SpringMVC中的DispatcherServlet初始化流程详解

    protected final void initServletBean() throws ServletException {
        this.getServletContext().log("Initializing Spring " + this.getClass().getSimpleName() + " \'" + this.getServletName() + "\'");
        if(this.logger.isInfoEnabled()) {
            this.logger.info("Initializing Servlet \'" + this.getServletName() + "\'");
        }
        long startTime = System.currentTimeMillis();
        try {
            /**
            这里初始化上下文
            **/
            this.webApplicationContext = this.initWebApplicationContext();
            this.initFrameworkServlet();
        } catch (RuntimeException | ServletException var4) {
            this.logger.error("Context initialization failed", var4);
            throw var4;
        }
        if(this.logger.isDebugEnabled()) {
            String value = this.enableLoggingRequestDetails?"shown which may lead to unsafe logging of potentially sensitive data":"masked to prevent unsafe logging of potentially sensitive data";
            this.logger.debug("enableLoggingRequestDetails=\'" + this.enableLoggingRequestDetails + "\': request parameters and headers will be " + value);
        }
        if(this.logger.isInfoEnabled()) {
            this.logger.info("Completed initialization in " + (System.currentTimeMillis() - startTime) + " ms");
        }
    }

   protected WebApplicationContext initWebApplicationContext() {
        /**
        若webApplicationContext不为空的时候从SerlvetContext去出根上下文作为它的双亲上下文
        **/
        WebApplicationContext rootContext = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
        WebApplicationContext wac = null;
        if(this.webApplicationContext != null) {
            wac = this.webApplicationContext;
            if(wac instanceof ConfigurableWebApplicationContext) {
                ConfigurableWebApplicationContext attrName = (ConfigurableWebApplicationContext)wac;
                if(!attrName.isActive()) {
                    if(attrName.getParent() == null) {
                        attrName.setParent(rootContext);
                    }
                    this.configureAndRefreshWebApplicationContext(attrName);
                }
            }
        }
        if(wac == null) {
            wac = this.findWebApplicationContext();
        }
        if(wac == null) {
            wac = this.createWebApplicationContext(rootContext);
        }
        //这里通过调用子类DispatcherServlet实现的onRefresh方法
        if(!this.refreshEventReceived) {
            this.onRefresh(wac);
        }
        //把当前建立好的上下文存到ServletContext里面去
        if(this.publishContext) {
            String attrName1 = this.getServletContextAttributeName();
            this.getServletContext().setAttribute(attrName1, wac);
        }
        return wac;
    }

    
//该属性默认为true
    private boolean detectAllHandlerMappings = true;
private void initHandlerMappings(ApplicationContext context) {
        this.handlerMappings = null;
        //这里面的逻辑是从导入所有的HandlerMappingBean，这些Bean有可能存在与双亲容器中，也可能在DispathcerServlet持有的容器的，这里detectAllHandlerMappings默认为true,默认从所有容器中导入
        if(this.detectAllHandlerMappings) {
            Map hm = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
            if(!hm.isEmpty()) {
                this.handlerMappings = new ArrayList(hm.values());
                AnnotationAwareOrderComparator.sort(this.handlerMappings);
            }
        } else {
            //否则通过直接通过名字从当前的IOC容器中通过getBean方法获取handlerMapping
            try {
                HandlerMapping hm1 = (HandlerMapping)context.getBean("handlerMapping", HandlerMapping.class);
                this.handlerMappings = Collections.singletonList(hm1);
            } catch (NoSuchBeanDefinitionException var3) {
                ;
            }
        }
        //如果还是没有找到hadlerMapping就需要设定默认的handlerMappings了
        if(this.handlerMappings == null) {
            this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class);
            if(this.logger.isTraceEnabled()) {
                this.logger.trace("No HandlerMappings declared for servlet \'" + this.getServletName() + "\': using default strategies from DispatcherServlet.properties");
            }
        }
    }