Tomcat Lifecycle

org.apache.catalina.Lifecycle 接口统一管理生命周期，所有生命周期组件都要实现Lifecycle接口。

该接口定义了13个String类型的常量，用于LifecycleEvent时间的type属性，作用是区分组件发出的LifecycleEvent事件时的状态，

这种设计方式可以让多中状态都发送同一种类型的时间，然后用其中的一个属性来区分状态，而不用定义多种事件。

 public interface Lifecycle {

     public static final String BEFORE_INIT_EVENT = "before_init";
     public static final String AFTER_INIT_EVENT = "after_init";
     public static final String START_EVENT = "start";
     public static final String BEFORE_START_EVENT = "before_start";
     public static final String AFTER_START_EVENT = "after_start";
     public static final String STOP_EVENT = "stop";
     public static final String BEFORE_STOP_EVENT = "before_stop";
     public static final String AFTER_STOP_EVENT = "after_stop";
     public static final String AFTER_DESTROY_EVENT = "after_destroy";
     public static final String BEFORE_DESTROY_EVENT = "before_destroy";
     public static final String PERIODIC_EVENT = "periodic";
     public static final String CONFIGURE_START_EVENT = "configure_start";
     public static final String CONFIGURE_STOP_EVENT = "configure_stop";

     public void addLifecycleListener(LifecycleListener listener);

     public LifecycleListener[] findLifecycleListeners();

     public void removeLifecycleListener(LifecycleListener listener);

     public void init() throws LifecycleException;

     public void start() throws LifecycleException;

     public void stop() throws LifecycleException;

     public void destroy() throws LifecycleException;

     public LifecycleState getState();

     public String getStateName();

     public interface SingleUse {
     }
 }