spring

[Spring] MVC 살펴보기

By CodeNexus

Spring Boot Web Mvc에 대해서 알아보자. SpringBoot Web MVC를 알기 위해서 spring-boot-starter-web 을 추가한다.

				<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

/hello로 요청을 했을 때 hello를 리턴하는 HelloController를 만들고, 애플리케이션을 실행한다.

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "hello";
    }
}

localhost:8080/hello 를 주소창에 입력하면, 본문에 hello라고 찍히는 것을 확인할 수 있다.

Web관련된 아무런 설정없이 이런게 가능했던 이유는 뭘까?

Root에 있는 클래스에 있는@SpringBootApplication안에 있는 @EnableAutoConfiguration 이 어노테이션을 통해서 autoconfigurer라이브러리 META-INF/spring.factories에 정의되어있는 수많은 설정파일들이 만들어진다. 특히나 WebMVC는 WebMvcAutoConfiguration 클래스를 통해서 자동 빈 설정을 한다. 아래는 해당 클래스 내용이다. viewResolver, RequestMapping … 등 SpringMVC에 필요한 것들이 정의됨을 알 수 있다.

package org.springframework.boot.autoconfigure.web.servlet;

@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class,
		TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {

	public static final String DEFAULT_PREFIX = "";

	public static final String DEFAULT_SUFFIX = "";

	private static final String[] SERVLET_LOCATIONS = { "/" };

	@Bean
	@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
	@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled",
			matchIfMissing = true)
	public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
		return new OrderedHiddenHttpMethodFilter();
	}

	@Bean
	@ConditionalOnMissingBean(FormContentFilter.class)
	@ConditionalOnProperty(prefix = "spring.mvc.formcontent.filter", name = "enabled",
			matchIfMissing = true)
	public OrderedFormContentFilter formContentFilter() {
		return new OrderedFormContentFilter();
	}

	// Defined as a nested config to ensure WebMvcConfigurer is not read when not
	// on the classpath
	@Configuration
	@Import(EnableWebMvcConfiguration.class)
	@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
	@Order(0)
	public static class WebMvcAutoConfigurationAdapter
			implements WebMvcConfigurer, ResourceLoaderAware {

		private static final Log logger = LogFactory.getLog(WebMvcConfigurer.class);

		private final ResourceProperties resourceProperties;

		private final WebMvcProperties mvcProperties;

		private final ListableBeanFactory beanFactory;

		private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;

		final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;

		private ResourceLoader resourceLoader;

		public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties,
				WebMvcProperties mvcProperties, ListableBeanFactory beanFactory,
				ObjectProvider<HttpMessageConverters> messageConvertersProvider,
				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider) {
			this.resourceProperties = resourceProperties;
			this.mvcProperties = mvcProperties;
			this.beanFactory = beanFactory;
			this.messageConvertersProvider = messageConvertersProvider;
			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider
					.getIfAvailable();
		}

		@Override
		public void setResourceLoader(ResourceLoader resourceLoader) {
			this.resourceLoader = resourceLoader;
		}

		@Override
		public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
			this.messageConvertersProvider.ifAvailable((customConverters) -> converters
					.addAll(customConverters.getConverters()));
		}

		@Override
		public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
			if (this.beanFactory.containsBean(
					TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME)) {
				Object taskExecutor = this.beanFactory.getBean(
						TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME);
				if (taskExecutor instanceof AsyncTaskExecutor) {
					configurer.setTaskExecutor(((AsyncTaskExecutor) taskExecutor));
				}
			}
			Duration timeout = this.mvcProperties.getAsync().getRequestTimeout();
			if (timeout != null) {
				configurer.setDefaultTimeout(timeout.toMillis());
			}
		}

		@Override
		public void configurePathMatch(PathMatchConfigurer configurer) {
			configurer.setUseSuffixPatternMatch(
					this.mvcProperties.getPathmatch().isUseSuffixPattern());
			configurer.setUseRegisteredSuffixPatternMatch(
					this.mvcProperties.getPathmatch().isUseRegisteredSuffixPattern());
		}

