给昨天补一个push，今天继续加油

spring-framework-main/spring-web/src/main/java/org/springframework/web/method/support/HandlerMethodReturnValueHandlerComposite.java

@@ -71,20 +71,26 @@ public class HandlerMethodReturnValueHandlerComposite implements HandlerMethodRe
 	public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
 			ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
 
+		// 查找处理器
 		HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);
 		if (handler == null) {
 			throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
 		}
+		// 此处handler就是HandlerMethodReturnValueHandler的实现类
+		// HandlerMethodReturnValueHandler#handleReturnValue处理返回值
 		handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
 	}
 
 	@Nullable
 	private HandlerMethodReturnValueHandler selectHandler(@Nullable Object value, MethodParameter returnType) {
 		boolean isAsyncValue = isAsyncReturnValue(value, returnType);
+		// returnValueHandlers就是HandlerMethodReturnValueHandler的实现类集合，默认有15个实现类
+		// 注意：returnValueHandlers是有顺序的
 		for (HandlerMethodReturnValueHandler handler : this.returnValueHandlers) {
 			if (isAsyncValue && !(handler instanceof AsyncHandlerMethodReturnValueHandler)) {
 				continue;
 			}
+			// 使用supportsReturnType方法判断该处理器是否支持解析当前返回值
 			if (handler.supportsReturnType(returnType)) {
 				return handler;
 			}

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/DispatcherServlet.java

@@ -1322,7 +1322,9 @@ public class DispatcherServlet extends FrameworkServlet {
 	@Nullable
 	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
 		if (this.handlerMappings != null) {
+			// 这里的 HandlerMapping 如果没有特殊操作，则默认是从配置文件中读取并加载的 HandlerMapping
 			for (HandlerMapping mapping : this.handlerMappings) {
+				// 调用HandlerMapping 的getHandler 方法。
 				HandlerExecutionChain handler = mapping.getHandler(request);
 				if (handler != null) {
 					return handler;

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractDetectingUrlHandlerMapping.java

@@ -75,9 +75,11 @@ public abstract class AbstractDetectingUrlHandlerMapping extends AbstractUrlHand
 
 		// Take any bean name that we can determine URLs for.
 		for (String beanName : beanNames) {
+			// 记录开头是 "/" 的 bean
 			String[] urls = determineUrlsForHandler(beanName);
 			if (!ObjectUtils.isEmpty(urls)) {
 				// URL paths found: Let's consider it a handler.
+				// 注册成handler
 				registerHandler(urls, beanName);
 			}
 		}

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractHandlerMapping.java

@@ -495,7 +495,9 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	@Override
 	@Nullable
 	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
+		// 1. 调用 getHandlerInternal 获取 handler。该方法供子类实现。
 		Object handler = getHandlerInternal(request);
+		// 如果没有获取到 handler。则获取默认的handler
 		if (handler == null) {
 			handler = getDefaultHandler();
 		}
@@ -503,6 +505,7 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 			return null;
 		}
 		// Bean name or resolved handler?
+		// 如果 handler  是 String类型，则会认为是 beanName。从Spring容器中获取 bean实例
 		if (handler instanceof String handlerName) {
 			handler = obtainApplicationContext().getBean(handlerName);
 		}
@@ -512,6 +515,7 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 			initLookupPath(request);
 		}
 
+		// 2. 生成拦截器链路
 		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
 
 		if (logger.isTraceEnabled()) {
@@ -600,9 +604,11 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 	 * @see #getAdaptedInterceptors()
 	 */
 	protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
+		// 构建一个执行链
 		HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain handlerExecutionChain ?
 				handlerExecutionChain : new HandlerExecutionChain(handler));
 
+		// 遍历所有的拦截器，如果拦截器匹配符则加入到执行链中。adaptedInterceptors 是在 Mapping 初始化的时候加载的
 		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
 			if (interceptor instanceof MappedInterceptor mappedInterceptor) {
 				if (mappedInterceptor.matches(request)) {

