Spring 源码解析一:SpringMVC 的加载机制
1. spring-framework
蕴含的模块
在解析 SpringMVC
的加载机制之前,先来看看官网 spring-framework
蕴含有哪些模块,各有什么用。
spring-framework 官网仓库
spring-jcl
:spring
框架的通用日志解决spring-core
:spring
框架的外围机制模块,包含 Java 字节码的操作解决与动静生成、依赖注入机制(也叫管制反转)、工具类库、
注解操作、编码解决与数据转换、资源加载与解决、环境加载机制等spring-beans
:spring bean
的定义、加载、解析、编辑等spring-context
:spring
框架的上下文环境,包含利用缓存、利用事件、利用配置、外围注解定义与解决、资源加载、异步与定时工作、数据验证与格式化等spring-aop
:面向切面编程的封装与解决spring-aspects
:应用 AspectJ 作为底层实现的面向切面编程spring-tx
:事务的封装与解决spring-jdbc
:数据库链接的封装与解决spring-context-indexer
:对注解@Indexed
的反对spring-context-support
:对一些第三方库的可选反对,如ehcache, javamail, quartz, freemarker
spring-oxm
:对 O/X Mapper 的封装spring-messaging
:对http, rsocket, simp
等消息传递协定的封装spring-jms
:对 JMS(Java 音讯服务) 的封装spring-expression
:Spring Expression Language (SpEL) Spring 表达式语言的实现spring-r2dbc
:对 R2DBC 的封装spring-orm
:对 JPA 和 hibernate 的封装spring-web
:提供了 Web 框架的根底构造与技术,如 Http 的调用、过滤、解决等spring-webmvc
:Web MVC 架构的实现,包含 Servlet 容器初始化、路由映射、视图渲染、响应解决等spring-websocket
:对 WebSocket 的反对spring-webflux
:Reactive Web 框架的实现,与spring-webmvc
绝对
SpringMVC 框架的外围模块次要是:spring-core
、spring-beans
、spring-context
、spring-web
、spring-webmvc
,前面也次要从这几个模块来剖析。
1.1. spring-core
spring-core
的外围性能有几点须要在这里简略介绍一下:
spring-core
有弱小的 Java 字节码操作解决性能与动静生成性能,这是面向切面编程、数据类型转换、SpEL 表达式等性能的根底spring-core
提供了依赖注入机制,这是spring bean
加载的根底,也是咱们能够应用@Autowired
主动装载对象等性能的底层机制spring-core
提供了环境加载的机制,所以咱们能够应用application-dev.yml, application-test.yml, application-prod.yml, ...
来依据环境加载不同的配置spring-core
提供了一个相似 Java SPI 的的扩大机制,能够主动实例化其余包指定的类,spring-boot, spring-cloud
都依赖这个机制主动加载资源。
在META-INF/spring.factories
文件中定义须要主动加载的类,具体介绍能够参考 Spring Factories
1.2. spring-beans
Spring bean 的加载与扩大机制有几点须要在这里简略介绍一下:
- Spring bean 的定义次要是两种:基于注解的定义、基于 XML 文件的定义
spring-beans
提供了基于 XML 配置的、第三方对 bean 的自定义扩大机制,次要是在META-INF/spring.handlers, META-INF/spring.schemas
文件中定义须要扩大的标签,比方<dubbo:application name="name"/>, <dubbo:registry address="address"/>
- 基于注解的自定义扩大,须要依赖
spring-boot
的扩大加载机制
1.3. spring-context
spring-context
是利用的外围解决局部,包含:
- 利用缓存
- 利用事件
- 利用配置
- 外围注解定义与解决
- 资源加载
- 异步与定时工作
- 数据验证与格式化
等,@ComponentScan, @Profile, @Conditional, @Bean, @Async, @Controller, @Service, @Component, @Validated
等这类框架外围注解便是在这里定义的。
1.4. spring-web
spring-web
是 Http 的外围解决局部,次要蕴含:
- 外围 Http 申请与响应解决(包含 Cookie、缓存、多媒体等)
- Http 申请与响应编解码与转换(包含 Json、XML、ProtoBuf 等)
- Reactive Web 框架根底解决
- 调用客户端(如
RestTemplate
) - Servlet 上下文环境
- 申请过滤器
- Multipart 文件上传解决
等,@RequestMapping, @RequestParam, @PathVariable, @ResponseBody, @RestController
等这类 Web 外围注解便是在这里定义的。
1.5. spring-webmvc
spring-webmvc
依赖于 spring-web
,次要性能包含:
- Servlet 容器初始化
- 路由映射
- 视图渲染
- 响应解决
等,如果不应用 Spring MVC ,但想要借助其它 Spring 反对的 web 相干技术的劣势,那么只需依赖 spring-web
,如 spring-webflux
。
1.6. spring-webflux
spring-webflux
与 spring-webmvc
绝对应,webmvc
是同步阻塞框架,而 webflux
是异步非阻塞框架,是 Spring Framework 5.0 中引入的新的响应式 web 框架。
参考:Spring WebFlux 入门、Spring WebFlux :: Spring Docs
2. 一个简略的 spring-webmvc
我的项目配置
在 WEB-INF/web.xml
文件中如下配置:
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <display-name>springMVC</display-name> <!-- 部署 DispatcherServlet --> <servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:springmvc-servlet.xml</param-value> </init-param> <!-- 容器再启动时立刻加载servlet --> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>springmvc</servlet-name> <!-- 解决所有URL --> <url-pattern>/</url-pattern> </servlet-mapping> <!-- 定义应用程序监听器 --> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener></web-app>
这里有两个入口类:
servlet-class
org.springframework.web.servlet.DispatcherServlet: 指定用来解决对应 URL 申请的类listener-class
org.springframework.web.context.ContextLoaderListener: 设置事件监听器,事件监听程序在建设、批改和删除会话或 servlet 环境时失去告诉
这两个类别离定义在 spring-webmvc
与 spring-web
中,上面对他们一一进行解析。
3. DispatcherServlet
先来看看 DispatcherServlet
的继承关系:
- javax.servlet.Servlet - javax.servlet.GenericServlet - javax.servlet.http.HttpServlet - HttpServletBean - FrameworkServlet - DispatcherServlet
3.1. javax.servlet.Servlet