		@Override
		public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
			WebMvcProperties.Contentnegotiation contentnegotiation = this.mvcProperties
					.getContentnegotiation();
			configurer.favorPathExtension(contentnegotiation.isFavorPathExtension());
			configurer.favorParameter(contentnegotiation.isFavorParameter());
			if (contentnegotiation.getParameterName() != null) {
				configurer.parameterName(contentnegotiation.getParameterName());
			}
			Map<String, MediaType> mediaTypes = this.mvcProperties.getContentnegotiation()
					.getMediaTypes();
			mediaTypes.forEach(configurer::mediaType);
		}

		@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;
		}

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

		@Override
		public void addResourceHandlers(ResourceHandlerRegistry registry) {
			if (!this.resourceProperties.isAddMappings()) {
				logger.debug("Default resource handling disabled");
				return;
			}
			Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
			CacheControl cacheControl = this.resourceProperties.getCache()
					.getCachecontrol().toHttpCacheControl();
			if (!registry.hasMappingForPattern("/webjars/**")) {
				customizeResourceHandlerRegistration(registry
						.addResourceHandler("/webjars/**")
						.addResourceLocations("classpath:/META-INF/resources/webjars/")
						.setCachePeriod(getSeconds(cachePeriod))
						.setCacheControl(cacheControl));
			}
			String staticPathPattern = this.mvcProperties.getStaticPathPattern();
			if (!registry.hasMappingForPattern(staticPathPattern)) {
				customizeResourceHandlerRegistration(
						registry.addResourceHandler(staticPathPattern)
								.addResourceLocations(getResourceLocations(
										this.resourceProperties.getStaticLocations()))
								.setCachePeriod(getSeconds(cachePeriod))
								.setCacheControl(cacheControl));
			}
		}

		private Integer getSeconds(Duration cachePeriod) {
			return (cachePeriod != null) ? (int) cachePeriod.getSeconds() : null;
		}

		@Bean
		public WelcomePageHandlerMapping welcomePageHandlerMapping(
				ApplicationContext applicationContext) {
			return new WelcomePageHandlerMapping(
					new TemplateAvailabilityProviders(applicationContext),
					applicationContext, getWelcomePage(),
					this.mvcProperties.getStaticPathPattern());
		}

		static String[] getResourceLocations(String[] staticLocations) {
			String[] locations = new String[staticLocations.length
					+ SERVLET_LOCATIONS.length];
			System.arraycopy(staticLocations, 0, locations, 0, staticLocations.length);
			System.arraycopy(SERVLET_LOCATIONS, 0, locations, staticLocations.length,
					SERVLET_LOCATIONS.length);
			return locations;
		}

		private Optional<Resource> getWelcomePage() {
			String[] locations = getResourceLocations(
					this.resourceProperties.getStaticLocations());
			return Arrays.stream(locations).map(this::getIndexHtml)
					.filter(this::isReadable).findFirst();
		}

		private Resource getIndexHtml(String location) {
			return this.resourceLoader.getResource(location + "index.html");
		}

		private boolean isReadable(Resource resource) {
			try {
				return resource.exists() && (resource.getURL() != null);
			}
			catch (Exception ex) {
				return false;
			}
		}

		private void customizeResourceHandlerRegistration(
				ResourceHandlerRegistration registration) {
			if (this.resourceHandlerRegistrationCustomizer != null) {
				this.resourceHandlerRegistrationCustomizer.customize(registration);
			}
		}

		@Bean
		@ConditionalOnMissingBean({ RequestContextListener.class,
				RequestContextFilter.class })
		@ConditionalOnMissingFilterBean(RequestContextFilter.class)
		public static RequestContextFilter requestContextFilter() {
			return new OrderedRequestContextFilter();
		}

