如何在SpringBoot下注册一个Filter

两种方式
第一种通过FilterRegistrationBean

 @Bean
 public FilterRegistrationBean filterRegistrationBean(){
    return new FilterRegistrationBean(errorPageFilter());
 }

@Bean
public Filter errorPageFilter(){
  ErrorPageFilter errorPageFilter = new ErrorPageFilter();
  ErrorPage notFind = new ErrorPage("/404");
  errorPageFilter.addErrorPages(notFind);
  return errorPageFilter;
}

第二种通过DelegatingFilterProxyRegistrationBean

@Bean
public DelegatingFilterProxyRegistrationBean delegatingFilterProxyRegistrationBean(){
  return new DelegatingFilterProxyRegistrationBean("errorPageFilter");
}

@Bean("errorPageFilter")
public Filter errorPageFilter(){
  ErrorPageFilter errorPageFilter = new ErrorPageFilter();
  ErrorPage notFind = new ErrorPage("/404");
  errorPageFilter.addErrorPages(notFind);
  return errorPageFilter;
}

二者都是继承同一个父类AbstractFilterRegistrationBean，只是DelegatingFilterProxyRegistrationBean还实现了ApplicationContextAware，注入了ApplicationContext实例，用于查找指定的Filter实例，最终构建的是一个代理Filter实例(DelegatingFilterProxy);FilterRegistrationBean中维护的是目标Filter，结果都是将Filter注册到ServletContext中，推荐使用FilterRegistrationBean。