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractHandlerMethodMapping.java

@@ -40,6 +40,7 @@ import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.MethodIntrospector;
 import org.springframework.lang.Nullable;
+import org.springframework.stereotype.Service;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.LinkedMultiValueMap;
@@ -220,11 +221,15 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 	 * @see #handlerMethodsInitialized
 	 */
 	protected void initHandlerMethods() {
+		// getCandidateBeanNames(): 从 Spring 容器中获取所有候选的beanName。
 		for (String beanName : getCandidateBeanNames()) {
+			// 如果beanName 不是以 SCOPED_TARGET_NAME_PREFIX 开头，则进行处理
 			if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
+				// 1. 初始 候选的beanName
 				processCandidateBean(beanName);
 			}
 		}
+		// 这里就是打印了一下log日志
 		handlerMethodsInitialized(getHandlerMethods());
 	}
 
@@ -262,7 +267,9 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 				logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
 			}
 		}
+		// 有 @controller 修饰或有 @RequestMapping修饰
 		if (beanType != null && isHandler(beanType)) {
+			// 筛选出合适的 HandlerMethod 注册
 			detectHandlerMethods(beanName);
 		}
 	}
@@ -273,14 +280,19 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 	 * @see #getMappingForMethod
 	 */
 	protected void detectHandlerMethods(Object handler) {
+		// 获取 handlerType。这里传入的 handler如果是  String 就是 beanName，从上下文中获取type，否则就直接认为是 Handler
 		Class<?> handlerType = (handler instanceof String beanName ?
 				obtainApplicationContext().getType(beanName) : handler.getClass());
 
 		if (handlerType != null) {
+			// 返回给定类的用户定义类：通常只是给定的类，但对于CGLIB生成的子类，则返回原始类
 			Class<?> userType = ClassUtils.getUserClass(handlerType);
+			// 遍历当前bean的所有方法，筛选出合适的 handler 方法 以及 注解信息
+			// 这里需要注意的是 MethodIntrospector.selectMethods 底层将 getMappingForMethod 返回为 null 的值给过滤掉了
 			Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
 					(MethodIntrospector.MetadataLookup<T>) method -> {
 						try {
+							// 供子类实现
 							return getMappingForMethod(method, userType);
 						}
 						catch (Throwable ex) {
@@ -294,8 +306,11 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 			else if (mappingsLogger.isDebugEnabled()) {
 				mappingsLogger.debug(formatMappings(userType, methods));
 			}
+			// 遍历所有的 methods(这里的 methods 经过上面的筛选后，都是被 @RequestMapping 注解修饰的方法)
 			methods.forEach((method, mapping) -> {
+				// 这里是针对 cglib 代理特殊处理
 				Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
+				//注册 HandlerMethod
 				registerHandlerMethod(handler, invocableMethod, mapping);
 			});
 		}
@@ -377,9 +392,11 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 	@Override
 	@Nullable
 	protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
+		// 从 request 中解析出 请求路径
 		String lookupPath = initLookupPath(request);
 		this.mappingRegistry.acquireReadLock();
 		try {
+			// 查找 HandlerMethod
 			HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
 			return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
 		}
@@ -399,16 +416,25 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 	 */
 	@Nullable
 	protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
+		// 通过 url 获取匹配路径
+		// springMVC 会在初始化的时候建立 URL 和相应 RequestMappingInfo 的映射，这点在上面的解析中我们可以知道。
+		// 如果不是restful接口，这里就可以直接获取到。
+		// 这里是通过 urlLookup 获取的 RequestMappingInfo
 		List<Match> matches = new ArrayList<>();
 		List<T> directPathMatches = this.mappingRegistry.getMappingsByDirectPath(lookupPath);
 		if (directPathMatches != null) {
+			// 将匹配的 Mapping 保存到 matches 中。
 			addMatchingMappings(directPathMatches, matches, request);
 		}
+		// 如果上面没有获取到匹配的路径，则只能遍历所有的 mapping。
+		// 由于会遍历所有的 RequestMapping。所以性能会随着 RequestMapping 数量的增加降低
 		if (matches.isEmpty()) {
 			addMatchingMappings(this.mappingRegistry.getRegistrations().keySet(), matches, request);
 		}
+		// 如果 matches 不为空，则说明有匹配的 Mapping
 		if (!matches.isEmpty()) {
 			Match bestMatch = matches.get(0);
+			// 如果合适的 Mapping 不止一个，则筛选出最合适的
 			if (matches.size() > 1) {
 				Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
 				matches.sort(comparator);
@@ -628,28 +654,40 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 		}
 