		@Configuration
		@ConditionalOnProperty(value = "spring.mvc.favicon.enabled",
				matchIfMissing = true)
		public static class FaviconConfiguration implements ResourceLoaderAware {

			private final ResourceProperties resourceProperties;

			private ResourceLoader resourceLoader;

			public FaviconConfiguration(ResourceProperties resourceProperties) {
				this.resourceProperties = resourceProperties;
			}

			@Override
			public void setResourceLoader(ResourceLoader resourceLoader) {
				this.resourceLoader = resourceLoader;
			}

			@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(resolveFaviconLocations());
				return requestHandler;
			}

			private List<Resource> resolveFaviconLocations() {
				String[] staticLocations = getResourceLocations(
						this.resourceProperties.getStaticLocations());
				List<Resource> locations = new ArrayList<>(staticLocations.length + 1);
				Arrays.stream(staticLocations).map(this.resourceLoader::getResource)
						.forEach(locations::add);
				locations.add(new ClassPathResource("/"));
				return Collections.unmodifiableList(locations);
			}

		}

	}

	/**
	 * Configuration equivalent to {@code @EnableWebMvc}.
	 */
	@Configuration
	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {

		private final WebMvcProperties mvcProperties;

		private final ListableBeanFactory beanFactory;

		private final WebMvcRegistrations mvcRegistrations;

		public EnableWebMvcConfiguration(
				ObjectProvider<WebMvcProperties> mvcPropertiesProvider,
				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider,
				ListableBeanFactory beanFactory) {
			this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
			this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
			this.beanFactory = beanFactory;
		}

		@Bean
		@Override
		public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
			RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter();
			adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null
					|| 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 FormattingConversionService mvcConversionService() {
			WebConversionService conversionService = new WebConversionService(
					this.mvcProperties.getDateFormat());
			addFormatters(conversionService);
			return conversionService;
		}

		@Bean
		@Override
		public Validator mvcValidator() {
			if (!ClassUtils.isPresent("javax.validation.Validator",
					getClass().getClassLoader())) {
				return super.mvcValidator();
			}
			return ValidatorAdapter.get(getApplicationContext(), getValidator());
		}

		@Override
		protected RequestMappingHandlerMapping createRequestMappingHandlerMapping() {
			if (this.mvcRegistrations != null
					&& this.mvcRegistrations.getRequestMappingHandlerMapping() != null) {
				return this.mvcRegistrations.getRequestMappingHandlerMapping();
			}
			return super.createRequestMappingHandlerMapping();
		}

		@Override
		protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
			try {
				return this.beanFactory.getBean(ConfigurableWebBindingInitializer.class);
			}
			catch (NoSuchBeanDefinitionException ex) {
				return super.getConfigurableWebBindingInitializer();
			}
		}

		@Override
		protected ExceptionHandlerExceptionResolver createExceptionHandlerExceptionResolver() {
			if (this.mvcRegistrations != null && this.mvcRegistrations
					.getExceptionHandlerExceptionResolver() != null) {
				return this.mvcRegistrations.getExceptionHandlerExceptionResolver();
			}
			return super.createExceptionHandlerExceptionResolver();
		}

		@Override
		protected void configureHandlerExceptionResolvers(
				List<HandlerExceptionResolver> exceptionResolvers) {
			super.configureHandlerExceptionResolvers(exceptionResolvers);
			if (exceptionResolvers.isEmpty()) {
				addDefaultHandlerExceptionResolvers(exceptionResolvers);
			}
			if (this.mvcProperties.isLogResolvedException()) {
				for (HandlerExceptionResolver resolver : exceptionResolvers) {
					if (resolver instanceof AbstractHandlerExceptionResolver) {
						((AbstractHandlerExceptionResolver) resolver)
								.setWarnLogCategory(resolver.getClass().getName());
					}
				}
			}
		}

