java.lang.ClassNotFoundException: javax.servlet.Filter:有两个原因：（1）在maven中的作用域，不能是provided，需要是compile就是默认的scope（2）spring-boot-starter-tomcat的版本bug，换个新的或旧的版本试试

I Started a new project with Spring Boot 1.2.3. I'm getting error

java.lang.NoClassDefFoundError: javax/servlet/Filter

Gradle Dependencies:

dependencies {compile("org.springframework.boot:spring-boot-starter-actuator")compile("org.springframework.boot:spring-boot-starter-data-jpa")compile("org.springframework.boot:spring-boot-starter-security")compile("org.springframework.boot:spring-boot-starter-thymeleaf")compile("org.springframework.boot:spring-boot-starter-web")compile("org.codehaus.groovy:groovy")compile("com.h2database:h2")compile("org.thymeleaf.extras:thymeleaf-extras-springsecurity3")providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")testCompile("org.springframework.boot:spring-boot-starter-test")compile 'org.webjars:jquery:2.1.4'compile 'org.webjars:bootstrap:3.3.4'
}

Here is the full stack trace

Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/Filterat java.lang.ClassLoader.defineClass1(Native Method)at java.lang.ClassLoader.defineClass(ClassLoader.java:800)at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)at java.net.URLClassLoader.access$100(URLClassLoader.java:71)at java.net.URLClassLoader$1.run(URLClassLoader.java:361)at java.net.URLClassLoader$1.run(URLClassLoader.java:355)at java.security.AccessController.doPrivileged(Native Method)at java.net.URLClassLoader.findClass(URLClassLoader.java:354)at java.lang.ClassLoader.loadClass(ClassLoader.java:425)at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)at java.lang.ClassLoader.loadClass(ClassLoader.java:358)at java.lang.ClassLoader.defineClass1(Native Method)at java.lang.ClassLoader.defineClass(ClassLoader.java:800)at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)at java.net.URLClassLoader.access$100(URLClassLoader.java:71)at java.net.URLClassLoader$1.run(URLClassLoader.java:361)at java.net.URLClassLoader$1.run(URLClassLoader.java:355)at java.security.AccessController.doPrivileged(Native Method)at java.net.URLClassLoader.findClass(URLClassLoader.java:354)at java.lang.ClassLoader.loadClass(ClassLoader.java:425)at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)at java.lang.ClassLoader.loadClass(ClassLoader.java:358)at java.lang.Class.getDeclaredMethods0(Native Method)at java.lang.Class.privateGetDeclaredMethods(Class.java:2570)at java.lang.Class.getMethod0(Class.java:2813)at java.lang.Class.getMethod(Class.java:1663)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:125)
Caused by: java.lang.ClassNotFoundException: javax.servlet.Filterat java.net.URLClassLoader$1.run(URLClassLoader.java:366)at java.net.URLClassLoader$1.run(URLClassLoader.java:355)at java.security.AccessController.doPrivileged(Native Method)at java.net.URLClassLoader.findClass(URLClassLoader.java:354)at java.lang.ClassLoader.loadClass(ClassLoader.java:425)at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)at java.lang.ClassLoader.loadClass(ClassLoader.java:358)... 29 moreProcess finished with exit code 1

for the maven users, comment the scope provided in the following dependency:

    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><!--<scope>provided</scope>--></dependency>

UPDATE

As feed.me mentioned you have to uncomment the provided part depending on what kind of app you are deploying.

Here is a useful link with the details: http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#build-tool-plugins-maven-packaging

It's important to make this dependency "provided" again before building a war file! Otherwise the war file will crash when it gets deployed (happend to me with tomcat)

http://stackoverflow.com/questions/30374316/spring-boot-java-lang-noclassdeffounderror-javax-servlet-filter

Springboot project runs fine when running from terminal using command mvn spring-boot:run

Running from Intellij is when I was getting an exception. I changed the spring-boot-starter-tomcat in pom.xml to an older version and it runs without any exception. I think the issue was with compatibly for latest maven embed tomcat 1.2.5.RELEASE.

Now I am using below in my pom.xml

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><version>1.2.4.RELEASE</version></dependency>

http://stackoverflow.com/questions/31494183/getting-a-caused-by-java-lang-noclassdeffounderror-javax-servlet-http-httpser