标签：tomcat digester web应用 栈 servlet
在这一节里我们说说ContextConfig这个类。 LifecycleListener listener = new ContextConfig();
((Lifecycle) context).addLifecycleListener(listener); 首先得在StandContext里注入ContextConfig这个监听器。ContextConfig.java
public void lifecycleEvent(LifecycleEvent event) {
...
// Process the event that has occurred
if (event.getType().equals(Lifecycle.START_EVENT))
start();
else if (event.getType().equals(Lifecycle.STOP_EVENT))
stop();
}我们看看ContextConfig的start方法。 private synchronized void start() {
...
// Process the default and application web.xml files
defaultConfig(); //解析conf/xml.xml
applicationConfig(); //解析WEB-INF/web.xml
...
}我们先不管整个tomcat的xml就看单个项目的: private void applicationConfig() {
...
// Process the application web.xml file
synchronized (webDigester) {
//public static final String ApplicationWebXml = "/WEB-INF/web.xml";
URL url =servletContext.getResource(Constants.ApplicationWebXml);
InputSource is = new InputSource(url.toExternalForm());
is.setByteStream(stream);
webDigester.setDebug(getDebug());
if (context instanceof StandardContext) {
((StandardContext) context).setReplaceWelcomeFiles(true);
}
webDigester.clear();
webDigester.push(context);//此时的栈里面就有context了
webDigester.parse(is); //开始解析
}
...
}现在的问题是,那webDigester是怎么来的? private static Digester createWebDigester() {
...
Digester webDigester = new Digester();
...
webDigester.addRuleSet(new WebRuleSet()); //addRuleSet 对这个不清楚的看上一节
return (webDigester);
} 现在我们就要去看WebRuleSet类了,还记得主要看哪个方法吗?WebRuleSet.java
public void addRuleInstances(Digester digester) {
....
digester.addRule(prefix + "web-app/servlet",new WrapperCreateRule(digester));
...
digester.addCallMethod(prefix + "web-app/servlet/servlet-class",
"setServletClass", 0);
digester.addCallMethod(prefix + "web-app/servlet/servlet-name",
"setName", 0);
digester.addCallMethod(prefix + "web-app/servlet-mapping",
"addServletMapping", 2);
//setServletClass这个方法最后在哪里调用的? 请大家自己想一想
}
final class WrapperCreateRule extends Rule {
public void begin(Attributes attributes) throws Exception {
Context context =(Context) digester.peek(digester.getCount() - 1);
Wrapper wrapper = context.createWrapper();
digester.push(wrapper);
if (digester.getDebug() > 0)
digester.log("new " + wrapper.getClass().getName());
}
}web-app/servlet/servlet-name 碰到这个后,调用wrapper的那个方法就ok。
How tomcat works 读书笔记十五 Digester库 下
标签：tomcat digester web应用 栈 servlet
原文地址：http://blog.csdn.net/dlf123321/article/details/41895231
