Add a Servlet Filter in a Spring Boot application

When using Spring Boot

As mentioned in the reference documentation, the only step needed is to declare that filter as a Bean in a configuration class, that’s it!

@Configuration
public class WebConfig {

  @Bean
  public Filter shallowEtagHeaderFilter() {
    return new ShallowEtagHeaderFilter();
  }
}

When using Spring MVC

You’re probably already extending a WebApplicationInitializer. If not, then you should convert your webapp configuration from a web.xml file to a WebApplicationInitializer class.

If your context configuration lives in XML file(s), you can create a class that extends AbstractDispatcherServletInitializer – if using configuration classes, AbstractAnnotationConfigDispatcherServletInitializer is the proper choice.

In any case, you can then add Filter registration:

  @Override
  protected Filter[] getServletFilters() {
    return new Filter[] {
      new ShallowEtagHeaderFilter();
    };
  }

Full examples of code-based Servlet container initialization are available in the Spring reference documentation.