分布式缓存技术redis学习系列（九）

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>
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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();

}
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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;
  }

}
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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();
  }

}
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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;
  }

}
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spring-datasource.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www./schema/beans"
    xmlns:xsi="http://www./2001/XMLSchema-instance" xmlns:aop="http://www./schema/aop"
    xsi:schemaLocation="http://www./schema/beans http://www./schema/beans/spring-beans.xsd http://www./schema/aop http://www./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:///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>
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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"));
  }

}
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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;
  }

}
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spring-datasource.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www./schema/beans"
    xmlns:xsi="http://www./2001/XMLSchema-instance" xmlns:aop="http://www./schema/aop"
    xsi:schemaLocation="http://www./schema/beans http://www./schema/beans/spring-beans.xsd http://www./schema/aop http://www./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:///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>
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转载：http://www.jb51.net/article/95997.htm