首先看看 javax.servlet.Servlet
javax.servlet.Servlet
次要定义了 2 个办法:
init
:初始化 Servlet,只执行一次service
:响应申请,每次 http 申请都会调用这个办法
public interface Servlet { // 初始化 Servlet,只执行一次 public void init(ServletConfig config) throws ServletException; // 响应申请,每次http申请都会调用这个办法 public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException; // 销毁 Servlet public void destroy();}
3.2. javax.servlet.GenericServlet
再来看看 javax.servlet.GenericServlet
javax.servlet.GenericServlet
次要是重载了 init
办法
public abstract class GenericServlet implements Servlet, ServletConfig, java.io.Serializable { public GenericServlet() {} // 增加配置初始化 public void init(ServletConfig config) throws ServletException { this.config = config; this.init(); } // 保留无参初始化 public void init() throws ServletException {} // 留给子类实现 public abstract void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;}
3.3. javax.servlet.http.HttpServlet
再来看看 javax.servlet.http.HttpServlet
javax.servlet.http.HttpServlet
次要是重载了 service
办法,并扩大了 7 个办法:
doGet
:解决 GET 申请,只输出错误信息,未实现doHead
:解决 HEAD 申请,只输出错误信息,未实现doPost
:解决 POST 申请,只输出错误信息,未实现doPut
:解决 PUT 申请,只输出错误信息,未实现doDelete
:解决 DELETE 申请,只输出错误信息,未实现doOptions
:解决 OPTIONS 申请doTrace
:解决 TRACE 申请
public abstract class HttpServlet extends GenericServlet { private static final String METHOD_DELETE = "DELETE"; private static final String METHOD_HEAD = "HEAD"; private static final String METHOD_GET = "GET"; private static final String METHOD_OPTIONS = "OPTIONS"; private static final String METHOD_POST = "POST"; private static final String METHOD_PUT = "PUT"; private static final String METHOD_TRACE = "TRACE"; protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String protocol = req.getProtocol(); String msg = lStrings.getString("http.method_get_not_supported"); if (protocol.endsWith("1.1")) { resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg); } else { resp.sendError(HttpServletResponse.SC_BAD_REQUEST, msg); } } protected void doHead(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { NoBodyResponse response = new NoBodyResponse(resp); // 调用 doGet,但body设为空body doGet(req, response); response.setContentLength(); } protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // ... 代码省略 } protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // ... 代码省略 } protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // ... 代码省略 } protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // ... 代码省略 } protected void doTrace(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // ... 代码省略 } // 实现了GET, HEAD, POST PUT, DELETE, OPTIONS, TRACE七个Http办法 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String method = req.getMethod(); if (method.equals(METHOD_GET)) { // ... 代码省略 doGet(req, resp); // ... 代码省略 } else if (method.equals(METHOD_HEAD)) { long lastModified = getLastModified(req); maybeSetLastModified(resp, lastModified); doHead(req, resp); } else if (method.equals(METHOD_POST)) { doPost(req, resp); } else if (method.equals(METHOD_PUT)) { doPut(req, resp); } else if (method.equals(METHOD_DELETE)) { doDelete(req, resp); } else if (method.equals(METHOD_OPTIONS)) { doOptions(req,resp); } else if (method.equals(METHOD_TRACE)) { doTrace(req,resp); } else { String errMsg = lStrings.getString("http.method_not_implemented"); Object[] errArgs = new Object[1]; errArgs[0] = method; errMsg = MessageFormat.format(errMsg, errArgs); resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg); } } // 把 Servlet 转化为 HttpServlet @Override public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException { HttpServletRequest request; HttpServletResponse response; if (!(req instanceof HttpServletRequest && res instanceof HttpServletResponse)) { throw new ServletException("non-HTTP request or response"); } request = (HttpServletRequest) req; response = (HttpServletResponse) res; service(request, response); }}
3.4. HttpServletBean
