按照@philwebb说法，嵌入式环境下，SpringBoot有意忽略javax.servlet.ServletContainerInitializer，原因：

The search algorithm used by the containers was problematic. It also causes problems when you want to develop an executable WAR as you often want a javax.servlet.ServletContainerInitializer for the WAR that is not executed when you run java -jar.

解决方案：

1. 注册org.springframework.boot.context.embedded.ServletContextInitializer类型的Bean代替ServletContainerInitializer。

2. 直接向容器注册Servlet和Filter。

3. 向容器注册ServletRegistrationBean和FilterRegistrationBean。

参考：

[1]https://github.com/spring-projects/spring-boot/issues/321

[2]https://github.com/spring-projects/spring-boot/issues/522