/**
* Add a LifecycleEvent listener to this component.
*
* @param listener The listener to add
*/
public void addLifecycleListener(LifecycleListener listener);//给该组将添加一个监听器
/**
* Get the life cycle listeners associated with this life cycle. If this
* component has no listeners registered, a zero-length array is returned.
*/
public LifecycleListener[] findLifecycleListeners();//获取该组件所有已注册的监听器
/**
* Remove a LifecycleEvent listener from this component.
*
* @param listener The listener to remove
*/
public void removeLifecycleListener(LifecycleListener listener);//删除该组件中的一个监听器
LifecycleListener接口
public interface LifecycleListener {
/**
* Acknowledge the occurrence of the specified event.
*
* @param event LifecycleEvent that has occurred
*/
public void lifecycleEvent(LifecycleEvent event);
}
LifecycleEvent接口（继承jdk 内置的 java.util.EventObject）
public final class LifecycleEvent extends EventObject {
private static final long serialVersionUID = 1L;
// ----------------------------------------------------------- Constructors
/**
* Construct a new LifecycleEvent with the specified parameters.
*
* @param lifecycle Component on which this event occurred
* @param type Event type (required)
* @param data Event data (if any)
*/
public LifecycleEvent(Lifecycle lifecycle, String type, Object data) {
super(lifecycle);
this.type = type;
this.data = data;
}
// ----------------------------------------------------- Instance Variables
/**
* The event data associated with this event.
*/
private final Object data;
/**
* The event type this instance represents.
*/
private final String type;
// ------------------------------------------------------------- Properties
/**
* Return the event data of this event.
*/
public Object getData() {
return (this.data);
}
/**
* Return the Lifecycle on which this event occurred.
*/
public Lifecycle getLifecycle() {
return (Lifecycle) getSource();
}
/**
* Return the event type of this event.
*/
public String getType() {
return (this.type);
}
}
在 LifecycleBase类里LifecycleSupport是这么初始化的：private final LifecycleSupport lifecycle = new LifecycleSupport(this);，就是把StandardServer(LifecycleBase)的实例作为Lifecycle
public void fireLifecycleEvent(String type, Object data) {
LifecycleEvent event = new LifecycleEvent(lifecycle, type, data);
LifecycleListener interested[] = listeners;
for (int i = 0; i < interested.length; i++)
interested[i].lifecycleEvent(event);
}
digester.addObjectCreate("Server/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Listener");
digester.addSetNext("Server/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
LifecycleSupport
public void addLifecycleListener(LifecycleListener listener) {
synchronized (listenersLock) {
LifecycleListener results[] =
new LifecycleListener[listeners.length + 1];
for (int i = 0; i < listeners.length; i++)
results[i] = listeners[i];
results[listeners.length] = listener;
listeners = results;
}
}
private LifecycleListener listeners[] = new LifecycleListener[0];
Lifecycle接口
LifecycleListener接口
LifecycleEvent接口（继承jdk 内置的 java.util.EventObject）
LifecycleSupport的fireLifecycleEvent，向注册到组件中的所有监听器发布这个新构造的事件对象。
在 LifecycleBase类里LifecycleSupport是这么初始化的：
private final LifecycleSupport lifecycle = new LifecycleSupport(this);，就是把StandardServer(LifecycleBase)的实例作为Lifecycleorg.apache.catalina.startup.Catalina 类的 createStartDigester 方法有这么一段代码：
LifecycleSupport
如果对设计模式比较熟悉的话会发现 Tomcat 的 Lifecycle 使用的是观察者模式：LifecycleListener 代表的是抽象观察者，它定义一个 lifecycleEvent 方法，而实现该接口的监听器是作为具体的观察者。Lifecycle 接口代表的是抽象主题，它定义了管理观察者的方法和它要所做的其它方法。而各组件代表的是具体主题，它实现了抽象主题的所有方法。通常会由具体主题保存对具体观察者对象有用的内部状态；在这种内部状态改变时给其观察者发出一个通知。Tomcat 对这种模式做了改进，增加了另外两个工具类：LifecycleSupport、LifecycleEvent ，它们作为辅助类扩展了观察者的功能。LifecycleEvent 中定义了事件类别，不同的事件在具体观察者中可区别处理，更加灵活。LifecycleSupport 类代理了所有具体主题对观察者的管理，将这个管理抽出来统一实现，以后如果修改只要修改 LifecycleSupport 类就可以了，不需要去修改所有具体主题，因为所有具体主题的对观察者的操作都被代理给 LifecycleSupport 类了。 事件的发布使用的是推模式，即每发布一个事件都会通知主题的所有具体观察者，由各观察者再来决定是否需要对该事件进行后续处理。