再来看看 HttpServletBean
HttpServletBean
次要是重载了 init
办法,并扩大了 2 个办法:
initBeanWrapper
:初始化由 Servlet Config 定义的 Java Bean,由子类实现,默认不实现initServletBean
:初始化 Servlet bean,由子类实现
public abstract class HttpServletBean extends HttpServlet implements EnvironmentCapable, EnvironmentAware { // 初始化 @Override public final void init() throws ServletException { // Set bean properties from init parameters. PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties); if (!pvs.isEmpty()) { try { BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this); ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext()); bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment())); initBeanWrapper(bw); bw.setPropertyValues(pvs, true); } catch (BeansException ex) { if (logger.isErrorEnabled()) { logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex); } throw ex; } } // Let subclasses do whatever initialization they like. initServletBean(); } // 初始化由Servlet Config定义的Java Bean,由子类实现,默认不实现 protected void initBeanWrapper(BeanWrapper bw) throws BeansException { } // 初始化Servlet bean,由子类实现 protected void initServletBean() throws ServletException { }}
3.5. FrameworkServlet
再来看看 FrameworkServlet
FrameworkServlet
是框架的外围 Servlet,次要是重载了 initServletBean
办法,并扩大了 2 个办法:
initFrameworkServlet
:初始化框架 Servlet,由子类实现,默认不实现onRefresh
:刷新上下文数据,由子类实现
重载了 service, doGet, doPost, doPut, doDelete, doOptions, doTrace
办法,并扩大了 1 个办法:
doService
:解决响应申请
3.5.1. FrameworkServlet.initServletBean
父类 HttpServletBean
初始化后,留下两个钩子 initBeanWrapper, initServletBean
,initBeanWrapper
默认并不实现,所以来看看 initServletBean
钩子的实现:FrameworkServlet.initServletBean
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { @Override protected final void initServletBean() throws ServletException { // ... 代码省略 try { // 初始化Web利用上下文 this.webApplicationContext = initWebApplicationContext(); // 初始化Web框架Servlet initFrameworkServlet(); } catch (ServletException | RuntimeException ex) { logger.error("Context initialization failed", ex); throw ex; } // ... 代码省略 } // 初始化框架Servlet,由子类实现,默认不实现 protected void initFrameworkServlet() throws ServletException {}}
再来看看 FrameworkServlet.initWebApplicationContext
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { protected WebApplicationContext initWebApplicationContext() { // 获取利用根上下文 WebApplicationContext rootContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext()); WebApplicationContext wac = null; if (this.webApplicationContext != null) { // A context instance was injected at construction time -> use it wac = this.webApplicationContext; if (wac instanceof ConfigurableWebApplicationContext) { ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac; // 未激活 if (!cwac.isActive()) { if (cwac.getParent() == null) { cwac.setParent(rootContext); } // 配置并刷新利用上下文 configureAndRefreshWebApplicationContext(cwac); } } } if (wac == null) { // 如果没有,则在ServletContext中查找是否注册过 wac = findWebApplicationContext(); } if (wac == null) { // 如果任然没有,则以rootContext为父上下文创立一个新的上下文 // 并调用 configureAndRefreshWebApplicationContext(cwac) 配置并刷新新的上下文 // 默认应用 XmlWebApplicationContext(基于XML加载)作为利用上下文 wac = createWebApplicationContext(rootContext); } if (!this.refreshEventReceived) { // 重载上下文数据 synchronized (this.onRefreshMonitor) { onRefresh(wac); } } if (this.publishContext) { // 把上下文注册到ServletContext中 String attrName = getServletContextAttributeName(); getServletContext().setAttribute(attrName, wac); } return wac; } // 以parent为父上下文创立一个新的上下文 // 并调用 configureAndRefreshWebApplicationContext(cwac) 配置并刷新新的上下文 // 默认应用 XmlWebApplicationContext(基于XML加载)作为利用上下文 protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) { // 这里默认应用 XmlWebApplicationContext(基于XML加载) Class<?> contextClass = getContextClass(); ConfigurableWebApplicationContext wac = (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); wac.setEnvironment(getEnvironment()); wac.setParent(parent); String configLocation = getContextConfigLocation(); if (configLocation != null) { wac.setConfigLocation(configLocation); } configureAndRefreshWebApplicationContext(wac); return wac; }}
