SpringMvc 初始化入口

た入场券 2022-06-02 02:29 221阅读 0赞

web工程中servlet能够映射到一个http请求路径，且每个servlet有其自己的生命周期，其使用init函数进行初始化，用service函数提供服务。  
SpringMVC利用servlet这些特点，将容器的初始化巧妙的融合在了servlet的初始化过程中。  
所以容器的初始化触发点在servlet init中。

org.springframework.web.servlet.HttpServletBean.init()函数。
    @Override
        public final void init() throws ServletException {
            if (logger.isDebugEnabled()) {
                logger.debug("Initializing servlet '" + getServletName() + "'");
            }
    
            // 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();//这里被子类覆盖
    
            if (logger.isDebugEnabled()) {
                logger.debug("Servlet '" + getServletName() + "' configured successfully");
            }
        }

initServletBean();//这里被子类覆盖

@Override
        protected final void initServletBean() throws ServletException {
            getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
            if (this.logger.isInfoEnabled()) {
                this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
            }
            long startTime = System.currentTimeMillis();
    
            try {
                this.webApplicationContext = initWebApplicationContext();//这里是关键位置
                initFrameworkServlet();
            }
            catch (ServletException ex) {
                this.logger.error("Context initialization failed", ex);
                throw ex;
            }
            catch (RuntimeException ex) {
                this.logger.error("Context initialization failed", ex);
                throw ex;
            }
    
            if (this.logger.isInfoEnabled()) {
                long elapsedTime = System.currentTimeMillis() - startTime;
                this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
                        elapsedTime + " ms");
            }
        }

this.webApplicationContext = initWebApplicationContext();//这里是关键位置。定义在org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext()，其中有root上下文和web上下文关系是如何建立的逻辑。