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spring有三種啟動(dòng)方式,使用ContextLoaderServlet,ContextLoaderListener和ContextLoaderPlugIn.
看一下ContextLoaderListener的源碼,這是一個(gè)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的源碼
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,這里面放了WebApplicationContext,需要使用時(shí)從ServletContext取出
可以使用WebApplicationContextUtils得到WebApplicationContext
public static WebApplicationContext getWebApplicationContext(ServletContext sc) {
Object attr = sc.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
if (attr == null) {
return null;
}
if (attr instanceof RuntimeException) {
throw (RuntimeException) attr;
}
if (attr instanceof Error) {
throw (Error) attr;
}
if (!(attr instanceof WebApplicationContext)) {
throw new IllegalStateException("Root context attribute is not of type WebApplicationContext: " + attr);
}
return (WebApplicationContext) attr;
}
關(guān)鍵的問題在于struts如何啟動(dòng)的spring的,ContextLoaderPlugIn的源碼

// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);

public String getServletContextAttributeName() {
return SERVLET_CONTEXT_PREFIX + getModulePrefix();
}
不同加載的Key竟然不同,原因就是WebApplicationContext放在那里的問題,可spring調(diào)用的時(shí)候會(huì)根據(jù)WebApplicationContext里面定義的那個(gè)名字去找的,問題出在這里


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>


原理是這樣的,Struts雖然只能有一個(gè)ActionServlet實(shí)例,但是對(duì)于不同的子應(yīng)用分別能有自己的RequestProcessor實(shí)例每個(gè)RequestProcessor實(shí)例分別對(duì)應(yīng)不同的struts配置文件。
子應(yīng)用的ProcessorClass類必須重寫一般就是繼承RequestProcessor類，然后再其配置文件的controller元素中的<processorClass>屬性中作出修改。那么當(dāng)
getRequestProcessor(getModuleConfig(request)).process(request,response);就能根據(jù)request選擇相應(yīng)的moduleconfig,再根據(jù)其<processorClass>屬性選擇相應(yīng)的RequestProcessor子類來處理相應(yīng)的請(qǐng)求了。  回復(fù)  更多評(píng)論