这其中有两个办法须要深刻解析:configureAndRefreshWebApplicationContext
, onRefresh
再来看看 FrameworkServlet.configureAndRefreshWebApplicationContext
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) { // ... 代码省略 // 设置ServletContext wac.setServletContext(getServletContext()); // 设置ServletConfig wac.setServletConfig(getServletConfig()); wac.setNamespace(getNamespace()); // 增加利用事件监听器,利用事件会触发以后对象的onApplicationEvent办法 // 进一步,会调用以后对象的onRefresh办法,刷新上下文数据 wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener())); // ... 代码省略 // 初始化一些须要初始加载的类,调用这些类的initialize办法 applyInitializers(wac); // 利用上下文刷新 wac.refresh(); } // 利用事件会触发此办法,而后调用以后对象的onRefresh办法,刷新上下文数据 public void onApplicationEvent(ContextRefreshedEvent event) { this.refreshEventReceived = true; synchronized (this.onRefreshMonitor) { onRefresh(event.getApplicationContext()); } }}
再来看看 FrameworkServlet.onRefresh
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { protected void onRefresh(ApplicationContext context) { // 由子类来实现 }}
3.5.2. FrameworkServlet.service
再来看看 FrameworkServlet.service
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpMethod httpMethod = HttpMethod.resolve(request.getMethod()); // 如果Http办法是Patch或没有,扩大解决 if (httpMethod == HttpMethod.PATCH || httpMethod == null) { processRequest(request, response); } else { super.service(request, response); } } @Override protected final void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 扩大解决 processRequest(request, response); } @Override protected final void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 扩大解决 processRequest(request, response); } @Override protected final void doPut(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 扩大解决 processRequest(request, response); } @Override protected final void doDelete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 扩大解决 processRequest(request, response); } @Override protected void doOptions(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (this.dispatchOptionsRequest || CorsUtils.isPreFlightRequest(request)) { // 扩大解决 processRequest(request, response); if (response.containsHeader("Allow")) { // Proper OPTIONS response coming from a handler - we're done. return; } } // ... 代码省略 } @Override protected void doTrace(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (this.dispatchTraceRequest) { // 扩大解决 processRequest(request, response); if ("message/http".equals(response.getContentType())) { // Proper TRACE response coming from a handler - we're done. return; } } super.doTrace(request, response); }}
再来看看扩大解决办法 FrameworkServlet.processRequest
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware { protected final void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // ... 代码省略 // 记录申请属性与上下文环境,申请解决完后派发事件 LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext(); LocaleContext localeContext = buildLocaleContext(request); RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes(); ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes); WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor()); initContextHolders(request, localeContext, requestAttributes); try { doService(request, response); } // ... 代码省略 finally { resetContextHolders(request, previousLocaleContext, previousAttributes); if (requestAttributes != null) { requestAttributes.requestCompleted(); } logResult(request, response, failureCause, asyncManager); publishRequestHandledEvent(request, response, startTime, failureCause); } } // 由子类来实现 protected abstract void doService(HttpServletRequest request, HttpServletResponse response) throws Exception;}
3.6. DispatcherServlet
DispatcherServlet
次要扩大了 2 个办法:onRefresh
、doService
,所以来看看 DispatcherServlet 是如何实现的
3.6.1. DispatcherServlet.onRefresh
