoolSelector.class)) {
                JedisPoolSelector data = m
                        .getAnnotation(JedisPoolSelector.class);
                JedisPool jedisPool = (JedisPool) ctx.getBean(data.value());
                DynamicJedisPoolHolder.putJedisPool(jedisPool);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.ctx = applicationContext;
    }

}

DynamicJedisPoolHolder

此类目的是存储当前使用的JedisPool，即上面类赋值后的结果保存。

package com.silence.spring.redis.readwriteseparation;

import redis.clients.jedis.JedisPool;

/**
 * Created by keysilence on 16/10/26.
 */
public class DynamicJedisPoolHolder {

    public static final ThreadLocal<JedisPool> holder = new ThreadLocal<JedisPool>();

    public static void putJedisPool(JedisPool jedisPool) {
        holder.set(jedisPool);
    }

    public static JedisPool getJedisPool() {
        return holder.get();
    }

}

RedisUtils

此类目的是对Redis具体的调用，里面包含使用主还是从的方式调用。

package com.silence.spring.redis.readwriteseparation.util;

import com.silence.spring.redis.readwriteseparation.DynamicJedisPoolHolder;
import com.silence.spring.redis.readwriteseparation.JedisPoolSelector;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Created by keysilence on 16/10/26.
 */
public class RedisUtils {
    private static Logger logger = LoggerFactory.getLogger(RedisUtils.class);

    @JedisPoolSelector("master")
    public String setString(final String key, final String value) {

        String ret = DynamicJedisPoolHolder.getJedisPool().getResource().set(key, value);
        System.out.println("key:" + key + ",value:" + value + ",ret:" + ret);

        return ret;
    }

    @JedisPoolSelector("slave")
    public String get(final String key) {

        String ret = DynamicJedisPoolHolder.getJedisPool().getResource().get(key);
        System.out.println("key:" + key + ",ret:" + ret);

        return ret;
    }

}

spring-datasource.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:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <bean id="poolConfig" class="redis.clients.jedis.JedisPoolConfig">
        <!-- 池中最大链接数 -->
        <property name="maxTotal" value="100"/>
        <!-- 池中最大空闲链接数 -->
        <property name="maxIdle" value="50"/>
        <!-- 池中最小空闲链接数 -->
        <property name="minIdle" value="20"/>
        <!-- 当池中链接耗尽，调用者最大阻塞时间，超出此时间将跑出异常。（单位：毫秒；默认为-1，表示永不超时） -->
        <property name="maxWaitMillis" value="1000"/>
        <!-- 参考：http://biasedbit.com/redis-jedispool-configuration/ -->
        <!-- 调用者获取链接时，是否检测当前链接有效性。无效则从链接池中移除，并尝试继续获取。（默认为false） -->
        <property name="testOnBorrow" value="true" />
        <!-- 向链接池中归还链接时，是否检测链接有效性。（默认为false） -->
        <property name="testOnReturn" value="true" />
        <!-- 调用者获取链接时，是否检测空闲超时。如果超时，则会被移除（默认为false） -->
        <property name="testWhileIdle" value="true" />
        <!-- 空闲链接检测线程一次运行检测多少条链接 -->
        <property name="numTestsPerEvictionRun" value="10" />
        <!-- 空闲链接检测线程检测周期。如果为负值，表示不运行检测线程。（单位：毫秒，默认为-1） -->
        <property name="timeBetweenEvictionRunsMillis" value="60000" />
        <!-- 链接获取方式。队列：false；栈：true -->
        <!--<property name="lifo" value="false" />-->
    </bean>

    <bean id="master" class="redis.clients.jedis.JedisPool">
        <constructor-arg index="0" ref="poolConfig"/>
        <constructor-arg index="1" value="192.168.100.110" type="java.lang.String"/>
        <constructor-arg index="2" value="6379" type="int"/>
    </bean>

    <bean id="slave" class="redis.clients.jedis.JedisPool">
        <constructor-arg index="0" ref="poolConfig"/>
        <!-- 此处Host配置成ELB地址 -->
        <constructor-arg index="1" value="192.168.100.110" type="java.lang.String"/>
        <constructor-arg index="2" value="6380" type="int"/>
    </bean>

    <bean id="redisUtils" class="com.silence.spring.redis.readwriteseparation.util.RedisUtils">
    </bean>

    <bean id="jedisPoolAspect" class="com.silence.spring.redis.readwriteseparation.JedisPoolAspect" />

