SpringBoot--对SpirngMVC的自动配置

SpringBoot对SpringMVC提供了许多自动配置

• Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
• Support for serving static resources, including support for WebJars (covered later in this document)).
• Automatic registration of Converter, GenericConverter, and Formatter beans.
• Support for HttpMessageConverters (covered later in this document).
• Automatic registration of MessageCodesResolver (covered later in this document).
• Static index.html support.
• Custom Favicon support (covered later in this document).
• Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

视图解析器

　　包含了ContentNegotiatingViewResolver和BeanNameViewResolver。

　　在WebMvcAutoConfiguration中定位到ContentNegotiatingViewResolver有关的方法，该方法标注了@Bean，所以会把ContentNegotiatingViewResolver加入容器。根据注释可以看到，ContentNegotiatingViewResolver用于管理所有的ViewResolver，即所有实现了ViewResolver的Bean，然后对于每个View找到最合适的ViewResolver去解析。我们可以向容器中添加自定义视图解析器，添加的自定义视图解析器也会被ContentNegotiatingViewResolver所管理。

        @Bean
        @ConditionalOnBean(ViewResolver.class)
        @ConditionalOnMissingBean(name = "viewResolver",
                value = ContentNegotiatingViewResolver.class)
        public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {
            ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();
            resolver.setContentNegotiationManager(
                    beanFactory.getBean(ContentNegotiationManager.class));
            // ContentNegotiatingViewResolver uses all the other view resolvers to locate
            // a view so it should have a high precedence
            resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
            return resolver;
        }

　　在启动类使用@Bean注解添加自定义ViewResolver，并在doDispatch打上断点，随意发送一个请求，观察ContentNegotiatingViewResolver是否把自定义的myViewResolver收录进去。

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Bean
    public ViewResolver myViewResolver(){
        return new MyViewResolver();
    }

    private static class MyViewResolver implements ViewResolver{

        @Override
        public View resolveViewName(String s, Locale locale) throws Exception {
            return null;
        }
    }
}

静态资源

　　

转换器与格式化器

　　页面表单提交的数据都是String类型的，当注入pojo的时候需要转换成相应的类型，这一工作由conveter完成。日期格式的转换有转换器完成。SpringBoot自动注入这两种类型的Bean是byType的，即从容器中获取所有Converter Formatter类型的bean并调用相应的add方法，所以如果想添加自定义的转换器、格式化器，同样只需要放到容器里即可。

        @Override
        public void addFormatters(FormatterRegistry registry) {
            for (Converter<?, ?> converter : getBeansOfType(Converter.class)) {
                registry.addConverter(converter);
            }
            for (GenericConverter converter : getBeansOfType(GenericConverter.class)) {
                registry.addConverter(converter);
            }
            for (Formatter<?> formatter : getBeansOfType(Formatter.class)) {
                registry.addFormatter(formatter);
            }
        }

        private <T> Collection<T> getBeansOfType(Class<T> type) {
            return this.beanFactory.getBeansOfType(type).values();
        }

HttpMessageConverters

　　需要自定义HttpMessageConverters，只需要把自己定义的HttpMessageConverters放入容器中，SpringBoot会把HttpMessageConverters添加到SpringMVC中。

    @Bean
    public HttpMessageConverters customConverters() {
        HttpMessageConverter<?> additional = ...
        HttpMessageConverter<?> another = ...
        return new HttpMessageConverters(additional, another);
    }