I have a spring boot project and getting some error related to javax servlet filter.

Is it some kind of version compatibility or I am missing something in pom file.

Following is the log from the console and the pom file.

I have been searching all over, couldn't find anything.

Exception in thread "main" java.lang.IllegalStateException: Cannot load configuration class: org.springframework.security.oauth2.config.annotation.web.configuration.AuthorizationServerSecurityConfiguration at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:403) at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanFactory(ConfigurationClassPostProcessor.java:249) at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:281) at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:125) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:687) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:525) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) at com.abc.application.Application.main(Application.java:15) Caused by: java.lang.IllegalStateException: Unable to load cache item at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:79) at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34) at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116) at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291) at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:480) at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:337) at org.springframework.context.annotation.ConfigurationClassEnhancer.createClass(ConfigurationClassEnhancer.java:138) at org.springframework.context.annotation.ConfigurationClassEnhancer.enhance(ConfigurationClassEnhancer.java:110) at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:393) ... 11 more Caused by: java.lang.NoClassDefFoundError: javax/servlet/Filter at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671) at java.lang.Class.getDeclaredConstructors(Class.java:2020) at org.springframework.cglib.proxy.Enhancer.generateClass(Enhancer.java:566) at org.springframework.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33) at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanFactoryAwareGeneratorStrategy.generate(ConfigurationClassEnhancer.java:252) at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329) at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:492) at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93) at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91) at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61) ... 19 more Caused by: java.lang.ClassNotFoundException: javax.servlet.Filter at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ... 33 more 

3 Answers

For me problem were in pom file (in spring boot 2 project), when I used a parent spring boot in version 2.1.9 which under the hood uses spring-core in version 5.1.10.RELEASE

 <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.9.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> 

I had dependency:

 <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>5.2.0.RELEASE</version> </dependency> 

removing it resolved problem

I was getting the similar error in my Gradle project(might be a problem with Maven too) when I was trying to upgrade my Spring Boot version to latest one.

A quick gradle clean solved that problem for me.

Usually, this Filter class can be found in embedded tomcat jar. So please make sure that your application (jar) contains this file:

Open up the Jar file of the compiled spring boot application and check whether the jar named like tomcat-embed-core resides in the BOOT-INF\lib folder.

This answer is valid as long as you're running tomcat of course + use JAR artifact for spring boot application (for WAR the folder is different, probably WEB-INF/lib although I've never worked with WARs of Spring Boot application so I might be wrong here)

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