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
}