tomcat源码学习--轰炸机core（一）
前言：
catalina下面的core包，包含了很多我们平时一直使用到的东西，以前一直用不知道原理，也只知道j2EE api里面的东西，在tomcat下写了这么久得程序，一直疑惑它到底是怎么做到的，下面就可以好好看看了。
首先application，实现javax.servlet Interface ServletContext
In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won't be truly global). Use an external resource like a database instead.
The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.
这家伙很重要，那么每个容器必须自己实现他的规则，tomcat如何实现呢？
eclipse果断查找
ApplicationContextFacade是为ApplicationContext服务的一个类，ApplicationContext才是标准实现了这个借口的类，至于JspCServletContext是Simple ServletContext
那么就重点看ApplicationContext，有的属性如下
构造方法如下：
public void setAttribute(String name, Object value) { // Name cannot be null if (name == null) throw new IllegalArgumentException (sm.getString("applicationContext.setAttribute.namenull")); // Null value is the same as removeAttribute() if (value == null) { removeAttribute(name); return; } Object oldValue = null; boolean replaced = false; // Add or replace the specified attribute // Check for read only attribute if (readOnlyAttributes.containsKey(name)) return; oldValue = attributes.get(name); if (oldValue != null) replaced = true; attributes.put(name, value); // Notify interested application event listeners Object listeners[] = context.getApplicationEventListeners(); if ((listeners == null) || (listeners.length == 0)) return; ServletContextAttributeEvent event = null; if (replaced) event = new ServletContextAttributeEvent(context.getServletContext(), name, oldValue); else event = new ServletContextAttributeEvent(context.getServletContext(), name, value); for (int i = 0; i < listeners.length; i++) { if (!(listeners[i] instanceof ServletContextAttributeListener)) continue; ServletContextAttributeListener listener = (ServletContextAttributeListener) listeners[i]; try { if (replaced) { context.fireContainerEvent ("beforeContextAttributeReplaced", listener); listener.attributeReplaced(event); context.fireContainerEvent("afterContextAttributeReplaced", listener); } else { context.fireContainerEvent("beforeContextAttributeAdded", listener); listener.attributeAdded(event); context.fireContainerEvent("afterContextAttributeAdded", listener); } } catch (Throwable t) { if (replaced) context.fireContainerEvent("afterContextAttributeReplaced", listener); else context.fireContainerEvent("afterContextAttributeAdded", listener); // FIXME - should we do anything besides log these? log(sm.getString("applicationContext.attributeEvent"), t); } } }
容器里面使用的是哪一个呢？我们并不知道，我们完全是面对借口来编程，遵循j2ee api规范，然后具体的方法具体的容器有自己的实现。
同样下面还有req reps，分别有两个实现，比如继承自HttpServletRequestWrapper或者ServletRequestWrapper的两个类，还来了句这个，顶层都是ServletRequest
/** * Return the session associated with this Request, creating one * if necessary. */ public HttpSession getSession() { return (getSession(true)); } /** * Return the session associated with this Request, creating one * if necessary and requested. * * @param create Create a new session if one does not exist */ public HttpSession getSession(boolean create) { if (crossContext) { // There cannot be a session if no context has been assigned yet if (context == null) return (null); // Return the current session if it exists and is valid if (session != null && session.isValid()) { return (session.getSession()); } HttpSession other = super.getSession(false); if (create && (other == null)) { // First create a session in the first context: the problem is // that the top level request is the only one which can // create the cookie safely other = super.getSession(true); } if (other != null) { Session localSession = null; try { localSession = context.getManager().findSession(other.getId()); if (localSession != null && !localSession.isValid()) { localSession = null; } } catch (IOException e) { // Ignore } if (localSession == null && create) { localSession = context.getManager().createSession(other.getId()); } if (localSession != null) { localSession.access(); session = localSession; return session.getSession(); } } return null; } else { return super.getSession(create); } }
ps：好累啊，看不动了，下次重点看下面的几个复杂的容器类ContainerBase Lifecycle
