SpringBoot中SpringMVC自动配置源码学习笔记

SpringMVC自动配置

源码：
@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 {

	@Bean
	@ConditionalOnBean(ViewResolver.class)
	@ConditionalOnMissingBean(name = "viewResolver", value = ContentNegotiatingViewResolver.class)
	public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {
		//组合所有的视图解析器的
		ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();
		resolver.setContentNegotiationManager(beanFactory.getBean(ContentNegotiationManager.class));
		resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
		return resolver;
	}

ContentNegotiatingViewResolver//组合所有的视图解析器的

		源码：
		//视图解析器(根据方法的返回值得到视图对象(View)，视图对象决定如何渲染(转发?重定向?))
		public class ContentNegotiatingViewResolver extends WebApplicationObjectSupport implements ViewResolver, Ordered, InitializingBean {

			@Override
			@Nullable
			public View resolveViewName(String viewName, Locale locale) throws Exception {
				RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
				Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");
				List<MediaType> requestedMediaTypes = getMediaTypes(((ServletRequestAttributes) attrs).getRequest());
				if (requestedMediaTypes != null) {
					//获取候选视图对象
					List<View> candidateViews = getCandidateViews(viewName, locale, requestedMediaTypes);
					//选择最适合的视图对象
					View bestView = getBestView(candidateViews, requestedMediaTypes, attrs);
					if (bestView != null) {
						return bestView;
					}
				}
				
				private List<View> getCandidateViews(String viewName, Locale locale, List<MediaType> requestedMediaTypes) throws Exception {
					List<View> candidateViews = new ArrayList<>();
					if (this.viewResolvers != null) {
						Assert.state(this.contentNegotiationManager != null, "No ContentNegotiationManager set");
						//把所有视图解析器拿来，解析
						for (ViewResolver viewResolver : this.viewResolvers) {
							View view = viewResolver.resolveViewName(viewName, locale);
							if (view != null) {
								candidateViews.add(view);
							}
							for (MediaType requestedMediaType : requestedMediaTypes) {
								List<String> extensions = this.contentNegotiationManager.resolveFileExtensions(requestedMediaType);
								for (String extension : extensions) {
									String viewNameWithExtension = viewName + '.' + extension;
									view = viewResolver.resolveViewName(viewNameWithExtension, locale);
									if (view != null) {
										candidateViews.add(view);
									}
								}
							}
						}
					}
					if (!CollectionUtils.isEmpty(this.defaultViews)) {
						candidateViews.addAll(this.defaultViews);
					}
					return candidateViews;
				}
			}
		}	
		
	//注册国际化功能
	@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;
	}
	
	//初始化方法
	@Override
	protected void initServletContext(ServletContext servletContext) {
		//从容器中获取所有的视图解析器
		Collection<ViewResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(obtainApplicationContext(), ViewResolver.class).values();
		//把这个解析器作为要组合的所有的视图解析器
		if (this.viewResolvers == null) {
			this.viewResolvers = new ArrayList<>(matchingBeans.size());
			for (ViewResolver viewResolver : matchingBeans) {
				if (this != viewResolver) {
					this.viewResolvers.add(viewResolver);
				}
			}
		}
		else {
			for (int i = 0; i < this.viewResolvers.size(); i++) {
				ViewResolver vr = this.viewResolvers.get(i);
				if (matchingBeans.contains(vr)) {
					continue;
				}
				String name = vr.getClass().getName() + i;
				obtainApplicationContext().getAutowireCapableBeanFactory().initializeBean(vr, name);
			}
		}
		AnnotationAwareOrderComparator.sort(this.viewResolvers);
		this.cnmFactoryBean.setServletContext(servletContext);
	}
	
