WebAppInitializer cannot be cast to javax.servlet.ServletContainerInitializer

Question

I'm facing the following stacktrace when running mvn tomcat7:run:

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/blog-demo]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:188)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/blog-demo]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    ... 6 more
Caused by: java.lang.ClassCastException: com.replaceme.WebAppInitializer cannot be cast to javax.servlet.ServletContainerInitializer
    at org.apache.catalina.startup.ContextConfig.getServletContainerInitializer(ContextConfig.java:1670)
    at org.apache.catalina.startup.ContextConfig.getServletContainerInitializers(ContextConfig.java:1652)
    at org.apache.catalina.startup.ContextConfig.processServletContainerInitializers(ContextConfig.java:1562)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1270)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:878)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:376)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5322)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more

This is my WebAppInitializer class:

public class WebAppInitializer extends AbstractSecurityWebApplicationInitializer {
    @Override
    public void beforeSpringSecurityFilterChain(ServletContext servletContext) {
        AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();

        ConfigurableEnvironment env = rootContext.getEnvironment();
        env.setDefaultProfiles("production", env.getProperty("user.name"));

        rootContext.scan("com.replaceme.config");

        servletContext.addListener(new ContextLoaderListener(rootContext));

        ServletRegistration.Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(rootContext));
        servlet.setLoadOnStartup(1);
        servlet.addMapping("/");
    }
}

I've added a text file in src/main/resources/META-INF/services called javax.servlet.ServletContainerInitializer which contains the class identifier com.replaceme.WebAppInitializer.

And here are my maven dependencies:

