学习过程中遇到了如下问题：
Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/Filter at java.base/java.lang.ClassLoader.defineClass1(Native Method) at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012) at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150) at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862) at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) at java.base/java.lang.ClassLoader.defineClass1(Native Method) at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012) at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150) at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862) at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) at java.base/java.lang.ClassLoader.defineClass1(Native Method) at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012) at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150) at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862) at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) at java.base/java.lang.ClassLoader.defineClass1(Native Method) at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012) at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150) at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862) at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681) at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:467) at java.base/sun.reflect.generics.factory.CoreReflectionFactory.makeNamedType(CoreReflectionFactory.java:114) at java.base/sun.reflect.generics.visitor.Reifier.visitClassTypeSignature(Reifier.java:125) at java.base/sun.reflect.generics.tree.ClassTypeSignature.accept(ClassTypeSignature.java:49) at java.base/sun.reflect.generics.visitor.Reifier.reifyTypeArguments(Reifier.java:68) at java.base/sun.reflect.generics.visitor.Reifier.visitClassTypeSignature(Reifier.java:138) at java.base/sun.reflect.generics.tree.ClassTypeSignature.accept(ClassTypeSignature.java:49) at java.base/sun.reflect.generics.repository.ClassRepository.computeSuperInterfaces(ClassRepository.java:117) at java.base/sun.reflect.generics.repository.ClassRepository.getSuperInterfaces(ClassRepository.java:95) at java.base/java.lang.Class.getGenericInterfaces(Class.java:1211) at org.springframework.core.ResolvableType.getInterfaces(ResolvableType.java:500) at org.springframework.core.ResolvableType.as(ResolvableType.java:448) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$FactoryBeanMethodTypeFinder.doWith(AbstractAutowireCapableBeanFactory.java:1935) at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:366) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryBeanFromMethod(AbstractAutowireCapableBeanFactory.java:935) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryBean(AbstractAutowireCapableBeanFactory.java:874) at org.springframework.beans.factory.support.AbstractBeanFactory.isTypeMatch(AbstractBeanFactory.java:619) at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:572) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:531) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:658) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:650) at org.springframework.context.support.AbstractApplicationContext.getBeansOfType(AbstractApplicationContext.java:1276) at org.springframework.boot.SpringApplication.getExitCodeFromMappedException(SpringApplication.java:863) at org.springframework.boot.SpringApplication.getExitCodeFromException(SpringApplication.java:851) at org.springframework.boot.SpringApplication.handleExitCode(SpringApplication.java:838) at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:778) at org.springframework.boot.SpringApplication.run(SpringApplication.java:321) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291) at com.demo.SpringbootShiroApplication.main(SpringbootShiroApplication.java:10) Caused by: java.lang.ClassNotFoundException: javax.servlet.Filter at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) ... 67 more
有用的方法（在pom.xml中加入以下依赖）：
<dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.1</version> </dependency>
