SpringMVC源码阅读(1)

试图用比较简的方法，一看就懂，直接来图：

说明：

粉色代表spring及springmvc组件初始化过程（起始点，是servlet的init方法）

蓝色代表springmvc处理请求的过程（起始点，是servlet的init方法）

public interface Servlet {
    public void init(ServletConfig config) throws ServletException;
    public ServletConfig getServletConfig();
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException;
    public String getServletInfo();
    public void destroy();
}

7是springMVC把spring初始的上下文，合并进来的地方，，，跳过一个标号10，嘿嘿

13是springMVC初始化9大组件地方

7是springMVC处理请求的核心流程代码

总结：

Spring在ioc的初始化步骤中，在bean的初始化前后，都有预留开发者再次定制的路径。

Spring mvc也同样预留了类似的途径。

ContextLoaderListener就是Spring根上下文（WebApplicationContext）生命周期监控的触发点。它规范了Spring根上下文根上下文容器生命周期的回调。

WebApplicationContext的初始化执行者是ContextLoaderListener的父类ContextLoader

org.springframework.web.context.ContextLoaderListener.contextInitialized(ServletContextEvent)

    public void contextInitialized(ServletContextEventevent){

        initWebApplicationContext(event.getServletContext());

    }

org.springframework.web.context.ContextLoader.initWebApplicationContext(ServletContext)

    public WebApplicationContextinitWebApplicationContext(ServletContextservletContext) {

        if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null){//这里一定不存在，因为，这里一定是首先启动的初始化的地方。然后才是DispatcherServlet使用这里启动的ioc作为父容器。

            throw new IllegalStateException(

                   "Cannot initialize context because there is alreadya root application context present - "+

                   "check whether you have multiple ContextLoader*definitions in your web.xml!");

        }

 

        Loglogger= LogFactory.getLog(ContextLoader.class);

        servletContext.log("Initializing Spring rootWebApplicationContext");

        if (logger.isInfoEnabled()) {

            logger.info("Root WebApplicationContext: initializationstarted");

        }

        long startTime = System.currentTimeMillis();

 

        try {

            // Store context in local instance variable, to guaranteethat

            // it is available on ServletContext shutdown.

            if (this.context ==null) {

                this.context =createWebApplicationContext(servletContext);

            }

            if (this.contextinstanceofConfigurableWebApplicationContext) {

                ConfigurableWebApplicationContextcwac= (ConfigurableWebApplicationContext)this.context;

                if (!cwac.isActive()) {

                   // The context has not yet been refreshed -> provideservices such as

                   // setting the parent context, setting the application contextid, etc

                   if (cwac.getParent() ==null) {

                       // The context instance was injected without an explicitparent ->

                       // determine parent for root web application context, ifany.

                       ApplicationContextparent= loadParentContext(servletContext);

                       cwac.setParent(parent);

                   }

                   configureAndRefreshWebApplicationContext(cwac,servletContext);

                }

            }

        servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE,this.context);

 

            ClassLoaderccl= Thread.currentThread().getContextClassLoader();

            if (ccl == ContextLoader.class.getClassLoader()) {

                currentContext=this.context;

            }

            else if (ccl != null) {

                currentContextPerThread.put(ccl,this.context);

            }

 

            if (logger.isDebugEnabled()) {

                logger.debug("Published root WebApplicationContext asServletContext attribute with name ["+

                       WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE +"]");

            }

            if (logger.isInfoEnabled()) {

                longelapsedTime = System.currentTimeMillis()-startTime;

                logger.info("Root WebApplicationContext: initializationcompleted in " +elapsedTime +" ms");

            }

 

            return this.context;

        }

        catch (RuntimeExceptionex) {

            logger.error("Context initialization failed",ex);

        servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE,ex);

            throwex;

        }

        catch (Errorerr) {

            logger.error("Context initialization failed",err);

        servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE,err);

            throwerr;

        }

    }