[INFO] +- org.hibernate:hibernate-core:jar:4.3.5.Final:compile
[INFO] |  +- org.jboss.logging:jboss-logging:jar:3.1.3.GA:compile
[INFO] |  +- org.jboss.logging:jboss-logging-annotations:jar:1.2.0.Beta1:compile
[INFO] |  +- org.jboss.spec.javax.transaction:jboss-transaction-api_1.2_spec:jar:1.0.0.Final:compile
[INFO] |  +- dom4j:dom4j:jar:1.6.1:compile
[INFO] |  |  \- xml-apis:xml-apis:jar:1.0.b2:compile
[INFO] |  +- org.hibernate.common:hibernate-commons-annotations:jar:4.0.4.Final:compile
[INFO] |  |  +- (org.jboss.logging:jboss-logging:jar:3.1.3.GA:compile - omitted for duplicate)
[INFO] |  |  \- (org.jboss.logging:jboss-logging-annotations:jar:1.2.0.Beta1:compile - omitted for duplicate)
[INFO] |  +- org.hibernate.javax.persistence:hibernate-jpa-2.1-api:jar:1.0.0.Final:compile
[INFO] |  +- org.javassist:javassist:jar:3.18.1-GA:compile
[INFO] |  +- antlr:antlr:jar:2.7.7:compile
[INFO] |  \- org.jboss:jandex:jar:1.1.0.Final:compile
[INFO] +- org.hibernate:hibernate-validator:jar:5.1.0.Final:compile
[INFO] |  +- javax.validation:validation-api:jar:1.1.0.Final:compile
[INFO] |  +- (org.jboss.logging:jboss-logging:jar:3.1.3.GA:compile - omitted for duplicate)
[INFO] |  \- com.fasterxml:classmate:jar:1.0.0:compile
[INFO] +- ch.qos.logback:logback-classic:jar:1.0.13:runtime
[INFO] |  +- ch.qos.logback:logback-core:jar:1.0.13:runtime
[INFO] |  \- (org.slf4j:slf4j-api:jar:1.7.5:runtime - omitted for duplicate)
[INFO] +- org.slf4j:slf4j-api:jar:1.7.5:compile
[INFO] +- org.slf4j:jcl-over-slf4j:jar:1.7.5:compile
[INFO] |  \- (org.slf4j:slf4j-api:jar:1.7.5:compile - omitted for duplicate)
[INFO] +- org.codehaus.janino:janino:jar:2.6.1:compile
[INFO] |  \- org.codehaus.janino:commons-compiler:jar:2.6.1:compile
[INFO] +- org.springframework:spring-context:jar:4.0.3.RELEASE:compile
[INFO] |  +- org.springframework:spring-aop:jar:4.0.3.RELEASE:compile
[INFO] |  |  +- (aopalliance:aopalliance:jar:1.0:compile - omitted for duplicate)
[INFO] |  |  +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  |  \- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- org.springframework:spring-beans:jar:4.0.3.RELEASE:compile
[INFO] |  |  \- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- org.springframework:spring-core:jar:4.0.3.RELEASE:compile
[INFO] |  \- org.springframework:spring-expression:jar:4.0.3.RELEASE:compile
[INFO] |     \- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] +- org.springframework:spring-jdbc:jar:4.0.3.RELEASE:compile
[INFO] |  +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  \- org.springframework:spring-tx:jar:4.0.3.RELEASE:compile
[INFO] |     +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |     \- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] +- org.springframework:spring-orm:jar:4.0.3.RELEASE:compile
[INFO] |  +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-jdbc:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  \- (org.springframework:spring-tx:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] +- org.springframework:spring-webmvc:jar:4.0.3.RELEASE:compile
[INFO] |  +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-expression:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |  \- org.springframework:spring-web:jar:4.0.3.RELEASE:compile
[INFO] |     +- (org.springframework:spring-aop:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |     +- (org.springframework:spring-beans:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |     +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] |     \- (org.springframework:spring-core:jar:4.0.3.RELEASE:compile - omitted for duplicate)
[INFO] +- org.springframework.security:spring-security-config:jar:3.2.3.RELEASE:compile
[INFO] |  +- aopalliance:aopalliance:jar:1.0:compile
[INFO] |  +- org.springframework.security:spring-security-core:jar:3.2.3.RELEASE:compile
[INFO] |  |  +- (aopalliance:aopalliance:jar:1.0:compile - omitted for duplicate)
[INFO] |  |  +- (org.springframework:spring-aop:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  |  +- (org.springframework:spring-beans:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  |  +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - version managed from 3.2.8.RELEASE; omitted for duplicate)
[INFO] |  |  +- (org.springframework:spring-core:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  |  \- (org.springframework:spring-expression:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-aop:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-beans:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - version managed from 3.2.8.RELEASE; omitted for duplicate)
[INFO] |  \- (org.springframework:spring-core:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] +- org.springframework.security:spring-security-web:jar:3.2.3.RELEASE:compile
[INFO] |  +- (aopalliance:aopalliance:jar:1.0:compile - omitted for duplicate)
[INFO] |  +- (org.springframework.security:spring-security-core:jar:3.2.3.RELEASE:compile - omitted for duplicate)
[INFO] |  +- (org.springframework:spring-beans:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - version managed from 3.2.8.RELEASE; omitted for duplicate)
[INFO] |  +- (org.springframework:spring-core:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-expression:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  \- (org.springframework:spring-web:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] +- org.springframework.data:spring-data-jpa:jar:1.5.2.RELEASE:compile
[INFO] |  +- org.springframework.data:spring-data-commons:jar:1.7.2.RELEASE:compile
[INFO] |  |  +- (org.springframework:spring-core:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  |  +- (org.springframework:spring-beans:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  |  +- (org.slf4j:slf4j-api:jar:1.7.5:compile - version managed from 1.7.6; omitted for duplicate)
[INFO] |  |  \- (org.slf4j:jcl-over-slf4j:jar:1.7.5:runtime - version managed from 1.7.6; omitted for duplicate)
[INFO] |  +- (org.springframework:spring-orm:jar:4.0.3.RELEASE:compile - version managed from 3.2.8.RELEASE; omitted for duplicate)
[INFO] |  +- (org.springframework:spring-context:jar:4.0.3.RELEASE:compile - version managed from 3.2.8.RELEASE; omitted for duplicate)
[INFO] |  +- (org.springframework:spring-aop:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-tx:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-beans:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- (org.springframework:spring-core:jar:3.2.8.RELEASE:compile - omitted for conflict with 4.0.3.RELEASE)
[INFO] |  +- org.aspectj:aspectjrt:jar:1.7.4:compile
[INFO] |  +- (org.slf4j:slf4j-api:jar:1.7.5:compile - version managed from 1.7.6; omitted for duplicate)
[INFO] |  \- (org.slf4j:jcl-over-slf4j:jar:1.7.5:runtime - version managed from 1.7.6; omitted for duplicate)
[INFO] +- javax.servlet:javax.servlet-api:jar:3.1.0:provided
[INFO] +- org.thymeleaf:thymeleaf:jar:2.1.2.RELEASE:compile
[INFO] |  +- ognl:ognl:jar:3.0.6:compile
[INFO] |  +- (org.javassist:javassist:jar:3.16.1-GA:compile - omitted for conflict with 3.18.1-GA)
[INFO] |  \- (org.slf4j:slf4j-api:jar:1.7.5:compile - version managed from 1.6.1; omitted for duplicate)
[INFO] +- org.thymeleaf:thymeleaf-spring4:jar:2.1.2.RELEASE:compile
[INFO] |  +- (org.thymeleaf:thymeleaf:jar:2.1.2.RELEASE:compile - omitted for duplicate)
[INFO] |  \- (org.slf4j:slf4j-api:jar:1.7.5:compile - version managed from 1.6.1; omitted for duplicate)
[INFO] +- cglib:cglib:jar:3.1:compile
[INFO] |  \- org.ow2.asm:asm:jar:4.2:compile

EDIT: It won't work with the following class as well:

public class WebAppInitializer implements WebApplicationInitializer {
    public void onStartup(ServletContext servletContext) throws ServletException {
        AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();

        ConfigurableEnvironment env = rootContext.getEnvironment();
        env.setDefaultProfiles("production", env.getProperty("user.name"));

        rootContext.scan("com.replaceme.config");

        servletContext.addListener(new ContextLoaderListener(rootContext));

        ServletRegistration.Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(rootContext));
        servlet.setLoadOnStartup(1);
        servlet.addMapping("/");
    }
}

Answer 1

A WebApplicationInitializer (from Spring) is not a ServletContainerInitializer (from the Servlet specs). So just remove the file javax.servlet.ServletContainerInitializer from the services folder. Your WebAppInitializer will automatically be detected by Spring (see here)

Answer 2

Class com.replaceme.WebAppInitializer which extends Class AbstractSecurityWebApplicationInitializer is not a subtype of Class javax.servlet.ServletContainerInitializer. So, You are not allowed to type cast an object of one type to an object of another type. To simply say you are trying to convert a dog to a donkey, that's why ClassCastException is thrown. Casting can't be done between object types which are not in the same inheritance tree