1. 复现问题

今天在启动spring boot项目时，出现如下错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'redisConnectionFactory' defined in class path resource [org/springframework/boot/autoconfigure/data/redis/LettuceConnectionConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory]: Factory method 'redisConnectionFactory' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/commons/pool2/impl/GenericObjectPoolConfig
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:658)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:638)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1334)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:564)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:524)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:438)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:337)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1336)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1325)
	at com.superjson.superjsonmanager.SuperJsonManagerApplication.main(SuperJsonManagerApplication.java:51)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory]: Factory method 'redisConnectionFactory' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/commons/pool2/impl/GenericObjectPoolConfig
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653)
	... 19 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/commons/pool2/impl/GenericObjectPoolConfig
	at org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration$LettucePoolingClientConfigurationBuilder.<init>(LettucePoolingClientConfiguration.java:94)
	at org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration.builder(LettucePoolingClientConfiguration.java:51)
	at org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration$PoolBuilderFactory.createBuilder(LettuceConnectionConfiguration.java:172)
	at org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration.createBuilder(LettuceConnectionConfiguration.java:110)
	at org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration.getLettuceClientConfiguration(LettuceConnectionConfiguration.java:95)
	at org.springframework.boot.autoconfigure.data.redis.LettuceConnectionConfiguration.redisConnectionFactory(LettuceConnectionConfiguration.java:77)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	... 20 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.commons.pool2.impl.GenericObjectPoolConfig
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 31 common frames omitted

Disconnected from the target VM, address: '127.0.0.1:62013', transport: 'socket'

Process finished with exit code 1

即Error creating bean with name 'redisConnectionFactory' defined in class path resource这个问题，即无法创建redis连接池。

2. 分析问题

导致上述的错误，是不是我的redis配置有问题，还是没有引入redis依赖包呢，于是做如下分析。

查看redis配置

spring:
  # 需要将其设置为always，彩色打印日志
  output:
    ansi:
      enabled: always
  redis:
    database: 0
    host: 127.0.0.1
    lettuce:
      pool:
        max-active: 8
        max-idle: 10
        max-wait: 1ms
        min-idle: 5
      shutdown-timeout: 100ms
    port: 6379

配置没有问题。

查看redis依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

依然没有问题。

继续分析错误日志，看到最后发现报了这个错误，如下图所示：

即java.lang.ClassNotFoundException: org.apache.commons.pool2.impl.GenericObjectPoolConfig，找不到GenericObjectPoolConfig这个类，原因只有没配置这个类的依赖。

3. 解决问题

既然没有引入redis的相关依赖，那就引入如下依赖即可：

<!-- properties中增加redisCommonsPool.version，便于dependncy调用 -->
<properties>
    <java.version>1.8</java.version>
  <redisCommonsPool.version>2.11.1</redisCommonsPool.version>
</properties>

<!-- 引入redis连接池的依赖 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-pool2</artifactId>
    <version>${redisCommonsPool.version}</version>
</dependency>