 		public void register(T mapping, Object handler, Method method) {
+			// 加写锁
 			this.readWriteLock.writeLock().lock();
 			try {
+				// 将 handler 和 method 封装成一个 HandlerMethod 实例
 				HandlerMethod handlerMethod = createHandlerMethod(handler, method);
+				// 校验实例的合法性。即唯一性
 				validateMethodMapping(handlerMethod, mapping);
 
+				// 获取url映射，如果是 restful 请求则获取不到。建立 url 和Mapping 的映射。
+				// 一个mapping 可以对应多个url
 				Set<String> directPaths = AbstractHandlerMethodMapping.this.getDirectPaths(mapping);
+				// 这里将url 和  mapping映射起来
+				// 在进行匹配的时候，就是先根据url找到合适的mapping，然后根据找到的mapping再去找到HandlerMethod
 				for (String path : directPaths) {
 					this.pathLookup.add(path, mapping);
 				}
 
+				// 保存 类名#方法名 ： HandlerMethod 的映射关系
 				String name = null;
 				if (getNamingStrategy() != null) {
+					// 这里解析出来的 name 并不是完整的类名，而是类名的首字母组合。比如方法名是 DemoController.say()，
+					// 解析出来的name即为 DC#say。如果是 SayController.say()。解析出来则为 name = SC#say
 					name = getNamingStrategy().getName(handlerMethod, mapping);
 					addMappingName(name, handlerMethod);
 				}
 
+				// @CrossOrigin 跨域注解请求的初始化配置
 				CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
 				if (corsConfig != null) {
 					corsConfig.validateAllowCredentials();
 					this.corsLookup.put(handlerMethod, corsConfig);
 				}
 
+				// 保存到 registry 中
 				this.registry.put(mapping,
 						new MappingRegistration<>(mapping, handlerMethod, directPaths, name, corsConfig != null));
 			}

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractUrlHandlerMapping.java

@@ -409,6 +409,7 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping i
 		Object resolvedHandler = handler;
 
 		// Eagerly resolve handler if referencing singleton via name.
+		// 如果不是懒加载 && handler 是 String 类型。
 		if (!this.lazyInitHandlers && handler instanceof String handlerName) {
 			ApplicationContext applicationContext = obtainApplicationContext();
 			if (applicationContext.isSingleton(handlerName)) {
@@ -416,6 +417,7 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping i
 			}
 		}
 
+		// 判断 handlerMap 中已经保存了该 url
 		Object mappedHandler = this.handlerMap.get(urlPath);
 		if (mappedHandler != null) {
 			if (mappedHandler != resolvedHandler) {
@@ -425,12 +427,14 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping i
 			}
 		}
 		else {
+			// 如果是 urlPath 是 "/" 开头。则设置为根处理器
 			if (urlPath.equals("/")) {
 				if (logger.isTraceEnabled()) {
 					logger.trace("Root mapping to " + getHandlerDescription(handler));
 				}
 				setRootHandler(resolvedHandler);
 			}
+			// 如果是 urlPath 是 "/*" 开头。则设置为 默认处理器
 			else if (urlPath.equals("/*")) {
 				if (logger.isTraceEnabled()) {
 					logger.trace("Default mapping to " + getHandlerDescription(handler));
@@ -438,6 +442,7 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping i
 				setDefaultHandler(resolvedHandler);
 			}
 			else {
+				// 否则的话，保存到 handlerMap 中
 				this.handlerMap.put(urlPath, resolvedHandler);
 				if (getPatternParser() != null) {
 					this.pathPatternHandlerMap.put(getPatternParser().parse(urlPath), resolvedHandler);

