报错信息如下：
2022-04-21 17:43:26.473 ERROR [em-service,,,] 17272 --- [ main] org.springframework.boot.SpringApplication : Application run failed java.lang.IllegalStateException: Error processing condition on org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration.propertySourcesPlaceholderConfigurer at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:64) at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:108) at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForBeanMethod(ConfigurationClassBeanDefinitionReader.java:180) at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass(ConfigurationClassBeanDefinitionReader.java:141) at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClassBeanDefinitionReader.java:117) at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:328) at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:233) at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:271) at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:91) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:694) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:398) at org.springframework.boot.SpringApplication.run(SpringApplication.java:330) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1258) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) at com.ey.fssc.em.EmApplication.main(EmApplication.java:30) Caused by: java.lang.reflect.MalformedParameterizedTypeException: null at sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl.validateConstructorArguments(ParameterizedTypeImpl.java:58) at sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl.(ParameterizedTypeImpl.java:51) at sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl.make(ParameterizedTypeImpl.java:92) at sun.reflect.generics.factory.CoreReflectionFactory.makeParameterizedType(CoreReflectionFactory.java:105) at sun.reflect.generics.visitor.Reifier.visitClassTypeSignature(Reifier.java:140) at sun.reflect.generics.tree.ClassTypeSignature.accept(ClassTypeSignature.java:49) at sun.reflect.generics.repository.MethodRepository.getReturnType(MethodRepository.java:68) at java.lang.reflect.Method.getGenericReturnType(Method.java:255) at org.springframework.core.MethodParameter.getGenericParameterType(MethodParameter.java:419) at org.springframework.core.SerializableTypeWrapper$MethodParameterTypeProvider.getType(SerializableTypeWrapper.java:317) at org.springframework.core.SerializableTypeWrapper.forTypeProvider(SerializableTypeWrapper.java:137) at org.springframework.core.ResolvableType.forType(ResolvableType.java:1384) at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1285) at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1251) at org.springframework.core.ResolvableType.forMethodReturnType(ResolvableType.java:1194) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:779) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:659) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:627) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1489) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1012) at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanTypeForNonAliasDefinition(BeanTypeRegistry.java:180) at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanTypeForNonAliasDefinition(BeanTypeRegistry.java:160) at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanType(BeanTypeRegistry.java:153) at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.updateTypesIfNecessary(BeanTypeRegistry.java:215) at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.getNamesForType(BeanTypeRegistry.java:115) at org.springframework.boot.autoconfigure.condition.OnBeanCondition.collectBeanNamesForType(OnBeanCondition.java:265) at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getBeanNamesForType(OnBeanCondition.java:254) at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchingBeans(OnBeanCondition.java:196) at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:116) at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ... 17 common frames omitted
通过：
at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:64)
以为是PropertyPlaceholderAutoConfiguration类没有自动匹配上，查了一下，不是这个问题。
然后通过：
Caused by: java.lang.reflect.MalformedParameterizedTypeException: null at java.lang.reflect.Method.getGenericReturnType(Method.java:255) at org.springframework.core.MethodParameter.getGenericParameterType(MethodParameter.java:419)
发现可能是类型不匹配的问题，到错误发生的地方断点，调试：
从图中可以看出，redis进行配置的时候，返回的类型是GenericObjectPoolConfig，搜索代码，找到redis配置数据源的地方：
定义返回类型确实是GenericObjectPoolConfig，然而，单击GenericObjectPoolConfig，跳转到：
发现引用的类，竟然GenericObjectPoolConfig后不带泛型，好奇怪！
难道是版本问题？于是，查看项目依赖树，发现果然猜测没错，引入了两个不同版本commons-pool的jar：
查阅代码，在2.8.0版本中，用的是带泛型的GenericObjectPoolConfig
问题找到了，于是在pom依赖里边，排除2.5.0版本的jar包。
重启项目，正常。
总结：
遇到问题要冷静，不能只看到问题表象，必要时断点进行原因跟踪查找。
