连接redis遇到Unable to connect to Redis； nested exception is io.lettuce.core.RedisConnectionException：

先来看看异常信息：

org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis; nested exception is io.lettuce.core.RedisConnectionException: Unable to connect to 192.168.232.151:6379
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getNativeConnection(LettuceConnectionFactory.java:1106)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getConnection(LettuceConnectionFactory.java:1085)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getSharedConnection(LettuceConnectionFactory.java:866)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getConnection(LettuceConnectionFactory.java:341)
	at org.springframework.data.redis.core.RedisConnectionUtils.doGetConnection(RedisConnectionUtils.java:132)
	at org.springframework.data.redis.core.RedisConnectionUtils.getConnection(RedisConnectionUtils.java:95)
	at org.springframework.data.redis.core.RedisConnectionUtils.getConnection(RedisConnectionUtils.java:82)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:211)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
	at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:95)
	at org.springframework.data.redis.core.DefaultValueOperations.set(DefaultValueOperations.java:236)
	at com.tianfei.crowd.controller.RedisController.setRedisKeyValueRemote(RedisController.java:30)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	。。。。。。中间省略
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
Caused by: io.lettuce.core.RedisConnectionException: Unable to connect to 192.168.232.151:6379
	at io.lettuce.core.RedisConnectionException.create(RedisConnectionException.java:78)
	at io.lettuce.core.RedisConnectionException.create(RedisConnectionException.java:56)
	at io.lettuce.core.AbstractRedisClient.getConnection(AbstractRedisClient.java:235)
	at io.lettuce.core.RedisClient.connect(RedisClient.java:204)
	at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.lambda$getConnection$1(StandaloneConnectionProvider.java:113)
	at java.util.Optional.orElseGet(Optional.java:267)
	at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.getConnection(StandaloneConnectionProvider.java:113)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getNativeConnection(LettuceConnectionFactory.java:1104)
	... 65 more
Caused by: io.netty.channel.ConnectTimeoutException: connection timed out: /192.168.232.151:6379
	at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe$1.run(AbstractNioChannel.java:267)
	at io.netty.util.concurrent.PromiseTask$RunnableAdapter.call(PromiseTask.java:38)
	at io.netty.util.concurrent.ScheduledFutureTask.run(ScheduledFutureTask.java:127)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:405)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:906)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	... 1 more

连接不到Redis的原因
Caused by: io.netty.channel.ConnectTimeoutException: connection timed out: /192.168.232.151:6379

分析：

• 连接不上Redis的很大一部分原因是：防火墙未关闭，导致请求无法到达 Redis 客户端。

解决办法

• 注意！！！！：CentOS 6 与 CentOS7 的命令可能不太一样，我这里使用的是 Centos6。

• 用 XShell 连接 Linux，切换到 “~”目录查看防火墙状态：

service  iptables  status

• 关闭防火墙：

service  iptables  stop

• 再次查看防火墙，确认已经关闭：
  
• 刷新页面，再次发送请求，请求通过，问题迎刃而解。
  
• 查看redis数据库 是否成功存入
  
  发现 key 为 aaa 的键值对成功存入，问题解决！