一、<mvc:annotation-driven />配置在什么时候必须配置？
1、配置了视图映射 view-controller
直接配置响应的页面：无需经过控制器来执行结果 ；但会导致其他请求路径失效，需要配置mvc:annotation-driven标签
<mvc:view-controller path="/success" view-name="success"/>
2、配置了静态资源
RESTful-CRUD操作，删除时，通过jQuery执行delete请求时，找不到静态资源，需要配置mvc:annotation-driven标签
< mvc:default-servlet-handler /> 将在 SpringMVC 上下文中定义一个 DefaultServletHttpRequestHandler，它会对进入 DispatcherServlet 的请求进行筛查，如果发现是没有经过映射的请求，就将该请求交由 WEB 应用服务器默认的 Servlet 处理，如果不是静态资源的请求，才由 DispatcherServlet 继续处理。
3、配置了类型转换器
配置类型转换器服务时，需要指定转换器服务引用
<mvc:annotation-driven conversion-service=“conversionService”/>
会将自定义的ConversionService 注册到 Spring MVC 的上下文中
4、完成 JSR 303 数据验证，也需要配置
二、关于 <mvc:annotation-driven /> 作用
1、<mvc:annotation-driven /> 会自动注册下面的组件：
RequestMappingHandlerMapping
RequestMappingHandlerAdapter
ExceptionHandlerExceptionResolver
还将提供以下支持：
① 支持使用 ConversionService 实例对表单参数进行类型转换
② 支持使用 @NumberFormat 注解、@DateTimeFormat 注解完成数据类型的格式化
③ 支持使用 @Valid 注解对 JavaBean 实例进行 JSR 303 验证
④ 支持使用 @RequestBody 和 @ResponseBody 注解
2、源码参考：
BeanDefinitionParse 用于解析 xml 文件中的标签
继承树结构：
AnnotationDrivenBeanDefinitionParser 用于解析 <mvc: annotation-driven /> 标签
AnnotationDrivenBeanDefinitionParser 源码参考：
class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
public static final String CONTENT_NEGOTIATION_MANAGER_BEAN_NAME = "mvcContentNegotiationManager";
private static final boolean javaxValidationPresent =
ClassUtils.isPresent("javax.validation.Validator", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
private static boolean romePresent =
ClassUtils.isPresent("com.rometools.rome.feed.WireFeed", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
private static final boolean jaxb2Present =
ClassUtils.isPresent("javax.xml.bind.Binder", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
private static final boolean jackson2Present =
ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", AnnotationDrivenBeanDefinitionParser.class.getClassLoader()) &&
ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
private static final boolean jackson2XmlPresent =
ClassUtils.isPresent("com.fasterxml.jackson.dataformat.xml.XmlMapper", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
private static final boolean gsonPresent =
ClassUtils.isPresent("com.google.gson.Gson", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
Object source = parserContext.extractSource(element);
CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
parserContext.pushContainingComponent(compDefinition);
RuntimeBeanReference contentNegotiationManager = getContentNegotiationManager(element, source, parserContext);
RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
handlerMappingDef.setSource(source);
handlerMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
handlerMappingDef.getPropertyValues().add("order", 0);
handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
String methodMappingName = parserContext.getReaderContext().registerWithGeneratedName(handlerMappingDef);
if (element.hasAttribute("enable-matrix-variables")) {
Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enable-matrix-variables"));
handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
}
else if (element.hasAttribute("enableMatrixVariables")) {
Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enableMatrixVariables"));
handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
}
configurePathMatchingProperties(handlerMappingDef, element, parserContext);
RuntimeBeanReference conversionService = getConversionService(element, source, parserContext);
RuntimeBeanReference validator = getValidator(element, source, parserContext);
RuntimeBeanReference messageCodesResolver = getMessageCodesResolver(element);
RootBeanDefinition bindingDef = new RootBeanDefinition(ConfigurableWebBindingInitializer.class);
