<mvc:annotation-driven>注册了什么

前言

上一篇文章dispatcherservlet初始化中提到，如果没有配置handlermapping就会采取默认的策略进行配置handlermapping，这篇文章就要讲述mvc:annotation-driven对默认策略的改变。它背后到底注册了哪些HandlerMapping和HandlerAdapter。

1. 配置mvc:annotation-driven

在dispatcherservlet对应的配置文件上有这样一段配置

    <mvc:annotation-driven />

    <aop:aspectj-autoproxy proxy-target-class="true"/>

    <mvc:interceptors>
        <ref bean="performanceLogInterceptor"></ref>
        <ref bean="concurrentCtrlInterceptor"></ref>
        <ref bean="authenticationInterceptor"></ref>
        <ref bean="authorityInterceptor"></ref>
        <ref bean="tpsControlInterceptor"></ref>
    </mvc:interceptors>

开启了<mvc:annotation-driven/>，然后我们会找到这样的一个实现类AnnotationDrivenBeanDefinitionParser解析处理这个标签

/**
 *这里清清楚楚写着该类是专门处理 <mvc:annotation-driven/>标签的 
 * A {@link BeanDefinitionParser} that provides the configuration for the
 * {@code <annotation-driven/>} MVC namespace element
 *
 *这里说明了注册的HandlerMapping
 * <p>This class registers the following {@link HandlerMapping}s:</p>
 * <ul>
 * <li>{@link RequestMappingHandlerMapping}
 * ordered at 0 for mapping requests to annotated controller methods.
 * <li>{@link BeanNameUrlHandlerMapping}
 * ordered at 2 to map URL paths to controller bean names.
 * </ul>
……
 */
class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {

   ……
}

我们来看看mvc:annotation-driven都注册了哪些东西

    @Override
    public BeanDefinition parse(Element element, ParserContext parserContext) {
        Object source = parserContext.extractSource(element);
        XmlReaderContext readerContext = parserContext.getReaderContext();

        RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);

        ManagedList<?> messageConverters = getMessageConverters(element, source, parserContext);

        RootBeanDefinition handlerAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);

          ……

        RootBeanDefinition exceptionHandlerExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);

        RootBeanDefinition responseStatusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);

        RootBeanDefinition defaultExceptionResolver = new RootBeanDefinition(DefaultHandlerExceptionResolver.class);
   // Ensure BeanNameUrlHandlerMapping (SPR-8289) and default HandlerAdapters are not "turned off"
        MvcNamespaceUtils.registerDefaultComponents(parserContext, source);

        parserContext.popAndRegisterContainingComponent();

        return null;
    }

MvcNamespaceUtils.registerDefaultComponents的内容如下：

public static void registerDefaultComponents(ParserContext parserContext, Object source) {
        registerBeanNameUrlHandlerMapping(parserContext, source);
        registerHttpRequestHandlerAdapter(parserContext, source);
        registerSimpleControllerHandlerAdapter(parserContext, source);
    }

至此所注册的HandlerMapping和HandlerAdapter我们都找到了。