	//添加格式化器，自己添加的格式化器转换器，我们只需要放在容器中即可
	@Override
	public void addFormatters(FormatterRegistry registry) {
		//Converter转换器，类型转换
		for (Converter<?, ?> converter : getBeansOfType(Converter.class)) {
			registry.addConverter(converter);
		}
		for (GenericConverter converter : getBeansOfType(GenericConverter.class)) {
			registry.addConverter(converter);
		}
		//Formatter格式化器，日期
		for (Formatter<?> formatter : getBeansOfType(Formatter.class)) {
			registry.addFormatter(formatter);
		}
	}
	private <T> Collection<T> getBeansOfType(Class<T> type) {
		//从容器beanFactory中获取所有的Converter
		return this.beanFactory.getBeansOfType(type).values();
	}
	
	@Configuration
	@Import(EnableWebMvcConfiguration.class)
	@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
	@Order(0)
	public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {
	
		private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
		
		//是HttpMessageConverters从容器中确定；获取所有的HttpMessageConverter
		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();
		}
	}	

HttpMessageConverters//是HttpMessageConverters从容器中确定；获取所有的HttpMessageConverter

		源码：
		public class HttpMessageConverters implements Iterable<HttpMessageConverter<?>> {
			
			public HttpMessageConverters(Collection<HttpMessageConverter<?>> additionalConverters) {
				this(true, additionalConverters);
			}
		}
	
	
	//消息解析，从配置类里拿配置
	@Override
	public MessageCodesResolver getMessageCodesResolver() {
		if (this.mvcProperties.getMessageCodesResolverFormat() != null) {
			DefaultMessageCodesResolver resolver = new DefaultMessageCodesResolver();
			resolver.setMessageCodeFormatter(this.mvcProperties.getMessageCodesResolverFormat());
			return resolver;
		}
		return null;
	}

getMessageCodesResolverFormat()

		源码：
		@ConfigurationProperties(prefix = "spring.mvc")
		public class WebMvcProperties {
		
			private DefaultMessageCodesResolver.Format messageCodesResolverFormat;
			
			public DefaultMessageCodesResolver.Format getMessageCodesResolverFormat() {
				return this.messageCodesResolverFormat;
			}
		}

DefaultMessageCodesResolver

			源码：
			@SuppressWarnings("serial")
			public class DefaultMessageCodesResolver implements MessageCodesResolver, Serializable {
				
				//定义错误代码生成规则
				public enum Format implements MessageCodeFormatter {
					/**
					 * Prefix the error code at the beginning of the generated message code. e.g.:
					 * {@code errorCode + "." + object name + "." + field}
					 * 第一种规则(错误代码，对象名，属性名)
					 */					
					PREFIX_ERROR_CODE {
						@Override
						public String format(String errorCode, @Nullable String objectName, @Nullable String field) {
							return toDelimitedString(errorCode, objectName, field);
						}
					},

					/**
					 * Postfix the error code at the end of the generated message code. e.g.:
					 * {@code object name + "." + field + "." + errorCode}
					 * 第二种规则(对象名，属性名，错误代码)
					 */
					POSTFIX_ERROR_CODE {
						@Override
						public String format(String errorCode, @Nullable String objectName, @Nullable String field) {
							return toDelimitedString(objectName, field, errorCode);
						}
					};

					/**
					 * Concatenate the given elements, delimiting each with
					 * {@link DefaultMessageCodesResolver#CODE_SEPARATOR}, skipping zero-length or
					 * null elements altogether.
					 */
					public static String toDelimitedString(String... elements) {
						StringBuilder rtn = new StringBuilder();
						for (String element : elements) {
							if (StringUtils.hasLength(element)) {
								rtn.append(rtn.length() == 0 ? "" : CODE_SEPARATOR);
								rtn.append(element);
							}
						}
						return rtn.toString();
					}
				}			
			}
	//可以配置一个ConfigurableWebBindingInitializer来替换默认的(添加到容器中)
	@Override
	protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
		try {
			return this.beanFactory.getBean(ConfigurableWebBindingInitializer.class);
		}
		catch (NoSuchBeanDefinitionException ex) {
			return super.getConfigurableWebBindingInitializer();
		}
	}

getConfigurableWebBindingInitializer()

