java-springmvc 01

springmvc也是在spring framework中的，不是一个单独的项目

MVC就是和Tomcat有关。

01.MVC启动的第一步，启动Tomcat（这个和springboot的run方法启动Tomcat有关）

02.SpringMVC中，最为核心的就是DispatcherServlet，在启动Tomcat的过程中：

1. Tomcat会先创建DispatcherServlet对象(这一步在手写springboot框架中已经写到，Tomcat在启动的时候会启动DispatcherServlet)
2. 然后调用DispatcherServlet对象的init()

DispatcherServlet对象的init()

01.DispatcherServlet类的init()

public class DispatcherServlet extends FrameworkServlet {
//DispatcherServlet中没有init方法，在父类中找
}

HttpServletBean类

@Override
	public final void init() throws ServletException {
		// 解析 init-param 并封装只 pvs 中(xml)
		PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
		if (!pvs.isEmpty()) {
			try {
				// 将当前的这个 Servlet 类转化为一个 BeanWrapper，从而能够以 Spring 的方法来对 init-param 的值进行注入
				BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
				ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
				bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
				initBeanWrapper(bw);
				// 属性注入
				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.
		// 初始化Servlet，创建Spring容器
		initServletBean();
	}

DispatcherServlet 继承 httpservletbean

02.FrameworkServlet

	public static final Class DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;

03.initServletBean

	protected final void initServletBean() throws ServletException {
		getServletContext().log("Initializing Spring " + getClass().getSimpleName() + " '" + getServletName() + "'");
		if (logger.isInfoEnabled()) {
			logger.info("Initializing Servlet '" + getServletName() + "'");
		}
		long startTime = System.currentTimeMillis();
		try {
			this.webApplicationContext = initWebApplicationContext();
			// 空方法，无实现·
			initFrameworkServlet();
		}
		catch (ServletException | RuntimeException ex) {
			logger.error("Context initialization failed", ex);
			throw ex;
		}
		if (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";
			logger.debug("enableLoggingRequestDetails='" + this.enableLoggingRequestDetails +
					"': request parameters and headers will be " + value);
		}
		if (logger.isInfoEnabled()) {
			logger.info("Completed initialization in " + (System.currentTimeMillis() - startTime) + " ms");
		}
	}

04initWebApplicationContext

protected WebApplicationContext initWebApplicationContext() {
		// 获得ContextLoaderListener存的父容器
		WebApplicationContext rootContext =
				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = null;
		if (this.webApplicationContext != null) {
			// 获得子容器
			wac = this.webApplicationContext;
			if (wac instanceof ConfigurableWebApplicationContext) {
				ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
				if (!cwac.isActive()) {
					// 如果没有设置父容器   spring  doGetBean
					if (cwac.getParent() == null) {
						cwac.setParent(rootContext);
					}
					// 配置并且加载子容器
					configureAndRefreshWebApplicationContext(cwac);
				}
			}
		}
		if (wac == null) {
			// 从servlet上下文根据名字从域里面获取
			wac = findWebApplicationContext();
		}
		if (wac == null) {
			// xml会在这里创建
			wac = createWebApplicationContext(rootContext);
		}
		//refreshEventReceived 它会在容器加载完设置为true (通过事件onApplicationEvent)
		// springboot在这初始化组件
		if (!this.refreshEventReceived) {
			synchronized (this.onRefreshMonitor) {
				onRefresh(wac);
			}
		}
		if (this.publishContext) {
			// 将当前容器放到servlet域中， 可以再创建子容器
			String attrName = getServletContextAttributeName();
			getServletContext().setAttribute(attrName, wac);
		}
		return wac;
	}