		@Bean
		@Override
		public ContentNegotiationManager mvcContentNegotiationManager() {
			ContentNegotiationManager manager = super.mvcContentNegotiationManager();
			List<ContentNegotiationStrategy> strategies = manager.getStrategies();
			ListIterator<ContentNegotiationStrategy> iterator = strategies.listIterator();
			while (iterator.hasNext()) {
				ContentNegotiationStrategy strategy = iterator.next();
				if (strategy instanceof PathExtensionContentNegotiationStrategy) {
					iterator.set(new OptionalPathExtensionContentNegotiationStrategy(
							strategy));
				}
			}
			return manager;
		}

	}

	@Configuration
	@ConditionalOnEnabledResourceChain
	static class ResourceChainCustomizerConfiguration {

		@Bean
		public ResourceChainResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer() {
			return new ResourceChainResourceHandlerRegistrationCustomizer();
		}

	}

	interface ResourceHandlerRegistrationCustomizer {

		void customize(ResourceHandlerRegistration registration);

	}

	static class ResourceChainResourceHandlerRegistrationCustomizer
			implements ResourceHandlerRegistrationCustomizer {

		@Autowired
		private ResourceProperties resourceProperties = new ResourceProperties();

		@Override
		public void customize(ResourceHandlerRegistration registration) {
			ResourceProperties.Chain properties = this.resourceProperties.getChain();
			configureResourceChain(properties,
					registration.resourceChain(properties.isCache()));
		}

		private void configureResourceChain(ResourceProperties.Chain properties,
				ResourceChainRegistration chain) {
			Strategy strategy = properties.getStrategy();
			if (properties.isCompressed()) {
				chain.addResolver(new EncodedResourceResolver());
			}
			if (strategy.getFixed().isEnabled() || strategy.getContent().isEnabled()) {
				chain.addResolver(getVersionResourceResolver(strategy));
			}
			if (properties.isHtmlApplicationCache()) {
				chain.addTransformer(new AppCacheManifestTransformer());
			}
		}

		private ResourceResolver getVersionResourceResolver(
				ResourceProperties.Strategy properties) {
			VersionResourceResolver resolver = new VersionResourceResolver();
			if (properties.getFixed().isEnabled()) {
				String version = properties.getFixed().getVersion();
				String[] paths = properties.getFixed().getPaths();
				resolver.addFixedVersionStrategy(version, paths);
			}
			if (properties.getContent().isEnabled()) {
				String[] paths = properties.getContent().getPaths();
				resolver.addContentVersionStrategy(paths);
			}
			return resolver;
		}

	}

	/**
	 * Decorator to make {@link PathExtensionContentNegotiationStrategy} optional
	 * depending on a request attribute.
	 */
	static class OptionalPathExtensionContentNegotiationStrategy
			implements ContentNegotiationStrategy {

		private static final String SKIP_ATTRIBUTE = PathExtensionContentNegotiationStrategy.class
				.getName() + ".SKIP";

		private final ContentNegotiationStrategy delegate;

		OptionalPathExtensionContentNegotiationStrategy(
				ContentNegotiationStrategy delegate) {
			this.delegate = delegate;
		}

		@Override
		public List<MediaType> resolveMediaTypes(NativeWebRequest webRequest)
				throws HttpMediaTypeNotAcceptableException {
			Object skip = webRequest.getAttribute(SKIP_ATTRIBUTE,
					RequestAttributes.SCOPE_REQUEST);
			if (skip != null && Boolean.parseBoolean(skip.toString())) {
				return MEDIA_TYPE_ALL_LIST;
			}
			return this.delegate.resolveMediaTypes(webRequest);
		}

	}

}

이런 @SpringBootApplication 의 매직때문에 아무것도 하지않아도 간단한 코딩으로 WebApplication을 띄울 수 있었던 것이다.

Spring MVC를 확장하려면 ?

@Configuration + WebMvcConfigurer

@Configuration // 빈으로 등록 되야함
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/m/**")
                .addResourceLocations("classpath:/m/")
                .setCachePeriod(20);
    }

  // 더 overrid해서 사용 가능함
}

Spring MVC를 재정의

@Configuration + @EnableWebMvc

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