SpringMVC源碼解析系列2-DispatcherServlet

時間 2019-11-17

標籤 springmvc 源碼解析系列 dispatcherservlet 欄目 Spring 简体版

原文原文鏈接

SpringMVC源碼解析系列2-DispatcherServlet
- DispatcherServlet初始化過程
- DispatcherServlet調用過程

DispatcherServlet初始化過程

能夠看到有幾個生命週期接口:java

ApplicationContextAware:保存了spring上下文web

public interface ApplicationContextAware extends Aware {
	//上下文初始化完成後被調用
	void setApplicationContext(ApplicationContext applicationContext) throws BeansException;
}
#org.springframework.web.servlet.FrameworkServlet	
//保存SpringMVC上下文 當經過Spring裝載DispatchServlet時會被調用
@Override
public void setApplicationContext(ApplicationContext applicationContext) {
	if (this.webApplicationContext == null && applicationContext instanceof WebApplicationContext) {
		this.webApplicationContext = (WebApplicationContext) applicationContext;
		this.webApplicationContextInjected = true;
	}
}

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EnvironmentAware:保存了環境變量對象spring

public interface EnvironmentAware extends Aware {
	//環境變量對象初始化完成後被調用
	void setEnvironment(Environment environment);
}
#org.springframework.web.servlet.HttpServletBean
	@Override
	public void setEnvironment(Environment environment) {
		Assert.isInstanceOf(ConfigurableEnvironment.class, environment, "ConfigurableEnvironment required");
		this.environment = (ConfigurableEnvironment) environment;
	}
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Servlet:Servlet生命週期網絡

public interface Servlet {
   //serlvet初始化
    public void init(ServletConfig config) throws ServletException;
    public ServletConfig getServletConfig();
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException;
    public String getServletInfo();
  //serlvet銷燬
    public void destroy();
}
#org.springframework.web.servlet.HttpServletBean
@Override
public final void init() throws ServletException {
	...
	initServletBean();
}
@Override
public void destroy() {
	if (this.webApplicationContext instanceof ConfigurableApplicationContext && !this.webApplicationContextInjected) {
		//銷燬上下文
		((ConfigurableApplicationContext) this.webApplicationContext).close();
	}
}
#org.springframework.web.servlet.FrameworkServlet
DispatcherServlet extends FrameworkServlet 
#org.springframework.web.servlet.FrameworkServlet
@Override
protected final void initServletBean() throws ServletException {
	...
	try {
		this.webApplicationContext = initWebApplicationContext();
		initFrameworkServlet();
	}
	...
}
protected WebApplicationContext initWebApplicationContext() {
	WebApplicationContext rootContext =
			WebApplicationContextUtils.getWebApplicationContext(getServletContext());
	WebApplicationContext wac = null;
	...
	//以spring配置方式時webApplicationContext!=null
	if (this.webApplicationContext != null) {
			wac = this.webApplicationContext;
			if (wac instanceof ConfigurableWebApplicationContext) {
				ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
						cwac.setParent(rootContext);
				}
			}
		}
	if (wac == null) {
		//建立applicationContext
		wac = createWebApplicationContext(rootContext);
	}
	...
	return wac;
}
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
	//XmlWebApplicationContext 
	Class<?> contextClass = getContextClass();
	...
	//建立applicationContext
	ConfigurableWebApplicationContext wac =
			(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
	wac.setEnvironment(getEnvironment());
	//設置parent(ContextLoadListener中建立的applicationContext)
	wac.setParent(parent);
	//讀取contextConfigLocation配置
	wac.setConfigLocation(getContextConfigLocation());
	//refresh()
	configureAndRefreshWebApplicationContext(wac);
	return wac;
}
//當SpringMVC上下初始化完成後會去裝載默認策略(HandlerMapping,HandleAdapter)
protected void initStrategies(ApplicationContext context) {
  //獲取容器中是否有其實現 沒有則加載DispatcherServlet.properties中的默認實現
	initMultipartResolver(context);
	initLocaleResolver(context);
	initThemeResolver(context);
	initHandlerMappings(context);
	initHandlerAdapters(context);
	initHandlerExceptionResolvers(context);
	initRequestToViewNameTranslator(context);
	initViewResolvers(context);
	initFlashMapManager(context);
}
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org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver
org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
	org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping
org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
	org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
	org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter
org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\
	org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
	org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver
org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator
org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver
org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager
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DispatcherServlet調用過程

@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
	//將相關配置設置到request做用於中
	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());
  	...
	request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());
	request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);

	try {
		doDispatch(request, response);
	}
}

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
	...
	try {
		ModelAndView mv = null;
		Exception dispatchException = null;
		try {
			processedRequest = checkMultipart(request);
			multipartRequestParsed = (processedRequest != request);
			//1.調用handlerMapping獲取handlerChain
			mappedHandler = getHandler(processedRequest);
			if (mappedHandler == null || mappedHandler.getHandler() == null) {
				noHandlerFound(processedRequest, response);
				return;
			}
			// 2.獲取支持該handler解析的HandlerAdapter
			HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
          	//前置處理(CORS時用到)
			if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}
			// 3.使用HandlerAdapter完成handler處理
			mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
			//若是是異步請求 直接返回 
			if (asyncManager.isConcurrentHandlingStarted()) {
				return;
			}
			applyDefaultViewName(request, mv);
          	//後置處理
			mappedHandler.applyPostHandle(processedRequest, response, mv);
		}
		catch (Exception ex) {
			dispatchException = ex;
		}
      	//4.異常處理,視圖解析,渲染返回
		processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
	}
	...
}
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {
	boolean errorView = false;
  	//若是HandlerAdapter.handler()執行異常 則進行異常處理
	if (exception != null) {
		...
          Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
      //4.1
        mv = processHandlerException(request, response, handler, exception);
        errorView = (mv != null);
	}


	if (mv != null && !mv.wasCleared()) {
      	//4.2 視圖解析 渲染返回
		render(mv, request, response);
		if (errorView) {
			WebUtils.clearErrorRequestAttributes(request);
		}
	}
}
//異常處理
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
	ModelAndView exMv = null;
	for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) {
      	//使用異常解析器解析異常(相似HandlerAdapter參數解析,調用)
		exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);
		if (exMv != null) {
			break;
		}
    }
  	...
}
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
	//國際化
	Locale locale = this.localeResolver.resolveLocale(request);
	response.setLocale(locale);
	View view;
	if (mv.isReference()) {
		//4.2.1視圖解析
		view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
		...
	}
	else {
		view = mv.getView();
	}
	....
	try {
		if (mv.getStatus() != null) {
			response.setStatus(mv.getStatus().value());
		}
      	//渲染返回
		view.render(mv.getModelInternal(), request, response);
	}
	...
}
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception {
	//視圖解析
	for (ViewResolver viewResolver : this.viewResolvers) {
		View view = viewResolver.resolveViewName(viewName, locale);
		if (view != null) {
			return view;
		}
	}
	return null;
}
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