anchor.diff:  
   
   [[boot-features-customizing-configurableembeddedservletcontainerfactory-directly]]
  -===== Customizing ConfigurableEmbeddedServletContainerFactory directly
  +===== Customizing ConfigurableEmbeddedServletContainer directly
   If the above customization techniques are too limited, you can register the
   `TomcatEmbeddedServletContainerFactory` or `JettyEmbeddedServletContainerFactory` bean
   yourself.
  
positive.code: 	private static class MyCustomizer implements EmbeddedServletContainerCustomizer {
  
  		@Override
  		public void customize(ConfigurableEmbeddedServletContainer factory) {
              factory.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
  		}
  
  	}
  
negative.code: If you need to configure your embdedded servlet container programmatically you can register
  a Spring bean that implements the `EmbeddedServletContainerCustomizer` interface.
  `EmbeddedServletContainerCustomizer` provides access to the
  `ConfigurableEmbeddedServletContainer` which includes numerous customization setter
  methods.
  
  [source,java,indent=0]
  ----
  