spring有三种启动方式,使用ContextLoaderServlet,ContextLoader
spring有三种启动方式,使用ContextLoaderServlet,ContextLoaderListener和ContextLoaderPlugIn.
看一下ContextLoaderListener的源码,这是一个ServletContextListener
/**
?? * Initialize the root web application context.
?? */
public void contextInitialized(ServletContextEvent event) {
?? this.contextLoader = createContextLoader();
?? this.contextLoader.initWebApplicationContext(event.getServletContext());
}
?? /**
?? * Create the ContextLoader to use. Can be overridden in subclasses.
?? * @return the new ContextLoader
?? */
protected ContextLoader createContextLoader() {
?? return new ContextLoader();
}
contextLoader的源码
public WebApplicationContext initWebApplicationContext(ServletContext servletContext)
??? throws BeansException {
?? long startTime = System.currentTimeMillis();
?? if (logger.isInfoEnabled()) {
??? logger.info("Root WebApplicationContext: initialization started");
?? }
?? servletContext.log("Loading Spring root WebApplicationContext");
?? try {
??? // Determine parent for root web application context, if any.
??? ApplicationContext parent = loadParentContext(servletContext);
??? WebApplicationContext wac = createWebApplicationContext(servletContext, parent);
??? servletContext.setAttribute(
????? WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, wac);
??? if (logger.isInfoEnabled()) {
???? logger.info("Using context class [" + wac.getClass().getName() +
?????? "] for root WebApplicationContext");
??? }
??? if (logger.isDebugEnabled()) {
???? logger.debug("Published root WebApplicationContext [" + wac +
?????? "] as ServletContext attribute with name [" +
?????? WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
??? }
??? if (logger.isInfoEnabled()) {
???? long elapsedTime = System.currentTimeMillis() - startTime;
???? logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
??? }
??? return wac;
?? }
?? catch (RuntimeException ex) {
??? logger.error("Context initialization failed", ex);
??? servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
??? throw ex;
?? }
?? catch (Error err) {
??? logger.error("Context initialization failed", err);
??? servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
??? throw err;
?? }
}
注意WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE,这里面放了WebApplicationContext,需要使用时从ServletContext取出
可以使用WebApplicationContextUtils得到WebApplicationContext
public static WebApplicationContext getWebApplicationContext(ServletContext sc) {
?? Object attr = sc.?? }
?? return (WebApplicationContext) attr;
}
关键的问题在于struts如何启动的spring的,ContextLoaderPlugIn的源码
// Publish the context as a servlet context attribute.
?? String attrName = getServletContextAttributeName();
?? getServletContext().setAttribute(attrName, wac);
public String getServletContextAttributeName() {
?? return SERVLET_CONTEXT_PREFIX + getModulePrefix();
}
不同加载的Key竟然不同,原因就是WebApplicationContext放在那里的问题,可spring调用的时候会根据WebApplicationContext里面定义的那个名字去找的,问题出在这里
在struts-config.xml中配置
???? <plug-in className="org.springframework.web.struts.ContextLoaderPlugIn">
?????? <set-property property="contextConfigLocation" value="/WEB-INF/applicationContext.xml" />
???? </plug-in>
???? <controller>
???????? <set-property property="processorClass" value="org.springframework.web.struts.DelegatingRequestProcessor" />
???? </controller>
原理是这样的,Struts虽然只能有一个ActionServlet实例,但是对于不同的子应用分别能有自己的RequestProcessor实例每个RequestProcessor实例分别对应不同的struts配置文件。
??? 子应用的ProcessorClass类必须重写一般就是继承RequestProcessor类，然后再其配置文件的controller元素中的<processorClass>属性中作出修改。那么当
?? getRequestProcessor(getModuleConfig(request)).process(request,response); 就能根据request选择相应的moduleconfig,再根据其<processorClass>属性选择相应的 RequestProcessor子类来处理相应的请求了。
