spring零配置-取代web.xml

step1

SpringServletContainerInitializer.java

该类继承ServletContainerInitializer，实现了与servlet容器的集成。在class上添加了注解@HandlesTypes，指定了我们我们的应用程序要启动加载的类型。onStartup方法的第一个参数是一个set集合，集合中的class对应就是注解@HandlesTypes中指定的类型。@Overridepublic void onStartup(Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)        throws ServletException {    //存储WebApplicationInitializer实例。在本项目中有两个实例:WebContextInitializer.java和SecurityWebApplicationInitializer.java    List<WebApplicationInitializer> initializers = new LinkedList<WebApplicationInitializer>();    if (webAppInitializerClasses != null) {        for (Class<?> waiClass : webAppInitializerClasses) {            ...            initializers.add((WebApplicationInitializer) waiClass.newInstance());            ...         }    }    ...    AnnotationAwareOrderComparator.sort(initializers);    servletContext.log("Spring WebApplicationInitializers detected on classpath: " + initializers);    //遍历WebApplicationInitializer实例，依次调用实例的onStartup方法。    for (WebApplicationInitializer initializer : initializers) {        initializer.onStartup(servletContext);    }}

step2:

SecurityWebApplicationInitializer.java

调用改类的onStartup方法。调用父类的onStartup方法：AbstractSecurityWebApplicationInitializer.javapublic final void onStartup(ServletContext servletContext) throws ServletException {    ...    //registerFilter(servletContext, true, filterName, springSecurityFilterChain);    //向ServletContext中注册spring安全框架的Filter，在web.xml中配置过springSecurity框架的应该都知道    insertSpringSecurityFilterChain(servletContext);    ...}

step3:

WebContextInitializer.java

调用该类的onStartup方法。调用父类AbstractContextLoaderInitializer.java的onstartup方法//注册ContextLoaderListener，在web.xml中配置过spring框架的人都知道@Overridepublic void onStartup(ServletContext servletContext) throws ServletException {    registerContextLoaderListener(servletContext);}protected void registerContextLoaderListener(ServletContext servletContext) {    //创建spring的根应用上下文    WebApplicationContext rootAppContext = createRootApplicationContext();    if (rootAppContext != null) {        ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);        listener.setContextInitializers(getRootApplicationContextInitializers());        servletContext.addListener(listener);    }    else {        logger.debug("No ContextLoaderListener registered, as " +                "createRootApplicationContext() did not return an application context");    }}调用父类AbstractDispatcherServletInitializer.java的onstartup方法//注册DispatcherServlet，在web.xml中配置过springMVC框架的人都知道@Overridepublic void onStartup(ServletContext servletContext) throws ServletException {    super.onStartup(servletContext);    registerDispatcherServlet(servletContext);}protected void registerDispatcherServlet(ServletContext servletContext) {    String servletName = getServletName();    Assert.hasLength(servletName, "getServletName() must not return empty or null");    //创建springMVC的应用上下文    WebApplicationContext servletAppContext = createServletApplicationContext();    ...    FrameworkServlet dispatcherServlet = createDispatcherServlet(servletAppContext);    dispatcherServlet.setContextInitializers(getServletApplicationContextInitializers());    ServletRegistration.Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);    ...}//创建spring应用上下文和创建springMVC应用上下文的实现在AbstractAnnotationConfigDispatcherServletInitializer.java中//根上下文的创建@Overrideprotected WebApplicationContext createRootApplicationContext() {    //获取要加载的class，由子类实现    Class<?>[] configClasses = getRootConfigClasses();    if (!ObjectUtils.isEmpty(configClasses)) {        AnnotationConfigWebApplicationContext rootAppContext = new AnnotationConfigWebApplicationContext();        rootAppContext.register(configClasses);        return rootAppContext;    }    else {        return null;    }}//springMVC上下文的创建@Overrideprotected WebApplicationContext createServletApplicationContext() {    AnnotationConfigWebApplicationContext servletAppContext = new AnnotationConfigWebApplicationContext();    //获取要加载的class,由子类实现    Class<?>[] configClasses = getServletConfigClasses();    if (!ObjectUtils.isEmpty(configClasses)) {        servletAppContext.register(configClasses);    }    return servletAppContext;}

step4

listener,filter,servlet通过编码的方式配置到ServletContext后，后面的启动过程和xml配置一直，spring容器的启动入口在ContextLoaderListener,springMVC的启动入口在DispatchServlet,springSecurity的启动入口在SecurityFilterChain