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerMapping.java

@@ -187,6 +187,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 	@Override
 	@SuppressWarnings("deprecation")
 	public void afterPropertiesSet() {
+		// 进行 RequestMapping 的配置
 		this.config = new RequestMappingInfo.BuilderConfiguration();
 		this.config.setTrailingSlashMatch(useTrailingSlashMatch());
 		this.config.setContentNegotiationManager(getContentNegotiationManager());
@@ -202,6 +203,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 			this.config.setPathMatcher(getPathMatcher());
 		}
 
+		// 调用父类的  afterPropertiesSet 方法。
 		super.afterPropertiesSet();
 	}
 
@@ -279,12 +281,17 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 	@Override
 	@Nullable
 	protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
+		// 转换成 RequestMappingInfo，如果方法没有被 @RequestMapping 注解修饰，则会返回null
+		// 解析出来 方法 上 @RequestMapping 注解的各种信息
 		RequestMappingInfo info = createRequestMappingInfo(method);
 		if (info != null) {
+			// 解析出来 bean 上 @RequestMapping 注解的各种信息
 			RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
 			if (typeInfo != null) {
+				// 合并类和方法的 @RequestMapping 注解信息
 				info = typeInfo.combine(info);
 			}
+			// 获取前缀，拼接前缀
 			String prefix = getPathPrefix(handlerType);
 			if (prefix != null) {
 				info = RequestMappingInfo.paths(prefix).options(this.config).build().combine(info);
@@ -316,9 +323,12 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 	 */
 	@Nullable
 	private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
+		// 获取当前方法上的 @RequestMapping 注解
 		RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
+		// 获取自定义的方法条件
 		RequestCondition<?> condition = (element instanceof Class ?
 				getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
+		// 这里可以看到: 如果 requestMapping = null，则会直接返回 null，否则会封装成一个 RequestMappingInfo (包含 @RequestMapping 注解的各种参数) 返回。
 		return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
 	}
 
@@ -420,6 +430,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 	}
 
 	private void updateConsumesCondition(RequestMappingInfo info, Method method) {
+		// 对 @RequestBody 注解进行了进一步解析
 		ConsumesRequestCondition condition = info.getConsumesCondition();
 		if (!condition.isEmpty()) {
 			for (Parameter parameter : method.getParameters()) {

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ServletInvocableHandlerMethod.java

@@ -114,6 +114,7 @@ public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {
 	public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
 			Object... providedArgs) throws Exception {
 
+		// 调用handler（controller+method），得到返回值
 		Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
 		setResponseStatus(webRequest);
 
@@ -132,6 +133,8 @@ public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {
 		mavContainer.setRequestHandled(false);
 		Assert.state(this.returnValueHandlers != null, "No return value handlers");
 		try {
+			// 处理返回值方法
+			// returnValueHandlers是HandlerMethodReturnValueHandlerComposite类
 			this.returnValueHandlers.handleReturnValue(
 					returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
 		}

spring-framework-main/spring-webmvc/src/main/java/org/springframework/web/servlet/view/AbstractView.java

@@ -18,12 +18,7 @@ package org.springframework.web.servlet.view;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.Properties;
-import java.util.Set;
-import java.util.StringTokenizer;
+import java.util.*;
 
 import jakarta.servlet.ServletOutputStream;
 import jakarta.servlet.http.HttpServletRequest;