概述
缓存框架我们有ehcache 和 redis 分别是 本地内存缓存和 分布式缓存框架。在实际情况下如果单台机器 使用ehcache 就可以满足需求了，速度快效率高，有些数据如果需要多台机器共享这个时候怎么办呢，我们需要通过redis，将缓存存放到redis上面。
这也会导致一个问题，因为所有的请求都会到redis读取，当大量的读取会导致大量的网络流量，因此网络流量会成为访问的瓶颈。
J2CACHE就是解决这个问题而生的，缓存分为两级
L1： 进程内缓存(caffeine\ehcache)
L2： Redis/Memcached 集中式缓存
数据读取流程
读取顺序 -> L1 -> L2
缓存先读取L1 ,不存在则读取L2
数据更新
1 从数据库中读取最新数据，依次更新 L1 -> L2 ，发送广播清除某个缓存信息
2 接收到广播（手工清除缓存 & 一级缓存自动失效），从 L1 中清除指定的缓存信息
测试J2CACHE
创建一个maven 项目
引入
<dependency><!-- Ehcache 3.x //-->
<groupId>org.ehcache</groupId>
<artifactId>ehcache</artifactId>
<version>3.4.0</version>
</dependency> <dependency>
<groupId>net.oschina.j2cache</groupId>
<artifactId>j2cache-core</artifactId>
<version>2.7.7-release</version>
</dependency>
引入配置文件
ehcache3.xml
j2cache.properties
这个配置文件配置如下：
#J2Cache configuration#########################################
# Cache Broadcast Method
# values:
# jgroups -> use jgroups's multicast
# redis -> use redis publish/subscribe mechanism (using jedis)
# lettuce -> use redis publish/subscribe mechanism (using lettuce, Recommend)
# rabbitmq -> use RabbitMQ publisher/consumer mechanism
# rocketmq -> use RocketMQ publisher/consumer mechanism
# none -> don't notify the other nodes in cluster
# xx.xxxx.xxxx.Xxxxx your own cache broadcast policy classname that implement net.oschina.j2cache.cluster.ClusterPolicy
#########################################j2cache.broadcast = redis#########################################
# Level 1&2 provider
# values:
# none -> disable this level cache
# ehcache -> use ehcache2 as level 1 cache
# ehcache3 -> use ehcache3 as level 1 cache
# caffeine -> use caffeine as level 1 cache(only in memory)
# redis -> use redis as level 2 cache (using jedis)
# lettuce -> use redis as level 2 cache (using lettuce)
# readonly-redis -> use redis as level 2 cache ,but never write data to it. if use this provider, you must uncomment `j2cache.L2.config_section` to make the redis configurations available.
# memcached -> use memcached as level 2 cache (xmemcached),
# [classname] -> use custom provider
#########################################j2cache.L1.provider_class = ehcache3
j2cache.L2.provider_class = redis# When L2 provider isn't `redis`, using `L2.config_section = redis` to read redis configurations
# j2cache.L2.config_section = redis# Enable/Disable ttl in redis cache data (if disabled, the object in redis will never expire, default:true)
# NOTICE: redis hash mode (redis.storage = hash) do not support this feature)
j2cache.sync_ttl_to_redis = true# Whether to cache null objects by default (default false)
j2cache.default_cache_null_object = true#########################################
# Cache Serialization Provider
# values:
# fst -> using fast-serialization (recommend)
# kyro -> using kyro serialization
# json -> using fst's json serialization (testing)
# fastjson -> using fastjson serialization (embed non-static class not support)
# java -> java standard
# [classname implements Serializer]
#########################################j2cache.serialization = fst
#json.map.person = net.oschina.j2cache.demo.Person#########################################
# Ehcache configuration
########################################## ehcache.configXml = /ehcache.xml# ehcache3.configXml = /ehcache3.xml
# ehcache3.defaultHeapSize = 1000#########################################
# Redis connection configuration
##################################################################################
# Redis Cluster Mode
#
# single -> single redis server
# sentinel -> master-slaves servers
# cluster -> cluster servers (\u93c1\u7248\u5d41\u6434\u64bb\u53a4\u7f03\ue1bd\u68e4\u93c1\u582c\u7d1d\u6d63\u8de8\u6564 database = 0\u951b\ufffd
# sharded -> sharded servers (\u7035\u55d9\u721c\u9286\u4f79\u669f\u93b9\ue1bc\u7c31\u8e47\u5474\u300f\u9366\ufffd hosts \u6d93\ue15f\u5bda\u7039\u6c3e\u7d1d\u6d93\u65c7\u7e5b\u93ba\u30e6\u775c\u95b0\u5d87\u7586\u93c3\u72b3\u6665 ; redis://user:password@127.0.0.1:6379/0\u951b\ufffd
#
#########################################redis.mode = sentinel#redis storage mode (generic|hash)
redis.storage = generic## redis pub/sub channel name
redis.channel = j2cache
## redis pub/sub server (using redis.hosts when empty)
redis.channel.host =#cluster name just for sharded
redis.cluster_name = mymaster## redis cache namespace optional, default[empty]
redis.namespace =## connection
# Separate multiple redis nodes with commas, such as 192.168.0.10:6379,192.168.0.11:6379,192.168.0.12:6379redis.hosts = 202.10.79.170:16001,202.10.79.170:16002,202.10.79.170:16003
redis.timeout = 10000
redis.password =
redis.database = 0## redis pool properties
redis.maxTotal = 100
redis.maxIdle = 10
redis.maxWaitMillis = 5000
redis.minEvictableIdleTimeMillis = 60000
redis.minIdle = 1
redis.numTestsPerEvictionRun = 10
redis.lifo = false
redis.softMinEvictableIdleTimeMillis = 10
redis.testOnBorrow = true
redis.testOnReturn = false
redis.testWhileIdle = true
redis.timeBetweenEvictionRunsMillis = 300000
redis.blockWhenExhausted = false
redis.jmxEnabled = false
广播方式使用redis
j2cache.broadcast = redis
L1,L2 缓存实现方法
j2cache.L1.provider_class = ehcache3
j2cache.L2.provider_class = redis
redis 使用哨兵模式进行配置。
使用代码进行测试
编写测试代码如下：
读取缓存
public static void main(String[] args) throws InterruptedException { CacheChannel cache = J2Cache.getChannel();
while(true){
System.out.println(cache.get("user", "name"));
Thread.sleep(2000);
}
}
这个代码会一直读取 user:name 的缓存。
我们需要测试的是，当一个客户端设置一个 user:name 的缓存时，这个代码能反映缓存的变化。
设置缓存：
public static void main(String[] args) { CacheChannel cache = J2Cache.getChannel();
cache.set("user", "name", "A");
cache.close();
}
首先设置一个A的缓存。
我们可以看到第一个代码返回的是如下情况
[user,name,L2]=>A
[user,name,L1]=>A
[user,name,L1]=>A
它会先从 redis读取，在读取本地。
我们在设置一次：
public static void main(String[] args) { CacheChannel cache = J2Cache.getChannel();
cache.set("user", "name", "B");
cache.close();
}
第二次我们这个name 为 B，这个时候我们可以发现：
[user,name,L2]=>B
[user,name,L1]=>B
[user,name,L1]=>B
缓存变成了B ，而且是先读取 REDIS ，在读取 EHCACHE缓存，即先读取 L2 再读取L1。
这样我们的缓存就既能保证性能，有可以保证缓存及时被更新。
