SpringMVC——DispatcherServlet的IoC容器(Web应用的IoC容器的子容器)创建过程

1 　　<!--WebApplicationContext配置参数-->
2 　　<context-param>
3     　　<param-name>contextConfigLocation</param-name>
4     　　<param-value>classpath*:applicationContext.xml</param-value>
5 　　</context-param>
6    <!--注册ContextLoaderListener,加载根应用上下文-->
7 　　<listener>
8     　　<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
9 　　</listener>

 1     <!--注册DispatcherServlet，加载应用上下文-->
 2     <servlet>
 3         <servlet-name>springmvc</servlet-name>
 4         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
 5         <init-param>
 6             <param-name>contextConfigLocation</param-name>
 7             <param-value>classpath*:spring-servlet.xml</param-value>    <!--若不显示添加配置文件路径,则会默认加载servlt-name的名字+"-servlet.xml"-->
 8         </init-param>
 9         <load-on-startup>1</load-on-startup>
10     </servlet>
11     <!--servlet映射-->
12     <servlet-mapping>
13         <servlet-name>springmvc</servlet-name>
14         <url-pattern>/</url-pattern>
15     </servlet-mapping>

//GenericServlet.java
public void init(ServletConfig config) throws ServletException {
    this.config = config;
    this.init();
}
...
public void init() throws ServletException {

}
...

//HttpServletBean.javapublic final void init() throws ServletException {
    if (logger.isDebugEnabled()) {
        logger.debug("Initializing servlet '" + getServletName() + "'");
    }

    // Set bean properties from init parameters.从初始化参数中设置bean属性
    try {
        PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
        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.调用子类的initServletBean进行具体的初始化
    initServletBean();

    if (logger.isDebugEnabled()) {
        logger.debug("Servlet '" + getServletName() + "' configured successfully");
    }
}
...
//具体的初始化交由子类去完成,即FrameworkServlet
protected void initServletBean() throws ServletException {
}

//FrameServlet.java
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();   //在这里不是初始化Spring根应用上下文(Web应用的IoC容器),而是初始化SpringMVC的Servlet上下文创建自己所持有的IoC容器.如果没有则调用createWebApplicationContext方法进行创建.并将根应用上下文作为它的双亲上下文
        initFrameworkServlet(); //此方法也没有给出具体实现,再其子类DispatcherServlet也没有对它重写.
    }
    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");
    }
}
...
//在所有的bean配置参数和WebApplicationContext被加载后会调用此方法,默认实现为空,它的子类可以重写此方法来实现需要的初始化操作.子类DispatcherServlet并没有重写.
protected void initFrameworkServlet() throws ServletException {
}

//DispatcherServlet.java
protected void initStrategies(ApplicationContext context) {
    initMultipartResolver(context);
    initLocaleResolver(context);
    initThemeResolver(context);
    initHandlerMappings(context);    //这里就是为http请求找到相应的Controller控制器
    initHandlerAdapters(context);
    initHandlerExceptionResolvers(context);
    initRequestToViewNameTranslator(context);
    initViewResolvers(context);
    initFlashMapManager(context);
}

//FrameworkServlet.java
protected WebApplicationContext initWebApplicationContext() {
    ......
    if (this.webApplicationContext != null) {
        ......
        configureAndRefreshWebApplicationContext(cwac);     //在此方法中调用的onRefresh
        ......
    }
    if (wac == null) {
        wac = createWebApplicationContext(rootContext);     //此方法中最后也是调用的configureAndRefreshWebApplicationContext方法
    }

    if (!this.refreshEventReceived) {
        onRefresh(wac);
    }
    ......
    return wac;
}