SpringBoot项目启动会出现以下错误：
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:163) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:577) ~[spring-context-5.3.7.jar:5.3.7] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) [spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:438) [spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.SpringApplication.run(SpringApplication.java:337) [spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1336) [spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1325) [spring-boot-2.5.0.jar:2.5.0] at com.wfy.example.server.SmartOfficeApplication.main(SmartOfficeApplication.java:12) [classes/:na] Caused by: org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:142) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:104) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:450) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:199) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:182) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:160) ~[spring-boot-2.5.0.jar:2.5.0] ... 8 common frames omitted Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'securityConfig': Unsatisfied dependency expressed through field 'adminService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'adminServiceImpl': Unsatisfied dependency expressed through field 'baseMapper'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'adminMapper' defined in file [G:\IDEAProgram\SmartOfficeProject\smart_office\smart_server\target\classes\com\wfy\example\server\mapper\AdminMapper.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [com/baomidou/mybatisplus/autoconfigure/MybatisPlusAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [G:\IDEAProgram\SmartOfficeProject\smart_office\smart_server\target\classes\mapper\AdminRoleMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [G:\IDEAProgram\SmartOfficeProject\smart_office\smart_server\target\classes\mapper\AdminRoleMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'com.wfy.example.pojo.AdminRole'. Cause: java.lang.ClassNotFoundException: Cannot find class: com.wfy.example.pojo.AdminRole at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:660) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1413) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:601) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:524) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:410) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1334) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:564) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:524) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:213) ~[spring-beans-5.3.7.jar:5.3.7] at org.springframework.boot.web.servlet.ServletContextInitializerBeans.getOrderedBeansOfType(ServletContextInitializerBeans.java:212) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:175) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:170) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAdaptableBeans(ServletContextInitializerBeans.java:155) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.ServletContextInitializerBeans.<init>(ServletContextInitializerBeans.java:87) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getServletContextInitializerBeans(ServletWebServerApplicationContext.java:260) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.selfInitialize(ServletWebServerApplicationContext.java:234) ~[spring-boot-2.5.0.jar:2.5.0] at org.springframework.boot.web.embedded.tomcat.TomcatStarter.onStartup(TomcatStarter.java:53) ~[spring-boot-2.5.0.jar:2.5.0] at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5161) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_144] at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_144] at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:829) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_144] at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134) ~[na:1.8.0_144] at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.StandardService.startInternal(StandardService.java:433) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.apache.catalina.startup.Tomcat.start(Tomcat.java:486) ~[tomcat-embed-core-9.0.46.jar:9.0.46] at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:123) ~[spring-boot-2.5.0.jar:2.5.0] ... 13 common frames omitted，，，，
1、经过认真的筛查，发现是Mapper.xml文件中namespace的路径不对，其标使用Ctrl+鼠标发到namespace中，如果该路径有下划线，说明路径是对的，我的放鼠标上去没有下划线。
2、这种弹出大量的错误信息，一般都是从后面哪些Caused by:找问题，像Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML.就是mapperXML中有问题，ibatis就是数据库xml的定位出现了问题。