16-1 Redis分布式缓存引入与保存缓存功能实现

r囧r小猫 2021-11-05 19:26 200阅读 0赞

现在功能已经完成了，但是我们还是要考虑一下性能问题，现在任何请求都是要到数据库中查询很多的数据，才能知道当前的用户是否有权限可以访问当前的url，当我们的请求量很大时，它对我们数据库的请求量也是非常大的，这时，我们就会想到对我们的权限进行缓存，

这里就讲一下权限的缓存如何进行，

这里使用的是redis

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<?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"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    
    
    
        <context:property-placeholder location="classpath:redis.properties" />
    
    
        <bean id="jedisPoolConfig" class="redis.clients.jedis.JedisPoolConfig" />
    
    
        <bean id="shardedJedisPool" class="redis.clients.jedis.ShardedJedisPool" scope="singleton" >
    
            <constructor-arg index="0" ref="jedisPoolConfig" />
            <constructor-arg index="1">
                <list>
    
                    <bean class="redis.clients.jedis.JedisShardInfo">
                        <constructor-arg name="host" value="${redis.host}"/>
                        <constructor-arg name="port" value="${redis.port}"/>
                        <constructor-arg name="timeout" value="${redis.timeout}"/>
                    </bean>
                </list>
            </constructor-arg>
        </bean>
    
    </beans>

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redis.host=127.0.0.1
    redis.port=6379
    redis.timeout=3000

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package com.mmall.service;
    
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.stereotype.Service;
    import redis.clients.jedis.ShardedJedis;
    import redis.clients.jedis.ShardedJedisPool;
    
    import javax.annotation.Resource;
    
    
    
    //  封装一下radis
    @Service("redisPool")//加注释让spring来管理
    @Slf4j
    public class RedisPool {
    
    //    使用刚刚定义的spring管理的类radis
        @Resource(name = "shardedJedisPool")//直接调用radis了  单例的serviece
        private ShardedJedisPool shardedJedisPool;
    
        //返回单例的实例
        public ShardedJedis instance() {
            return shardedJedisPool.getResource();
        }
    
        //安全关闭的方法
        public void safeClose(ShardedJedis shardedJedis) {
            try {
               if (shardedJedis != null) {
                   shardedJedis.close();
               }
            } catch (Exception e) {
                log.error("return redis resource exception", e);
            }
        }
    }

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package com.mmall.service;
    
    import com.google.common.base.Joiner;
    import com.mmall.beans.CacheKeyConstants;
    import com.mmall.util.JsonMapper;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.stereotype.Service;
    import redis.clients.jedis.ShardedJedis;
    
    import javax.annotation.Resource;
    
    @Service
    @Slf4j
    public class SysCacheService {
    
        //引用刚定义的reaispool
        @Resource(name = "redisPool")
        private RedisPool redisPool;
    
        /**
         *
         * @param toSavedValue   要保存的值
         * @param timeoutSeconds   要保存多少秒
         * @param prefix   前缀 自定义
         */
        public void saveCache(String toSavedValue, int timeoutSeconds, CacheKeyConstants prefix) {
            //调用下面的方法
            saveCache(toSavedValue, timeoutSeconds, prefix, null);
        }
    
        //保存cache
        public void saveCache(String toSavedValue, int timeoutSeconds, CacheKeyConstants prefix, String... keys) {
            if (toSavedValue == null) {
                return;
            }
            ShardedJedis shardedJedis = null;
            //网络连接可能会有问题 try catch
            try {
                //1.生成对应的key
                String cacheKey = generateCacheKey(prefix, keys);//拼接key  系统所有权限大家一样  但是单个用户权限大家不一样
                //2.拿到资源
                shardedJedis = redisPool.instance();//单例获取redis
                //提供好的方法处理  一定要写radis 的api
                shardedJedis.setex(cacheKey, timeoutSeconds, toSavedValue);
            } catch (Exception e) {
                log.error("save cache exception, prefix:{}, keys:{}", prefix.name(), JsonMapper.obj2String(keys), e);
            } finally {
                //别忘了释放radis
                redisPool.safeClose(shardedJedis);
            }
        }
    
        //获取cache
        //  参数  前缀    key
        public String getFromCache(CacheKeyConstants prefix, String... keys) {
            ShardedJedis shardedJedis = null;
            String cacheKey = generateCacheKey(prefix, keys);//拼接key  系统所有权限大家一样  但是单个用户权限大家不一样
            try {
                shardedJedis = redisPool.instance();//单例获取redis
                String value = shardedJedis.get(cacheKey);//获取值
                return value;//返回值
            } catch (Exception e) {
                log.error("get from cache exception, prefix:{}, keys:{}", prefix.name(), JsonMapper.obj2String(keys), e);
                return null;
            } finally {
                //别忘了释放radis
                redisPool.safeClose(shardedJedis);
            }
        }
    
        private String generateCacheKey(CacheKeyConstants prefix, String... keys) {
            String key = prefix.name();
            //多个string可以进行拼接
            if (keys != null && keys.length > 0) {
                key += "_" + Joiner.on("_").join(keys);
            }
            return key;
        }
    }

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package com.mmall.beans;
    
    import lombok.Getter;
    
    @Getter
    public enum CacheKeyConstants {
    
        SYSTEM_ACLS,//缓存系统内的所有权限
    
        USER_ACLS;//缓存用户的权限
    
    }

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//从缓存中获取数据
        public List<SysAcl> getCurrentUserAclListFromCache() {
            //userId
            int userId = RequestHolder.getCurrentUser().getId();
            //通过key获取value
            String cacheValue = sysCacheService.getFromCache(CacheKeyConstants.USER_ACLS, String.valueOf(userId));
            if (StringUtils.isBlank(cacheValue)) {
                //为空说明出问题了  重新获取一次
                List<SysAcl> aclList = getCurrentUserAclList();
                if (CollectionUtils.isNotEmpty(aclList)) {
                    //重新保存   value    600s有效期       key的值（前缀和userid）
                    sysCacheService.saveCache(JsonMapper.obj2String(aclList), 600, CacheKeyConstants.USER_ACLS, String.valueOf(userId));
                }
                return aclList;//没从cache中获取到值从数据库取出来
            }
            //缓存中有
            return JsonMapper.string2Obj(cacheValue, new TypeReference<List<SysAcl>>() {
            });
        }
    }

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不是每个方法都要缓存的

有些必须是实时数据不就不能进行缓存

不需要进行特别多的数据访问  就不要缓存

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