bindingDef.setSource(source);
bindingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
bindingDef.getPropertyValues().add("conversionService", conversionService);
bindingDef.getPropertyValues().add("validator", validator);
bindingDef.getPropertyValues().add("messageCodesResolver", messageCodesResolver);
ManagedList<?> messageConverters = getMessageConverters(element, source, parserContext);
ManagedList<?> argumentResolvers = getArgumentResolvers(element, parserContext);
ManagedList<?> returnValueHandlers = getReturnValueHandlers(element, parserContext);
String asyncTimeout = getAsyncTimeout(element);
RuntimeBeanReference asyncExecutor = getAsyncExecutor(element);
ManagedList<?> callableInterceptors = getCallableInterceptors(element, source, parserContext);
ManagedList<?> deferredResultInterceptors = getDeferredResultInterceptors(element, source, parserContext);
RootBeanDefinition handlerAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);
handlerAdapterDef.setSource(source);
handlerAdapterDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
handlerAdapterDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
handlerAdapterDef.getPropertyValues().add("webBindingInitializer", bindingDef);
handlerAdapterDef.getPropertyValues().add("messageConverters", messageConverters);
addResponseBodyAdvice(handlerAdapterDef);
if (element.hasAttribute("ignore-default-model-on-redirect")) {
Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignore-default-model-on-redirect"));
handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
}
else if (element.hasAttribute("ignoreDefaultModelOnRedirect")) {
// "ignoreDefaultModelOnRedirect" spelling is deprecated
Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignoreDefaultModelOnRedirect"));
handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
}
if (argumentResolvers != null) {
handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
}
if (returnValueHandlers != null) {
handlerAdapterDef.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
}
if (asyncTimeout != null) {
handlerAdapterDef.getPropertyValues().add("asyncRequestTimeout", asyncTimeout);
}
if (asyncExecutor != null) {
handlerAdapterDef.getPropertyValues().add("taskExecutor", asyncExecutor);
}
handlerAdapterDef.getPropertyValues().add("callableInterceptors", callableInterceptors);
handlerAdapterDef.getPropertyValues().add("deferredResultInterceptors", deferredResultInterceptors);
String handlerAdapterName = parserContext.getReaderContext().registerWithGeneratedName(handlerAdapterDef);
String uriCompContribName = MvcUriComponentsBuilder.MVC_URI_COMPONENTS_CONTRIBUTOR_BEAN_NAME;
RootBeanDefinition uriCompContribDef = new RootBeanDefinition(CompositeUriComponentsContributorFactoryBean.class);
uriCompContribDef.setSource(source);
uriCompContribDef.getPropertyValues().addPropertyValue("handlerAdapter", handlerAdapterDef);
uriCompContribDef.getPropertyValues().addPropertyValue("conversionService", conversionService);
parserContext.getReaderContext().getRegistry().registerBeanDefinition(uriCompContribName, uriCompContribDef);
RootBeanDefinition csInterceptorDef = new RootBeanDefinition(ConversionServiceExposingInterceptor.class);
csInterceptorDef.setSource(source);
csInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, conversionService);
RootBeanDefinition mappedCsInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
mappedCsInterceptorDef.setSource(source);
mappedCsInterceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
mappedCsInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, (Object) null);
mappedCsInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, csInterceptorDef);
String mappedInterceptorName = parserContext.getReaderContext().registerWithGeneratedName(mappedCsInterceptorDef);
