@RefreshScope GenericFilterBean will fail to initialize

[dantesun]

@Bean
    @RefreshScope
    public Filter myFilter(AutowireCapableBeanFactory beanFactory) {
        return new GenericFilterBean() {
            @Override
            public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
                chain.doFilter(request, response);
            }
        };
    }

will cause the following exceptions:

java.lang.NullPointerException: null
    at org.springframework.web.filter.GenericFilterBean.init(GenericFilterBean.java:176) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:109) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4561) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5204) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:152) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1403) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1393) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_31]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_31]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_31]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_31]

Because GenericFilterBean will be created as a CGLIB proxy and it's 'logger' instance will be null.

    public final void init(FilterConfig filterConfig) throws ServletException {
        Assert.notNull(filterConfig, "FilterConfig must not be null");
        if (logger.isDebugEnabled()) {
            logger.debug("Initializing filter '" + filterConfig.getFilterName() + "'");
        }

[dsyer]

That's weird isn't it, and easy to reproduce? It must be to do with the fact that it's a Filter I think (so it is initialized very early), because otherwise I see no reason for the logger to be null.

Of course there's no terribly good reason for a Filter to be in @RefreshScope and I expect you can always refactor your code to put the scope annotation on something else and inject it into the filter.

[wilkinsona]

There's nothing in Spring Boot involved in the apparently problematic proxying of GenericFilterBean . @dantesun If you'd like to pursue this (and as @dsyer explain above, we can see no reason for a Filter to be in @RefreshScope), please raise a Spring Framework issue.

[bartboersma]

Same issue when applying an io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker annotation around the doFilterInternal method.

[swethavemuri]

I had the same issue with a custom RequestContextFilter implementation and using de.codecentric chaos-monkey-spring-boot dependency and @RefreshScope. I fixed it by adding the below @Bean in the config class annotated with @RefreshScope.

@Order(Ordered.HIGHEST_PRECEDENCE)
@Bean 
public FilterRegistrationBean contextFilterRegistrationBean() {
          FilterRegistrationBean registrationBean = new FilterRegistrationBean<>();
          CustomFilter contextFilter = new CustomFilter();
          registrationBean.setFilter(contextFilter);
          registrationBean.setOrder(1);
          return registrationBean;
}