初识Spring MVC

spring-framework-main/README.md

 # Spring源码分析
 # Spring源码分析
 ***
 ***
-> 说明： 个人学习 Spring 源码，仅供自己学习使用，其中不以任何方式谋取利益，
-> 有需要的同学们可以自行下载。
-> 学习过程可能引用到某些博客中的信息，书籍中的信息。
-> 如果涉嫌侵权，请联系本人立即删除。
-
+> 说明： <br>
+> 个人学习 Spring 源码，仅供自己学习使用，其中不以任何方式谋取利益。<br>
+> 未对源码做任何修改，只是在学习时加入自己理解的注解（部分参照网络博客）。<br>
+> 有需要的同学们可以自行拉取。<br>
+> 学习过程可能引用到某些博客中的信息，书籍中的信息。<br>
+> 如果涉嫌侵权，请联系本人立即删除。<br>
+> 如有需要某些资源（不违反任何规定情况下）可联系我给大家分享。<br>
 
 
 `联系邮箱`：`osfung@163.com`
 `联系邮箱`：`osfung@163.com`
 
 
@@ -12,6 +14,8 @@
 
 
 源码获取方式：github 官方获取
 源码获取方式：github 官方获取
 
 
+源码地址：https://github.com/spring-projects/spring-framework
+
 Spring版本：6.0.0
 Spring版本：6.0.0
 
 
-Java版本：JDK17
+Java版本：JDK 17
\ No newline at end of file

spring-framework-main/spring-web/src/main/java/org/springframework/web/context/ContextLoader.java

@@ -257,6 +257,8 @@ public class ContextLoader {
 	 * @see #CONFIG_LOCATION_PARAM
 	 * @see #CONFIG_LOCATION_PARAM
 	 */
 	 */
 	public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
 	public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
+		// 初始化完成的 webApplicationContext 会被保存到  servletContext 的属性中，key 为 ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
+		// 所以这里是判断是否已经初始化了webApplicationContext，就抛出异常(web.xml 中声明了多次ContextLoader 的定义)，不可重复初始化。
 		if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
 		if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
 			throw new IllegalStateException(
 			throw new IllegalStateException(
 					"Cannot initialize context because there is already a root application context present - " +
 					"Cannot initialize context because there is already a root application context present - " +
@@ -289,6 +291,7 @@ public class ContextLoader {
 			}
 			}
 			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
 			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
 
 
+			// 映射当前的类加载器 与 创建的实例到全局变量 currentContextPerThread 中。
 			ClassLoader ccl = Thread.currentThread().getContextClassLoader();
 			ClassLoader ccl = Thread.currentThread().getContextClassLoader();
 			if (ccl == ContextLoader.class.getClassLoader()) {
 			if (ccl == ContextLoader.class.getClassLoader()) {
 				currentContext = this.context;
 				currentContext = this.context;
@@ -341,6 +344,7 @@ public class ContextLoader {
 	 * @see org.springframework.web.context.support.XmlWebApplicationContext
 	 * @see org.springframework.web.context.support.XmlWebApplicationContext
 	 */
 	 */
 	protected Class<?> determineContextClass(ServletContext servletContext) {
 	protected Class<?> determineContextClass(ServletContext servletContext) {
+		// 获取 contextClassName。第一次初始化自然是没有缓存的
 		String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
 		String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
 		if (contextClassName != null) {
 		if (contextClassName != null) {
 			try {
 			try {
@@ -352,6 +356,8 @@ public class ContextLoader {
 			}
 			}
 		}
 		}
 		else {
 		else {
+			// 默认策略获取 contextClassName。通过上面的静态代码块我们可以知道defaultStrategies 读取的是 ContextLoader.properties 文件中的内容
+			// 默认是 XmlWebApplicationContext
 			contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());
 			contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());
 			try {
 			try {
 				return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader());
 				return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader());

spring-framework-main/spring-web/src/main/java/org/springframework/web/context/ContextLoaderListener.java

@@ -94,6 +94,8 @@ public class ContextLoaderListener extends ContextLoader implements ServletConte
 	}
 	}
 
 
 
 
+	// 容器启动时会调用
+	// TODO: 2022/10/5 contextInitialized 在这儿
 	/**
 	/**
 	 * Initialize the root web application context.
 	 * Initialize the root web application context.
 	 */
 	 */

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

@@ -160,6 +160,7 @@ import org.springframework.web.util.WebUtils;
  * @see org.springframework.web.servlet.mvc.Controller
  * @see org.springframework.web.servlet.mvc.Controller
  * @see org.springframework.web.context.ContextLoaderListener
  * @see org.springframework.web.context.ContextLoaderListener
  */
  */
+// DispatcherServlet 在这儿，init() 方法在父类 HttpServletBean 中
 @SuppressWarnings("serial")
 @SuppressWarnings("serial")
 public class DispatcherServlet extends FrameworkServlet {
 public class DispatcherServlet extends FrameworkServlet {
 