DispatcherServlet.onRefresh
public class DispatcherServlet extends FrameworkServlet { @Override protected void onRefresh(ApplicationContext context) { initStrategies(context); } protected void initStrategies(ApplicationContext context) { // 初始化Multipart文件上传解决 initMultipartResolver(context); // 初始化本地化解决 initLocaleResolver(context); // 初始化主题解决 initThemeResolver(context); // 初始化处理器映射 initHandlerMappings(context); // 初始化处理器适配 initHandlerAdapters(context); // 初始化处理器异样 initHandlerExceptionResolvers(context); // 初始化视图查找解决 initRequestToViewNameTranslator(context); // 初始化视图解析解决 initViewResolvers(context); // 初始化内存暂存session数据管理器 initFlashMapManager(context); } private void initMultipartResolver(ApplicationContext context) { try { // 获取bean this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class); // ... 代码省略 } catch (NoSuchBeanDefinitionException ex) { // ... 代码省略 } } private void initLocaleResolver(ApplicationContext context) { try { // 获取bean this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class); // ... 代码省略 } catch (NoSuchBeanDefinitionException ex) { // ... 代码省略 } } private void initThemeResolver(ApplicationContext context) { try { // 获取bean this.themeResolver = context.getBean(THEME_RESOLVER_BEAN_NAME, ThemeResolver.class); // ... 代码省略 } catch (NoSuchBeanDefinitionException ex) { // ... 代码省略 } } private void initFlashMapManager(ApplicationContext context) { try { // 获取bean this.flashMapManager = context.getBean(FLASH_MAP_MANAGER_BEAN_NAME, FlashMapManager.class); } catch (NoSuchBeanDefinitionException ex) { // 没有bean,则获取默认策略 this.flashMapManager = getDefaultStrategy(context, FlashMapManager.class); } }}
3.6.1.1. DispatcherServlet.initHandlerMappings
DispatcherServlet.initHandlerMappings
public class DispatcherServlet extends FrameworkServlet { private void initHandlerMappings(ApplicationContext context) { this.handlerMappings = null; // 默认是探测所有的HandlerMapping,包含父上下文 if (this.detectAllHandlerMappings) { Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerMappings = new ArrayList<>(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.handlerMappings); } } else { // 否则间接获取bean try { HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class); this.handlerMappings = Collections.singletonList(hm); } catch (NoSuchBeanDefinitionException ex) {} } // 如果以上两种都没有定义,则获取默认的解决策略 if (this.handlerMappings == null) { this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class); } // ... 代码省略 } // 获取默认的解决策略 protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) { // 尝试从DispatcherServlet.properties文件中加载 if (defaultStrategies == null) { try { ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource); } catch (IOException ex) { throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage()); } } String key = strategyInterface.getName(); String value = defaultStrategies.getProperty(key); if (value != null) { String[] classNames = StringUtils.commaDelimitedListToStringArray(value); List<T> strategies = new ArrayList<>(classNames.length); for (String className : classNames) { try { Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader()); // 创立bean Object strategy = createDefaultStrategy(context, clazz); // 装载到 strategies 中 strategies.add((T) strategy); } catch (ClassNotFoundException ex) { // ... 代码省略 } catch (LinkageError err) { // ... 代码省略 } } return strategies; } else { return Collections.emptyList(); } } // 创立bean protected Object createDefaultStrategy(ApplicationContext context, Class<?> clazz) { return context.getAutowireCapableBeanFactory().createBean(clazz); }}
DispatcherServlet.properties 文件(开发者不能自定义笼罩)如下:
