Spring IOC容器通过ServletContextListener对servlet容器的生命周期监听，从而实现了IOC的启动和销毁。
注意：
1.分析框架代码时，要常使用类继承、调用关系等快捷键，可以更高效的学习，快捷键可以设置成你习惯的按键；
2.本文重在怎么自我分析框架代码，所以对其中解析需自己实际跟踪代码实践方可；
3.spring源代码版本 spring-framework-3.2.1.RELEASE。
预览
javax.servlet.ServletContext，Servlet容器接口。
javax.servlet.ServletContextListener，Servlet容器生命周期监听接口。
org.springframework.web.context.ContextLoaderListener，Spring IOC容器生命周期监听类。
org.springframework.web.context.ContextLoader，Spring
IOC容器启动和销毁。
<listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener>
public void contextInitialized ( ServletContextEvent sce ); // ServletContext启动时触发
public void contextDestroyed ( ServletContextEvent sce ); // ServletContext销毁时触发org.springframework.web.context.ContextLoaderListener
public void contextInitialized(ServletContextEvent event) {
this.contextLoader = createContextLoader();
if (this.contextLoader == null) {
this.contextLoader = this;
}
// 对spring ioc容器进行初始化
this.contextLoader.initWebApplicationContext(event.getServletContext());
}org.springframework.web.context.ContextLoader
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
// 是否已经加载IOC容器
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context present - " +
"check whether you have multiple ContextLoader* definitions in your web.xml!");
}
Log logger = LogFactory.getLog(ContextLoader.class);
servletContext.log("Initializing Spring root WebApplicationContext");
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();
try {
// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
if (this.context == null) {
this.context = createWebApplicationContext(servletContext);
}
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent ->
// determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);
cwac.setParent(parent);
}
// 此方法是刷新初始化IOC容器的地方
configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
// IOC容器加载后，将IOC容器保存于ServletContext容器中
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
...
}org.springframework.web.context.ContextLoader
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
if (idParam != null) {
wac.setId(idParam);
}
else {
// Generate default id...
if (sc.getMajorVersion() == 2 && sc.getMinorVersion() < 5) {
// Servlet <= 2.4: resort to name specified in web.xml, if any.
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(sc.getServletContextName()));
}
else {
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(sc.getContextPath()));
}
}
}
wac.setServletContext(sc);
String initParameter = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (initParameter != null) {
wac.setConfigLocation(initParameter);
}
customizeContext(sc, wac);
// 熟悉的refresh()对Spring IOC容器进行加载，接下来的步骤就是 "自我分析-Spring IOC"文脏中的内容
wac.refresh();
}org.springframework.web.context.ContextLoaderListener
public void contextDestroyed(ServletContextEvent event) {
if (this.contextLoader != null) {
this.contextLoader.closeWebApplicationContext(event.getServletContext());
}
ContextCleanupListener.cleanupAttributes(event.getServletContext());
} 具体清理销毁了spring的什么东西，自己再跟踪下代码即可。
原文地址：http://blog.csdn.net/hai8902882/article/details/39434489