 
@@ -492,14 +493,23 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * <p>May be overridden in subclasses in order to initialize further strategy objects.
 	 * <p>May be overridden in subclasses in order to initialize further strategy objects.
 	 */
 	 */
 	protected void initStrategies(ApplicationContext context) {
 	protected void initStrategies(ApplicationContext context) {
+		// 初始化多文件上传解析器
 		initMultipartResolver(context);
 		initMultipartResolver(context);
+		// 初始化国际化解析器
 		initLocaleResolver(context);
 		initLocaleResolver(context);
+		// 初始化主题解析器
 		initThemeResolver(context);
 		initThemeResolver(context);
+		// 初始化 HandlerMapping
 		initHandlerMappings(context);
 		initHandlerMappings(context);
+		// 初始化 HandlerAdapter
 		initHandlerAdapters(context);
 		initHandlerAdapters(context);
+		// 初始化 Handler异常解析器
 		initHandlerExceptionResolvers(context);
 		initHandlerExceptionResolvers(context);
+		// 初始化RequestToViewNameTranslator
 		initRequestToViewNameTranslator(context);
 		initRequestToViewNameTranslator(context);
+		// 初始化 视图解析器
 		initViewResolvers(context);
 		initViewResolvers(context);
+		// 初始化 FlashMapManager
 		initFlashMapManager(context);
 		initFlashMapManager(context);
 	}
 	}
 
 
@@ -509,6 +519,10 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * no multipart handling is provided.
 	 * no multipart handling is provided.
 	 */
 	 */
 	private void initMultipartResolver(ApplicationContext context) {
 	private void initMultipartResolver(ApplicationContext context) {
+		// 在 Spring 中，MultipartResolver 主要用来处理文件上传。默认情况下，Spring是没有 Multipart 处理的。
+		// 如果想使用 Spring 的 Multipart，则需要手动注入 Multipart 解析器，即MultipartResolver。
+		// 这样Spring 会检查每个请求是否包含 Multipart，如果包含，那么 MultipartResolver 就会解析它。
+		// 一般我们可以注入 CommonsMultipartResolver。
 		try {
 		try {
 			this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
 			this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
 			if (logger.isTraceEnabled()) {
 			if (logger.isTraceEnabled()) {
@@ -533,6 +547,7 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * we default to AcceptHeaderLocaleResolver.
 	 * we default to AcceptHeaderLocaleResolver.
 	 */
 	 */
 	private void initLocaleResolver(ApplicationContext context) {
 	private void initLocaleResolver(ApplicationContext context) {
+		// 一共有三种实现类，一种使用 URL 后缀类型，一种基于 cookie 实现，一种基于 session 来实现
 		try {
 		try {
 			this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class);
 			this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class);
 			if (logger.isTraceEnabled()) {
 			if (logger.isTraceEnabled()) {
@@ -558,6 +573,7 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * we default to a FixedThemeResolver.
 	 * we default to a FixedThemeResolver.
 	 */
 	 */
 	private void initThemeResolver(ApplicationContext context) {
 	private void initThemeResolver(ApplicationContext context) {
+		// 通过主题来改变用户体验，三种实现类：固定主题、主题保存在 session 中、主题保存在 cookie 中。
 		try {
 		try {
 			this.themeResolver = context.getBean(THEME_RESOLVER_BEAN_NAME, ThemeResolver.class);
 			this.themeResolver = context.getBean(THEME_RESOLVER_BEAN_NAME, ThemeResolver.class);
 			if (logger.isTraceEnabled()) {
 			if (logger.isTraceEnabled()) {
@@ -583,19 +599,24 @@ public class DispatcherServlet extends FrameworkServlet {
 	 * we default to BeanNameUrlHandlerMapping.
 	 * we default to BeanNameUrlHandlerMapping.
 	 */
 	 */
 	private void initHandlerMappings(ApplicationContext context) {
 	private void initHandlerMappings(ApplicationContext context) {
+		// 映射器可以有多个，在选用时会进行优先级排序，依次调用映射器链，找到就会直接返回处理器路径。
 		this.handlerMappings = null;
 		this.handlerMappings = null;
 