# Default implementation classes for DispatcherServlet's strategy interfaces.# Used as fallback when no matching beans are found in the DispatcherServlet context.# Not meant to be customized by application developers.org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolverorg.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolverorg.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\ org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\ org.springframework.web.servlet.function.support.RouterFunctionMappingorg.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\ org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\ org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter,\ org.springframework.web.servlet.function.support.HandlerFunctionAdapterorg.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\ org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\ org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolverorg.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslatororg.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolverorg.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager
DispatcherServlet.properties
文件中指明:
- 把
AcceptHeaderLocaleResolver
作为默认的本地化解析器 - 把
FixedThemeResolver
作为默认的主题解析器 - 把
BeanNameUrlHandlerMapping, RequestMappingHandlerMapping, RouterFunctionMapping
作为默认的处理器映射组件 - 把
HttpRequestHandlerAdapter, SimpleControllerHandlerAdapter, RequestMappingHandlerAdapter, HandlerFunctionAdapter
作为默认的处理器适配组件 - 把
ExceptionHandlerExceptionResolver, ResponseStatusExceptionResolver, DefaultHandlerExceptionResolver
作为默认的处理器异样解析器 - 把
DefaultRequestToViewNameTranslator
作为默认的视图查找处理器 - 把
InternalResourceViewResolver
作为默认的视图解析器 - 把
SessionFlashMapManager
作为默认的内存暂存 session 数据管理器
3.6.1.2. DispatcherServlet.initHandlerAdapters
DispatcherServlet.initHandlerAdapters
public class DispatcherServlet extends FrameworkServlet { private void initHandlerAdapters(ApplicationContext context) { this.handlerAdapters = null; // 默认是探测所有的HandlerAdapter,包含父上下文 if (this.detectAllHandlerAdapters) { Map<String, HandlerAdapter> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerAdapters = new ArrayList<>(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.handlerAdapters); } } else { // 否则间接获取bean try { HandlerAdapter ha = context.getBean(HANDLER_ADAPTER_BEAN_NAME, HandlerAdapter.class); this.handlerAdapters = Collections.singletonList(ha); } catch (NoSuchBeanDefinitionException ex) {} } // 如果以上两种都没有定义,则获取默认的解决策略 if (this.handlerAdapters == null) { this.handlerAdapters = getDefaultStrategies(context, HandlerAdapter.class); } }}
3.6.1.3. DispatcherServlet.initHandlerExceptionResolvers
DispatcherServlet.initHandlerExceptionResolvers
public class DispatcherServlet extends FrameworkServlet { private void initHandlerExceptionResolvers(ApplicationContext context) { this.handlerExceptionResolvers = null; // 默认是探测所有的HandlerExceptionResolver,包含父上下文 if (this.detectAllHandlerExceptionResolvers) { Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils .beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerExceptionResolvers = new ArrayList<>(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers); } } else { // 否则间接获取bean try { HandlerExceptionResolver her = context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME, HandlerExceptionResolver.class); this.handlerExceptionResolvers = Collections.singletonList(her); } catch (NoSuchBeanDefinitionException ex) {} } // 如果以上两种都没有定义,则获取默认的解决策略 if (this.handlerExceptionResolvers == null) { this.handlerExceptionResolvers = getDefaultStrategies(context, HandlerExceptionResolver.class); } }}
3.6.1.4. DispatcherServlet.initRequestToViewNameTranslator
DispatcherServlet.initRequestToViewNameTranslator
public class DispatcherServlet extends FrameworkServlet { private void initRequestToViewNameTranslator(ApplicationContext context) { try { // 获取bean this.viewNameTranslator = context.getBean(REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME, RequestToViewNameTranslator.class); } catch (NoSuchBeanDefinitionException ex) { // 如果没有定义bean,则获取默认的解决策略 this.viewNameTranslator = getDefaultStrategy(context, RequestToViewNameTranslator.class); } }}