    <aop:aspectj-autoproxy proxy-target-class="true"/>

</beans>

Test

package com.silence.spring.redis.readwriteseparation;

import com.silence.spring.redis.readwriteseparation.util.RedisUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by keysilence on 16/10/26.
 */
public class Test {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("spring-datasource.xml");

        System.out.println(ctx);

        RedisUtils redisUtils = (RedisUtils) ctx.getBean("redisUtils");
        redisUtils.setString("aaa", "111");

        System.out.println(redisUtils.get("aaa"));
    }

}

方式二，依赖注入

与方式一类似，但是需要写死具体使用主的池还是从的池，思路如下：
放弃注解的方式，直接将主和从的两个链接池注入到具体实现类中。

RedisUtils

package com.silence.spring.redis.readwriteseparation.util;

import com.silence.spring.redis.readwriteseparation.DynamicJedisPoolHolder;
import com.silence.spring.redis.readwriteseparation.JedisPoolSelector;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import redis.clients.jedis.JedisPool;

/**
 * Created by keysilence on 16/10/26.
 */
public class RedisUtils {
    private static Logger logger = LoggerFactory.getLogger(RedisUtils.class);

    private JedisPool masterJedisPool;

    private JedisPool slaveJedisPool;

    public void setMasterJedisPool(JedisPool masterJedisPool) {
        this.masterJedisPool = masterJedisPool;
    }

    public void setSlaveJedisPool(JedisPool slaveJedisPool) {
        this.slaveJedisPool = slaveJedisPool;
    }

    public String setString(final String key, final String value) {

        String ret = masterJedisPool.getResource().set(key, value);
        System.out.println("key:" + key + ",value:" + value + ",ret:" + ret);

        return ret;
    }

    public String get(final String key) {

        String ret = slaveJedisPool.getResource().get(key);
        System.out.println("key:" + key + ",ret:" + ret);

        return ret;
    }

}

spring-datasource.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:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <bean id="poolConfig" class="redis.clients.jedis.JedisPoolConfig">
        <!-- 池中最大链接数 -->
        <property name="maxTotal" value="100"/>
        <!-- 池中最大空闲链接数 -->
        <property name="maxIdle" value="50"/>
        <!-- 池中最小空闲链接数 -->
        <property name="minIdle" value="20"/>
        <!-- 当池中链接耗尽，调用者最大阻塞时间，超出此时间将跑出异常。（单位：毫秒；默认为-1，表示永不超时） -->
        <property name="maxWaitMillis" value="1000"/>
        <!-- 参考：http://biasedbit.com/redis-jedispool-configuration/ -->
        <!-- 调用者获取链接时，是否检测当前链接有效性。无效则从链接池中移除，并尝试继续获取。（默认为false） -->
        <property name="testOnBorrow" value="true" />
        <!-- 向链接池中归还链接时，是否检测链接有效性。（默认为false） -->
        <property name="testOnReturn" value="true" />
        <!-- 调用者获取链接时，是否检测空闲超时。如果超时，则会被移除（默认为false） -->
        <property name="testWhileIdle" value="true" />
        <!-- 空闲链接检测线程一次运行检测多少条链接 -->
        <property name="numTestsPerEvictionRun" value="10" />
        <!-- 空闲链接检测线程检测周期。如果为负值，表示不运行检测线程。（单位：毫秒，默认为-1） -->
        <property name="timeBetweenEvictionRunsMillis" value="60000" />
        <!-- 链接获取方式。队列：false；栈：true -->
        <!--<property name="lifo" value="false" />-->
    </bean>

    <bean id="masterJedisPool" class="redis.clients.jedis.JedisPool">
        <constructor-arg index="0" ref="poolConfig"/>
        <constructor-arg index="1" value="192.168.100.110" type="java.lang.String"/>
        <constructor-arg index="2" value="6379" type="int"/>
    </bean>

    <bean id="slaveJedisPool" class="redis.clients.jedis.JedisPool">
        <constructor-arg index="0" ref="poolConfig"/>
        <constructor-arg index="1" value="192.168.100.110" type="java.lang.String"/>
        <constructor-arg index="2" value="6380" type="int"/>
    </bean>

    <bean id="redisUtils" class="com.silence.spring.redis.readwriteseparation.util.RedisUtils">
        <property name="masterJedisPool" ref="masterJedisPool"/>
        <property name="slaveJedisPool" ref="slaveJedisPool"/>
    </bean>

</beans>