Spring boot的@Configuration

　　就在我惊艳于spring 4的AbstractAnnotationConfigDispatcherServletInitializer小巧简洁（如下）的时候却发现spring boot下面竟然无效。

 public class Initializer extends AbstractAnnotationConfigDispatcherServletInitializer {

     @Override
     protected String[] getServletMappings() {
         return new String[] { "/" };
     }

     @Override
     protected Class<?>[] getRootConfigClasses() {
         return new Class[] { TracingConfiguration.class, AppConfiguration.class };
     }

     /** Ensures tracing is setup for all HTTP requests. */
     @Override
     protected Filter[] getServletFilters() {
         return new Filter[] { new DelegatingTracingFilter() };
     }

     @Override
     protected Class<?>[] getServletConfigClasses() {
         // TODO Auto-generated method stub
         return null;
     }
 }

　　后来经过调研发现其实是需要通过@Configuration（注意类级别注解）的类来进行处理，比如下例就是通过FilterRegistrationBean 来指定filter（相当于上面的getServletFilters函数）：

 @Configuration
 public class AppConfiguration {
     @Autowired
     private AutowireCapableBeanFactory beanFactory;

     @Bean
     public FilterRegistrationBean myFilter() {
         FilterRegistrationBean registration = new FilterRegistrationBean();
         Filter myFilter = new DelegatingTracingFilter();
         beanFactory.autowireBean(myFilter);
         registration.setFilter(myFilter);
         //registration.addUrlPatterns("/myfilterpath/*");
         return registration;
     }
 }

　　与之类似的还有下面的bean定义对应于原生Spring的servlet以及多个Filter：

 @Bean
 public ServletRegistrationBean dispatcherServlet() {
     ServletRegistrationBean registration = new ServletRegistrationBean(
             new DispatcherServlet(), "/");
     registration.setAsyncSupported(true);
     return registration;
 }

 @Bean
 public Filter compositeFilter() {
     CompositeFilter compositeFilter = new CompositeFilter();
     compositeFilter.setFilters(ImmutableList.of(new CorsFilter(), shiroFilter));
     return compositeFilter
 }