 
+		// 如果启用所有的HandlerMapping。可以通过这个参数来控制是使用指定的HandlerMapping，还是检索所有的
 		if (this.detectAllHandlerMappings) {
 		if (this.detectAllHandlerMappings) {
 			// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
 			// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
+			// 寻找所有的 HandlerMapping 类型的类
 			Map<String, HandlerMapping> matchingBeans =
 			Map<String, HandlerMapping> matchingBeans =
 					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
 					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
 			if (!matchingBeans.isEmpty()) {
 			if (!matchingBeans.isEmpty()) {
 				this.handlerMappings = new ArrayList<>(matchingBeans.values());
 				this.handlerMappings = new ArrayList<>(matchingBeans.values());
 				// We keep HandlerMappings in sorted order.
 				// We keep HandlerMappings in sorted order.
+				// 按照优先级进行排序
 				AnnotationAwareOrderComparator.sort(this.handlerMappings);
 				AnnotationAwareOrderComparator.sort(this.handlerMappings);
 			}
 			}
 		}
 		}
 		else {
 		else {
+			// 如果使用指定的参数，从容器中获取 beanName 为 "handlerMapping" 的 HandlerMapping
 			try {
 			try {
 				HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
 				HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
 				this.handlerMappings = Collections.singletonList(hm);
 				this.handlerMappings = Collections.singletonList(hm);
@@ -607,6 +628,7 @@ public class DispatcherServlet extends FrameworkServlet {
 
 
 		// Ensure we have at least one HandlerMapping, by registering
 		// Ensure we have at least one HandlerMapping, by registering
 		// a default HandlerMapping if no other mappings are found.
 		// a default HandlerMapping if no other mappings are found.
+		// 如果 handlerMappings 为null。则使用默认策略指定的HandlerMapping
 		if (this.handlerMappings == null) {
 		if (this.handlerMappings == null) {
 			this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
 			this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
 			if (logger.isTraceEnabled()) {
 			if (logger.isTraceEnabled()) {
@@ -870,8 +892,11 @@ public class DispatcherServlet extends FrameworkServlet {
 			}
 			}
 		}
 		}
 
 
+		// 获取Name
 		String key = strategyInterface.getName();
 		String key = strategyInterface.getName();
+		// 从配置文件中获取 value
 		String value = defaultStrategies.getProperty(key);
 		String value = defaultStrategies.getProperty(key);
+		// 获取到 value 之后就是对 value 的处理，添加返回。
 		if (value != null) {
 		if (value != null) {
 			String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
 			String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
 			List<T> strategies = new ArrayList<>(classNames.length);
 			List<T> strategies = new ArrayList<>(classNames.length);

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

@@ -528,7 +528,9 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 		long startTime = System.currentTimeMillis();
 		long startTime = System.currentTimeMillis();
 
 
 		try {
 		try {
+			// 委托给 initWebApplicationContext 方法来完成进一步的初始化
 			this.webApplicationContext = initWebApplicationContext();
 			this.webApplicationContext = initWebApplicationContext();
+			// 留给子类覆盖操作
 			initFrameworkServlet();
 			initFrameworkServlet();
 		}
 		}
 		catch (ServletException | RuntimeException ex) {
 		catch (ServletException | RuntimeException ex) {
@@ -563,6 +565,7 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
 				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
 		WebApplicationContext wac = null;
 		WebApplicationContext wac = null;
 
 
+		// 1. 如果 webApplicationContext 在构造函数的时候被注入，则 wac != null, 则可以直接使用
 		if (this.webApplicationContext != null) {
 		if (this.webApplicationContext != null) {
 			// A context instance was injected at construction time -> use it
 			// A context instance was injected at construction time -> use it
 			wac = this.webApplicationContext;
 			wac = this.webApplicationContext;
@@ -574,9 +577,11 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 					// the root application context (if any; may be null) as the parent
 					// the root application context (if any; may be null) as the parent
 					cwac.setParent(rootContext);
 					cwac.setParent(rootContext);
 				}
 				}
+				// 2.刷新上下文环境
 				configureAndRefreshWebApplicationContext(cwac);
 				configureAndRefreshWebApplicationContext(cwac);
 			}
 			}
 		}
 		}
+		// 3. 如果构造函数并没有注入，则wac为null，根据 contextAttribute 属性加载 WebApplicationContext
 		if (wac == null) {
 		if (wac == null) {
 			// No context instance was injected at construction time -> see if one
 			// No context instance was injected at construction time -> see if one
 			// has been registered in the servlet context. If one exists, it is assumed
 			// has been registered in the servlet context. If one exists, it is assumed
@@ -584,8 +589,10 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 			// user has performed any initialization such as setting the context id
 			// user has performed any initialization such as setting the context id
 			wac = findWebApplicationContext();
 			wac = findWebApplicationContext();
 		}
 		}
+		// 4. 如果上面两个方式都没有加载到 WebApplicationContext，则尝试自己加载
 		if (wac == null) {
 		if (wac == null) {
 			// No context instance is defined for this servlet -> create a local one
 			// No context instance is defined for this servlet -> create a local one
+			// 自己尝试创建WebApplicationContext
 			wac = createWebApplicationContext(rootContext);
 			wac = createWebApplicationContext(rootContext);
 		}
 		}
 