3.6.1.5. DispatcherServlet.initViewResolvers
DispatcherServlet.initViewResolvers
public class DispatcherServlet extends FrameworkServlet { private void initViewResolvers(ApplicationContext context) { this.viewResolvers = null; // 默认是探测所有的ViewResolver,包含父上下文 if (this.detectAllViewResolvers) { Map<String, ViewResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false); if (!matchingBeans.isEmpty()) { this.viewResolvers = new ArrayList<>(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.viewResolvers); } } else { // 否则间接获取bean try { ViewResolver vr = context.getBean(VIEW_RESOLVER_BEAN_NAME, ViewResolver.class); this.viewResolvers = Collections.singletonList(vr); } catch (NoSuchBeanDefinitionException ex) {} } // 如果以上两种都没有定义,则获取默认的解决策略 if (this.viewResolvers == null) { this.viewResolvers = getDefaultStrategies(context, ViewResolver.class); } }}
3.6.2. DispatcherServlet.doService
刚刚解析完了 DispatcherServlet.onRefresh
,当初来看看 DispatcherServlet.doService
public class DispatcherServlet extends FrameworkServlet { @Override protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception { // ... 代码省略 // 给申请对象增加一些上下文数据 request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext()); request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver); request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver); request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); // ... 代码省略 try { doDispatch(request, response); } finally { // ... 代码省略 } } protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; // 处理器链 HandlerExecutionChain mappedHandler = null; // 是Multipart文件上传 boolean multipartRequestParsed = false; // 异步解决管理器 WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { // 检测Multipart文件上传 processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // 获取处理器,从handlerMappings中查找合乎申请的处理器 mappedHandler = getHandler(processedRequest); if (mappedHandler == null) { // 未找到处理器,404 noHandlerFound(processedRequest, response); return; } // 获取处理器适配器,从handlerAdapters中查找合乎处理器的适配器 HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); String method = request.getMethod(); // 如果是GET或HEAD申请,查看Last-Modified 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; } } // 前置解决,调用处理器的preHandle办法,如果有一个不胜利,返回 if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // 调用处理器 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); // ... 代码省略 // 如果没有视图名字,增加默认的视图名 applyDefaultViewName(processedRequest, mv); // 后置解决,调用处理器的postHandle办法 mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { // ... 代码省略 } catch (Throwable err) { // ... 代码省略 } // 解决handler返回的后果 processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { // ... 代码省略 } catch (Throwable err) { // ... 代码省略 } finally { // ... 代码省略 } } // 解决handler返回的后果 private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv, @Nullable Exception exception) throws Exception { boolean errorView = false; if (exception != null) { // ... 代码省略,如果有异样,调用handlerExceptionResolvers解决 } if (mv != null && !mv.wasCleared()) { // 渲染视图 render(mv, request, response); if (errorView) { WebUtils.clearErrorRequestAttributes(request); } } // ... 代码省略 } // 渲染视图 protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception { // ... 代码省略 View view; String viewName = mv.getViewName(); if (viewName != null) { // 调用viewResolvers来解析视图 view = resolveViewName(viewName, mv.getModelInternal(), locale, request); // ... 代码省略 } else { // ... 代码省略 } // ... 代码省略 try { if (mv.getStatus() != null) { // 设置http状态码 response.setStatus(mv.getStatus().value()); } // 实在渲染 view.render(mv.getModelInternal(), request, response); } catch (Exception ex) { // ... 代码省略 } }}
3.6.3. 须要前面再解析的几个点
DispatcherServlet
这个类的解析基本上就差不多了,但还有几点没有解析:
- FrameworkServlet(L702):
ConfigurableWebApplicationContext.refresh
- DispatcherServlet(L514):
ApplicationContext.getBean
- DispatcherServlet.properties 文件中定义的策略解决