		源码：
		//初始化web数据绑定器(WebDataBinder)的,把请求数据绑定到哪，比如到JavaBean
		protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
			ConfigurableWebBindingInitializer initializer = new ConfigurableWebBindingInitializer();
			initializer.setConversionService(mvcConversionService());
			initializer.setValidator(mvcValidator());
			MessageCodesResolver messageCodesResolver = getMessageCodesResolver();
			if (messageCodesResolver != null) {
				initializer.setMessageCodesResolver(messageCodesResolver);
			}
			return initializer;
		}

ConfigurableWebBindingInitializer

			源码：
			//初始化web数据绑定器
			public class ConfigurableWebBindingInitializer implements org.springframework.web.bind.support.WebBindingInitializer {
				@Override
				public void initBinder(WebDataBinder binder) {
					binder.setAutoGrowNestedPaths(this.autoGrowNestedPaths);
					if (this.directFieldAccess) {
						binder.initDirectFieldAccess();
					}
					if (this.messageCodesResolver != null) {
						binder.setMessageCodesResolver(this.messageCodesResolver);
					}
					if (this.bindingErrorProcessor != null) {
						binder.setBindingErrorProcessor(this.bindingErrorProcessor);
					}
					if (this.validator != null && binder.getTarget() != null &&
							this.validator.supports(binder.getTarget().getClass())) {
						binder.setValidator(this.validator);
					}
					if (this.conversionService != null) {
						binder.setConversionService(this.conversionService);
					}
					if (this.propertyEditorRegistrars != null) {
						for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) {
							propertyEditorRegistrar.registerCustomEditors(binder);
						}
					}
				}			
			}
}

DispatcherServlet

	源码：
	@SuppressWarnings("serial")
	public class DispatcherServlet extends FrameworkServlet {
		
		//所有请求进来调用该方法
		protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
			HttpServletRequest processedRequest = request;
			HandlerExecutionChain mappedHandler = null;
			boolean multipartRequestParsed = false;

			WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

			try {
				ModelAndView mv = null;
				Exception dispatchException = null;

				try {
					processedRequest = checkMultipart(request);
					multipartRequestParsed = (processedRequest != request);

					// Determine handler for the current request.
					mappedHandler = getHandler(processedRequest);
					if (mappedHandler == null) {
						noHandlerFound(processedRequest, response);
						return;
					}

					// Determine handler adapter for the current request.
					HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

					// Process last-modified header, if supported by the handler.
					String method = request.getMethod();
					boolean isGet = "GET".equals(method);
					if (isGet || "HEAD".equals(method)) {
						long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
						if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
							return;
						}
					}

					if (!mappedHandler.applyPreHandle(processedRequest, response)) {
						return;
					}

					// Actually invoke the handler.
					mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

					if (asyncManager.isConcurrentHandlingStarted()) {
						return;
					}

					applyDefaultViewName(processedRequest, mv);
					mappedHandler.applyPostHandle(processedRequest, response, mv);
				}
				catch (Exception ex) {
					dispatchException = ex;
				}
				catch (Throwable err) {
					// As of 4.3, we're processing Errors thrown from handler methods as well,
					// making them available for @ExceptionHandler methods and other scenarios.
					dispatchException = new NestedServletException("Handler dispatch failed", err);
				}
				processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
			}
			catch (Exception ex) {
				triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
			}
			catch (Throwable err) {
				triggerAfterCompletion(processedRequest, response, mappedHandler,
						new NestedServletException("Handler processing failed", err));
			}
			finally {
				if (asyncManager.isConcurrentHandlingStarted()) {
					// Instead of postHandle and afterCompletion
					if (mappedHandler != null) {
						mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
					}
				}
				else {
					// Clean up any resources used by a multipart request.
					if (multipartRequestParsed) {
						cleanupMultipart(processedRequest);
					}
				}
			}
		}				
	}