 
@@ -594,6 +601,7 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 			// support or the context injected at construction time had already been
 			// support or the context injected at construction time had already been
 			// refreshed -> trigger initial onRefresh manually here.
 			// refreshed -> trigger initial onRefresh manually here.
 			synchronized (this.onRefreshMonitor) {
 			synchronized (this.onRefreshMonitor) {
+				// 5.刷新
 				onRefresh(wac);
 				onRefresh(wac);
 			}
 			}
 		}
 		}
@@ -659,15 +667,18 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 
 
 		wac.setEnvironment(getEnvironment());
 		wac.setEnvironment(getEnvironment());
 		wac.setParent(parent);
 		wac.setParent(parent);
+		// 获取web.xml 配置的 DispatcherServlet init-params contextConfigLocation 属性
 		String configLocation = getContextConfigLocation();
 		String configLocation = getContextConfigLocation();
 		if (configLocation != null) {
 		if (configLocation != null) {
 			wac.setConfigLocation(configLocation);
 			wac.setConfigLocation(configLocation);
 		}
 		}
+		// 配置 WebApplicationContext 实例并刷新
 		configureAndRefreshWebApplicationContext(wac);
 		configureAndRefreshWebApplicationContext(wac);
 
 
 		return wac;
 		return wac;
 	}
 	}
 
 
+	// 已经创建的 WebApplicationContext 实例进行配置及刷新。其实就是配置并刷新Spring。
 	protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
 	protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
 		if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
 		if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
 			// The application context id is still set to its original default value
 			// The application context id is still set to its original default value
@@ -682,6 +693,7 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 			}
 			}
 		}
 		}
 
 
+		// 设置一些属性，ServletContext、ServletConfig等
 		wac.setServletContext(getServletContext());
 		wac.setServletContext(getServletContext());
 		wac.setServletConfig(getServletConfig());
 		wac.setServletConfig(getServletConfig());
 		wac.setNamespace(getNamespace());
 		wac.setNamespace(getNamespace());

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

@@ -148,12 +148,16 @@ public abstract class HttpServletBean extends HttpServlet implements Environment
 	public final void init() throws ServletException {
 	public final void init() throws ServletException {
 
 
 		// Set bean properties from init parameters.
 		// Set bean properties from init parameters.
+		// 1. 封装及验证初始化参数
 		PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
 		PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
 		if (!pvs.isEmpty()) {
 		if (!pvs.isEmpty()) {
 			try {
 			try {
+				// 2. 将当前 Servlet 实例转化为 BeanWrapper 实例
 				BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
 				BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
+				// 3. 注册于相对于 Resource 的属性编辑器
 				ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
 				ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
 				bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
 				bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
+				// 4. 属性注入（支持 Spring 的自动注入）
 				initBeanWrapper(bw);
 				initBeanWrapper(bw);
 				bw.setPropertyValues(pvs, true);
 				bw.setPropertyValues(pvs, true);
 			}
 			}
@@ -166,6 +170,7 @@ public abstract class HttpServletBean extends HttpServlet implements Environment
 		}
 		}
 
 
 		// Let subclasses do whatever initialization they like.
 		// Let subclasses do whatever initialization they like.
+		// 5. servletBean的初始化
 		initServletBean();
 		initServletBean();
 	}
 	}
 
 
@@ -220,10 +225,12 @@ public abstract class HttpServletBean extends HttpServlet implements Environment
 			Set<String> missingProps = (!CollectionUtils.isEmpty(requiredProperties) ?
 			Set<String> missingProps = (!CollectionUtils.isEmpty(requiredProperties) ?
 					new HashSet<>(requiredProperties) : null);
 					new HashSet<>(requiredProperties) : null);
 
 
+			// 获取 web.xml 中 DispatcherServlet 配置的 init-params 属性内容
 			Enumeration<String> paramNames = config.getInitParameterNames();
 			Enumeration<String> paramNames = config.getInitParameterNames();
 			while (paramNames.hasMoreElements()) {
 			while (paramNames.hasMoreElements()) {
 				String property = paramNames.nextElement();
 				String property = paramNames.nextElement();
 				Object value = config.getInitParameter(property);
 				Object value = config.getInitParameter(property);
+				// 保存 init-params 属性
 				addPropertyValue(new PropertyValue(property, value));
 				addPropertyValue(new PropertyValue(property, value));
 				if (missingProps != null) {
 				if (missingProps != null) {
 					missingProps.remove(property);
 					missingProps.remove(property);