- DispatcherServlet(L1393):
View.render
这几点,咱们前面再来解析。
4. ContextLoaderListener
先来看看 ContextLoaderListener
的继承关系:
- ContextLoader - ContextLoaderListener
ContextLoaderListener 比较简单,只有两个监听事件办法
public class ContextLoaderListener extends ContextLoader implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent event) { // ContextLoader.initWebApplicationContext initWebApplicationContext(event.getServletContext()); } @Override public void contextDestroyed(ServletContextEvent event) { // ContextLoader.closeWebApplicationContext closeWebApplicationContext(event.getServletContext()); // 销毁上下文中以"org.springframework."结尾的可销毁bean ContextCleanupListener.cleanupAttributes(event.getServletContext()); }}
ContextLoader 的动态初始化
public class ContextLoader { static { try { // 从ContextLoader.properties文件中加载默认的策略 ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource); } catch (IOException ex) { throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage()); } }}
ContextLoader.properties 文件的内容如下:
# Default WebApplicationContext implementation class for ContextLoader.# Used as fallback when no explicit context implementation has been specified as context-param.# Not meant to be customized by application developers.org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext
ContextLoader.properties
文件中指明应用 XmlWebApplicationContext
作为默认的 Web 利用上下文环境
再来看看 ContextLoader 的 initWebApplicationContext
和 closeWebApplicationContext
4.1. ContextLoaderListener.initWebApplicationContext
ContextLoaderListener.initWebApplicationContext
public class ContextLoader { public WebApplicationContext initWebApplicationContext(ServletContext servletContext) { // ... 代码省略 try { // 如果没有上下文对象,则创立一个新的上下文 // 并调用 configureAndRefreshWebApplicationContext(cwac) 配置并刷新新的上下文 // 默认应用 XmlWebApplicationContext(基于XML加载)作为利用上下文 if (this.context == null) { this.context = createWebApplicationContext(servletContext); } if (this.context instanceof ConfigurableWebApplicationContext) { ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context; // 未激活 if (!cwac.isActive()) { if (cwac.getParent() == null) { ApplicationContext parent = loadParentContext(servletContext); cwac.setParent(parent); } // 配置并刷新利用上下文 configureAndRefreshWebApplicationContext(cwac, servletContext); } } // 把上下文注册到ServletContext中 servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context); // ... 代码省略 return this.context; } catch (RuntimeException | Error ex) { // ... 代码省略 } }}
ContextLoader.configureAndRefreshWebApplicationContext
与 FrameworkServlet.configureAndRefreshWebApplicationContext
的解决基本上统一。
也就是说,当容器启动(如 Tomcat、Jetty、Undertow 等)时,Spring 框架会主动进行初始化。
4.2. ContextLoaderListener.closeWebApplicationContext
ContextLoaderListener.closeWebApplicationContext
public class ContextLoader { public void closeWebApplicationContext(ServletContext servletContext) { try { if (this.context instanceof ConfigurableWebApplicationContext) { // 调用上下文对象的close办法 ((ConfigurableWebApplicationContext) this.context).close(); } } finally { // ... 代码省略 } }}
5. 综述
DispatcherServlet.init
与 ContextLoaderListener.contextInitialized
都会进行利用上下文的初始化,次要过程是:
- 初始化 Web 利用上下文,默认应用
XmlWebApplicationContext
(基于 XML 加载)作为利用上下文,并调用refresh
办法 - 实例化由
globalInitializerClasses
和contextInitializerClasses
定义的类 - 实例化 WebMVC 必要的组件:
MultipartResolver
,LocaleResolver
,ThemeResolver
,HandlerMapping
,HandlerAdapter
,HandlerExceptionResolver
,RequestToViewNameTranslator
,ViewResolver
,FlashMapManager
每个申请都会进入到 DispatcherServlet.service
,其次要过程是:
- 初始化申请对象,以便利用后续解决
- 解决 Multipart 文件上传,获取处理器解决以后申请
- 如果以后申请解决产生异样,进行异样解决
- 进行视图渲染
6. 未完
到这里为止,剖析仅仅止于 DispatcherServlet
与 ContextLoaderListener
两个类,下一篇将深刻其余类,持续摸索。
ConfigurableWebApplicationContext.refresh
刷新上下文ApplicationContext.getBean
从上下文中获取 beanDispatcherServlet.properties
文件中定义的策略解决ContextLoader.properties
文件中定义的策略解决View.render
视图渲染
后续
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