RootBeanDefinition exceptionHandlerExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);
exceptionHandlerExceptionResolver.setSource(source);
exceptionHandlerExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
exceptionHandlerExceptionResolver.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
exceptionHandlerExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
exceptionHandlerExceptionResolver.getPropertyValues().add("order", 0);
addResponseBodyAdvice(exceptionHandlerExceptionResolver);
String methodExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(exceptionHandlerExceptionResolver);
RootBeanDefinition responseStatusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);
responseStatusExceptionResolver.setSource(source);
responseStatusExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
responseStatusExceptionResolver.getPropertyValues().add("order", 1);
String responseStatusExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(responseStatusExceptionResolver);
RootBeanDefinition defaultExceptionResolver = new RootBeanDefinition(DefaultHandlerExceptionResolver.class);
defaultExceptionResolver.setSource(source);
defaultExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
defaultExceptionResolver.getPropertyValues().add("order", 2);
String defaultExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(defaultExceptionResolver);
parserContext.registerComponent(new BeanComponentDefinition(handlerMappingDef, methodMappingName));
parserContext.registerComponent(new BeanComponentDefinition(handlerAdapterDef, handlerAdapterName));
parserContext.registerComponent(new BeanComponentDefinition(uriCompContribDef, uriCompContribName));
parserContext.registerComponent(new BeanComponentDefinition(exceptionHandlerExceptionResolver, methodExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(responseStatusExceptionResolver, responseStatusExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(defaultExceptionResolver, defaultExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(mappedCsInterceptorDef, mappedInterceptorName));
// Ensure BeanNameUrlHandlerMapping (SPR-8289) and default HandlerAdapters are not "turned off"
MvcNamespaceUtils.registerDefaultComponents(parserContext, source);
parserContext.popAndRegisterContainingComponent();
return null;
}
...
}
三、以访问静态和动态资源为例
只要请求不好使就可以配置 <mvc:annotation-driven /> 标签
1、既不配置 <mvc:default-servlet-handler>，也不配置 <mvc:annotation-driven />
效果：@RequestMapping映射的资源能访问，静态资源.html/.js/.img 不能访问
通过 DispatcherServlet 中 dispatch 方法追踪源码：
handlerMappings：
当发送请求的时候，会按照顺序依次执行 handlerMappings；
BeanNameUrlHandlerMapping 里面没有保存任何映射信息；
DefaultAnnotationHandlerMapping 里面保存了映射信息：
动态资源能访问：DefaultAnnotationHandlerMapping 里面的 handlerMap 中保存了每一个资源的映射信息；
静态资源不能访问：就是 handlerMap 中没有保存静态资源映射的请求；
handlerAdapters：执行适配器
与此同时 AnnotationMethodHandlerAdapter 帮我们执行目标方法；（过时的）
另外：conversionService是null(类型转换器是不起作用的)
2、只配置 <mvc:default-servlet-handler>，不配置 <mvc:annotation-driven />
效果：静态资源.html/.js/.img 能访问，动态资源不能访问
handlerMappings：
动态资源不能访问原因：DefaultAnnotationHandlerMapping 没有了，用 SimpleUrlHandlerMapping 替换了，将所有请求直接交给 Tomcat；
静态资源能访问： SimpleUrlHandlerMapping 把所有请求都映射给 Tomcat；
handlerAdapter:
AnnotationMethodHandlerAdapter 没有了，替换成了 SimpleControllerHandlerAdapter。
3、既配置 <mvc:default-servlet-handler>，也配置 <mvc:annotation-driven />
效果：动态资源和静态资源都能访问
handlerMappings：
RequestMappingHandlerMapping：用于处理动态请求；
SimpleUrlHandlerMapping ：将请求直接交给Tomcat，有他，静态资源就没问题；
先用 RequestMappingHandlerMapping 处理动态请求，如果能找到映射信息，进行处理；如果找不到，使用 SimpleUrlHandlerMapping 交给Tomcat 处理。
handlerAdapters：
原来的 AnnotationMethodHandlerAdapter 被换成 RequestMappingHandlerAdapter
AnnotationMethodHandlerAdapter已经过时，Spring3.2推荐RequestMappingHandlerAdapter来替代。所以说，默认情况下，没有配置这两个配置时，HelloWorld 程序可以正常运行，但是，涉及到静态资源查找的时候，就必须配置这个 < mvc:annotation-driven /> 配置了。
