Spring Boot java.lang.NoClassDefFoundError: javax/servlet/Filter

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