SpringBoot 项目启动时解决报错：Unable to connect to Redis； nested exception is io.lettuce.core.RedisConnection

报错信息如下：

2021-10-24 23:11:33.297 ERROR 5952 --- [           main] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Failed to execute CommandLineRunner
	at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:794)
	at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:775)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:345)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1332)
	at com.youlai.admin.AdminApplication.main(AdminApplication.java:11)
Caused by: org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis; nested exception is io.lettuce.core.RedisConnectionException: Unable to connect to localhost:6379
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$ExceptionTranslatingConnectionProvider.translateException(LettuceConnectionFactory.java:1671)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$ExceptionTranslatingConnectionProvider.getConnection(LettuceConnectionFactory.java:1579)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getNativeConnection(LettuceConnectionFactory.java:1365)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getConnection(LettuceConnectionFactory.java:1348)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getSharedConnection(LettuceConnectionFactory.java:1089)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getConnection(LettuceConnectionFactory.java:421)
	at org.springframework.data.redis.core.RedisConnectionUtils.fetchConnection(RedisConnectionUtils.java:193)
	at org.springframework.data.redis.core.RedisConnectionUtils.doGetConnection(RedisConnectionUtils.java:144)
	at org.springframework.data.redis.core.RedisConnectionUtils.getConnection(RedisConnectionUtils.java:105)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:209)
	at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:189)
	at org.springframework.data.redis.core.RedisTemplate.delete(RedisTemplate.java:726)
	at com.youlai.admin.service.impl.SysPermissionServiceImpl.refreshPermRolesRules(SysPermissionServiceImpl.java:39)
	at com.youlai.admin.service.impl.SysPermissionServiceImpl$$FastClassBySpringCGLIB$$392a65e3.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
	at com.youlai.admin.service.impl.SysPermissionServiceImpl$$EnhancerBySpringCGLIB$$1b054601.refreshPermRolesRules(<generated>)
	at com.youlai.admin.component.InitPermissionRolesCache.run(InitPermissionRolesCache.java:19)
	at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:791)
	... 5 common frames omitted
Caused by: io.lettuce.core.RedisConnectionException: Unable to connect to localhost: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:330)
	at io.lettuce.core.RedisClient.connect(RedisClient.java:216)
	at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.lambda$getConnection$1(StandaloneConnectionProvider.java:115)
	at java.util.Optional.orElseGet(Optional.java:267)
	at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.getConnection(StandaloneConnectionProvider.java:115)
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$ExceptionTranslatingConnectionProvider.getConnection(LettuceConnectionFactory.java:1577)
	... 22 common frames omitted
Caused by: io.lettuce.core.RedisCommandExecutionException: ERR Client sent AUTH, but no password is set

解决方案：

配置文件中 password 行不要注释，如果连接 redis 不需要密码，则设置值为空即可。