遇到个很诡异的问题，困扰了我好几天，项目运行不起来导致我无法开发下去。

问题描述：这是个Spring Boot个人项目，从环境的搭建到开发这一过程还是挺顺利的，其中遇到的问题也都解决了，也做了相应的记录，具体可以翻阅我之前的博客，可能有些问题没有记录下来，望谅解。
突然发现使用springboot内嵌的服务器时，有些麻烦的地方，就是每次更改项目中的java等文件时，都要全量打包，如果要使用增量打包的话，则必须使用第三方的应用服务器（Tomcat服务器）。就在使用外部的tomcat服务器部署的时候，就遇到了jar包冲突或找不到相应的类的异常（如，ELManager）。网上也有很多此类的解决方案，可以参考网上的。接下来我所说的是另一个问题，网上很少有这个答案。
当我用IDEA启动springboot项目时，发现报了以下异常：

2019-01-01 10:42:17.407 INFO 26196 — [ main] com.example.demo.DemoApplication : Starting DemoApplication on guyuanhui with PID 26196 (E:\guyuanhui\NewGraduateProject\xiaoyiduo\test1\target\classes started by guyuanhui in E:\guyuanhui\NewGraduateProject\xiaoyiduo\test1)
2019-01-01 10:42:17.411 INFO 26196 — [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default
2019-01-01 10:42:17.477 INFO 26196 — [ main] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@482cd91f: startup date [Tue Jan 01 10:42:17 CST 2019]; root of context hierarchy
2019-01-01 10:42:18.664 WARN 26196 — [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor’: Invocation of init method failed; nested exception is java.lang.IllegalAccessError: javax/el/Util
2019-01-01 10:42:18.673 INFO 26196 — [ main] ConditionEvaluationReportLoggingListener :

Error starting ApplicationContext. To display the conditions report re-run your application with ‘debug’ enabled.
2019-01-01 10:42:18.684 ERROR 26196 — [ main] o.s.boot.SpringApplication : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor’: Invocation of init method failed; nested exception is java.lang.IllegalAccessError: javax/el/Util
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1710) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:583) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:502) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:312)[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310)[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:205)[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:205)[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:709)[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:534)[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]atorg.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.SpringApplication.refresh(SpringApplication.java:752)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:388)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.SpringApplication.run(SpringApplication.java:327)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.SpringApplication.run(SpringApplication.java:1246)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.SpringApplication.run(SpringApplication.java:1234)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atcom.example.demo.DemoApplication.main(DemoApplication.java:10)[classes/:na]Causedby:java.lang.IllegalAccessError:javax/el/Utilatjavax.el.ELManager.getExpressionFactory(ELManager.java:30)[tomcat-embed-el-8.5.28.jar:2.2.FR]atorg.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.buildExpressionFactory(ResourceBundleMessageInterpolator.java:88)[hibernate-validator-6.0.7.Final.jar:6.0.7.Final]atorg.hibernate.validator.messageinterpolation.ResourceBundleMessageInterpolator.<init>(ResourceBundleMessageInterpolator.java:47)[hibernate-validator-6.0.7.Final.jar:6.0.7.Final]atorg.hibernate.validator.internal.engine.ConfigurationImpl.getDefaultMessageInterpolator(ConfigurationImpl.java:461)[hibernate-validator-6.0.7.Final.jar:6.0.7.Final]atorg.springframework.boot.validation.MessageInterpolatorFactory.getObject(MessageInterpolatorFactory.java:54)[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]atorg.springframework.boot.context.properties.ConfigurationPropertiesJsr303Validator$Delegate.(ConfigurationPropertiesJsr303Validator.java:71) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.context.properties.ConfigurationPropertiesJsr303Validator.(ConfigurationPropertiesJsr303Validator.java:43) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.context.properties.ConfigurationPropertiesJsr303Validator.getIfJsr303Present(ConfigurationPropertiesJsr303Validator.java:64) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.context.properties.ConfigurationPropertiesBinder.(ConfigurationPropertiesBinder.java:69) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.afterPropertiesSet(ConfigurationPropertiesBindingPostProcessor.java:78) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1769) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1706) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
… 16 common frames omitted

令我很诧异的是，我IDEA上的代码都没有改动过，我处理的都是外部tomcat的jar包的问题。为什么在IDEA上会突然跑不起来了呢，之前还是可以正常启动的啊！为了解决这个问题，各种方式都使用过了。暴力法：重装IDEA，更改系统变量中指定新的jdk和IDEA下的maven，重新拉取最新版本的项目，更换内嵌的Tomcat版本，再运行，还是这个异常。

问题排查：尝试在另一台电脑上运行此项目，发现可以正常跑起来！可见项目源代码是没有问题的。回到本机，创建了个springboot的demo，发现还是这个问题。所以十分肯定，问题就出在环境上。

最终解决方案。启动项目，发觉到控制台输出的第一行的jdk路径不对，还是原先的。我明明安装了新的jdk并且在系统变量也配置了啊。后来重新引入新的jdk，最后成功跑起来了。可见，问题就出现在jdk身上。

出错原因：为了解决外部tomcat部署springboot项目的问题，根据网上提供的方案，在替换相关的jar包时，可能不小心将jdk中的jar包替换了。所以导致了该异常。除了这个，我找不到其他的原因了，因为之前都是好好的。

总结：为了解决一个小问题，参考了网上的解决方案而引出了其他难以解决的bug。这时可能会考虑极端的解决方法，而在采用极端的方法时，需要检验每一步是否准确无误了，否则后面就不会再回头考虑刚才的极端方法。然而这恰恰是最好的方案。