spring boot中慎用@EnableWebMvc
什么情况？我为了自定义了一个HandlerInterceptor，非常普通的做法，先是继承了WebMvcConfigurerAdapter，再添加了@EnableWebMvc。注：本篇基于spring-webmvc 4.3.9版本。
@EnableWebMvc
@Configuration
public class XXXAutoConfiguration extends WebMvcConfigurerAdapter {
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new XXXInterceptor());
}
}运行起来之后：一会是ExceptionHandlerExceptionResolver失效，一会是HttpMessageConverters（由RequestMappingHandlerAdapter管理）报错，整个spring mvc环境都混乱了。
呵呵，恭喜你，真的摊上事了！
这就是spring-boot的奥秘，不知不觉中犯错，你以为是这样的，其实你根本就不了解源码（原理）！
不卖关子了！开始分析源码吧！
@EnableWebMvc开启后，意味着springmvc环境被你完全接管了（若不定义需要那些bean，确实啥都没有）。而WebMvcAutoConfiguration原本是自动装配的（注入一系列mvc的bean），影响它失效最重要的原因在于：@ConditionalOnMissingBean(WebMvcConfigurationSupport.class) ，是的，正是Condition发挥了的作用（Ioc容器中已经有了WebMvcConfigurationSupport，那WebMvcAutoConfiguration就不会再实例化注入）。
而WebMvcAutoConfiguration 原本是通过spring-boot-autoconfigure-2.0.5.RELEASE.jar/META-INF/spring.factories自动装配的。
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}
@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
@Autowired(required = false)
public void setConfigurers(List configurers) {
if (!CollectionUtils.isEmpty(configurers)) {
this.configurers.addWebMvcConfigurers(configurers);
}
}
}
public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
}
@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class,
WebMvcConfigurerAdapter.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)//看这里吧
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {
public static final String DEFAULT_PREFIX = "";
public static final String DEFAULT_SUFFIX = "";
@Bean
@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
return new OrderedHiddenHttpMethodFilter();
}
@Bean
@ConditionalOnMissingBean(HttpPutFormContentFilter.class)
@ConditionalOnProperty(prefix = "spring.mvc.formcontent.putfilter", name = "enabled", matchIfMissing = true)
public OrderedHttpPutFormContentFilter httpPutFormContentFilter() {
return new OrderedHttpPutFormContentFilter();
}
// Defined as a nested config to ensure WebMvcConfigurerAdapter is not read when not
// on the classpath
@Configuration
@Import(EnableWebMvcConfiguration.class)
@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
public static class WebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter {
private static final Log logger = LogFactory
.getLog(WebMvcConfigurerAdapter.class);
private final ResourceProperties resourceProperties;
private final WebMvcProperties mvcProperties;
private final ListableBeanFactory beanFactory;
private final HttpMessageConverters messageConverters;
final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;
public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties,
WebMvcProperties mvcProperties, ListableBeanFactory beanFactory,
@Lazy HttpMessageConverters messageConverters,
ObjectProvider resourceHandlerRegistrationCustomizerProvider) {
this.resourceProperties = resourceProperties;
this.mvcProperties = mvcProperties;
this.beanFactory = beanFactory;
this.messageConverters = messageConverters;
this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider
.getIfAvailable();
}
@Override
public void configureMessageConverters(List> converters) {
converters.addAll(this.messageConverters.getConverters());
}
@Override
public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
Long timeout = this.mvcProperties.getAsync().getRequestTimeout();
if (timeout != null) {
configurer.setDefaultTimeout(timeout);
}
}
@Override
public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
Map mediaTypes = this.mvcProperties.getMediaTypes();
for (Entry mediaType : mediaTypes.entrySet()) {
configurer.mediaType(mediaType.getKey(), mediaType.getValue());
}
}
@Bean
@ConditionalOnMissingBean
public InternalResourceViewResolver defaultViewResolver() {
InternalResourceViewResolver resolver = new InternalResourceViewResolver();
resolver.setPrefix(this.mvcProperties.getView().getPrefix());
resolver.setSuffix(this.mvcProperties.getView().getSuffix());
return resolver;
}
@Bean
@ConditionalOnBean(View.class)
@ConditionalOnMissingBean
public BeanNameViewResolver beanNameViewResolver() {
BeanNameViewResolver resolver = new BeanNameViewResolver();
resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
return resolver;
}
@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;
}
@Bean
@ConditionalOnMissingBean
@ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
public LocaleResolver localeResolver() {
if (this.mvcProperties
.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
return new FixedLocaleResolver(this.mvcProperties.getLocale());
}
AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
return localeResolver;
}
@Bean
@ConditionalOnProperty(prefix = "spring.mvc", name = "date-format")
public Formatter dateFormatter() {
return new DateFormatter(this.mvcProperties.getDateFormat());
}
@Override
public MessageCodesResolver getMessageCodesResolver() {
if (this.mvcProperties.getMessageCodesResolverFormat() != null) {
DefaultMessageCodesResolver resolver = new DefaultMessageCodesResolver();
resolver.setMessageCodeFormatter(
this.mvcProperties.getMessageCodesResolverFormat());
return resolver;
}
return null;
}
@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 Collection getBeansOfType(Class type) {
return this.beanFactory.getBeansOfType(type).values();
}
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
if (!this.resourceProperties.isAddMappings()) {
logger.debug("Default resource handling disabled");
return;
}
Integer cachePeriod = this.resourceProperties.getCachePeriod();
if (!registry.hasMappingForPattern("/webjars/**")) {
customizeResourceHandlerRegistration(
registry.addResourceHandler("/webjars/**")
.addResourceLocations(
"classpath:/META-INF/resources/webjars/")
.setCachePeriod(cachePeriod));
}
String staticPathPattern = this.mvcProperties.getStaticPathPattern();
if (!registry.hasMappingForPattern(staticPathPattern)) {
customizeResourceHandlerRegistration(
registry.addResourceHandler(staticPathPattern)
.addResourceLocations(
this.resourceProperties.getStaticLocations())
.setCachePeriod(cachePeriod));
}
}
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(
ResourceProperties resourceProperties) {
return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
this.mvcProperties.getStaticPathPattern());
}
private void customizeResourceHandlerRegistration(
ResourceHandlerRegistration registration) {
if (this.resourceHandlerRegistrationCustomizer != null) {
this.resourceHandlerRegistrationCustomizer.customize(registration);
}
}
@Bean
@ConditionalOnMissingBean({ RequestContextListener.class,
RequestContextFilter.class })
public static RequestContextFilter requestContextFilter() {
return new OrderedRequestContextFilter();
}
@Configuration
@ConditionalOnProperty(value = "spring.mvc.favicon.enabled", matchIfMissing = true)
public static class FaviconConfiguration {
private final ResourceProperties resourceProperties;
public FaviconConfiguration(ResourceProperties resourceProperties) {
this.resourceProperties = resourceProperties;
}
@Bean
public SimpleUrlHandlerMapping faviconHandlerMapping() {
SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1);
mapping.setUrlMap(Collections.singletonMap("**/favicon.ico",
faviconRequestHandler()));
return mapping;
}
@Bean
public ResourceHttpRequestHandler faviconRequestHandler() {
ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler();
requestHandler
.setLocations(this.resourceProperties.getFaviconLocations());
return requestHandler;
}
}
}
/**
* Configuration equivalent to {@code @EnableWebMvc}.
*/
@Configuration
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
@Bean
@Override
public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter();
adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null ? true
: this.mvcProperties.isIgnoreDefaultModelOnRedirect());
return adapter;
}
@Override
protected RequestMappingHandlerAdapter createRequestMappingHandlerAdapter() {
if (this.mvcRegistrations != null
&& this.mvcRegistrations.getRequestMappingHandlerAdapter() != null) {
return this.mvcRegistrations.getRequestMappingHandlerAdapter();
}
return super.createRequestMappingHandlerAdapter();
}
@Bean
@Primary
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
// Must be @Primary for MvcUriComponentsBuilder to work
return super.requestMappingHandlerMapping();
}
@Bean
@Override
public Validator mvcValidator() {
if (!ClassUtils.isPresent("javax.validation.Validator",
getClass().getClassLoader())) {
return super.mvcValidator();
}
return WebMvcValidator.get(getApplicationContext(), getValidator());
}
}
} 那如果我真的要使用@EnableWebMvc的话，这推荐：
- @EnableWebMvc+extends WebMvcConfigurerAdapter，在扩展的类中重写父类的方法即可（想想xml的时代缺啥加啥）