tomcat-生命周期

Server,Service,Engine,Host,Context都实现了Lifecycle接口，通过这个接口管理了这些核心组件的生命周期；

使用事件监听模式，当状态发生改变时，同步给不同的组件；

LifecycleBase

LifecycleBase是使用了状态机+模板模式来实现的

// 初始化方法
protected abstract void initInternal() throws LifecycleException;
// 启动方法
protected abstract void startInternal() throws LifecycleException;
// 停止方法
protected abstract void stopInternal() throws LifecycleException;
// 销毁方法
protected abstract void destroyInternal() throws LifecycleException;
​

#init

/*
 * 1. 模版设计方式
 */
@Override
public final synchronized void init() throws LifecycleException {
    if (!state.equals(LifecycleState.NEW)) {
        invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
    }
​
    try {
        setStateInternal(LifecycleState.INITIALIZING, null, false);
        initInternal();
        setStateInternal(LifecycleState.INITIALIZED, null, false);
    } catch (Throwable t) {
        ExceptionUtils.handleThrowable(t);
        setStateInternal(LifecycleState.FAILED, null, false);
        throw new LifecycleException(
                sm.getString("lifecycleBase.initFail",toString()), t);
    }
}
​
# initInternal留给子类进行实现的类
protected abstract void initInternal() throws LifecycleException;
​
/*
 * 1. 设置state状态
 * 2. 触发状态变更事件
 */
private synchronized void setStateInternal(LifecycleState state,
            Object data, boolean check) throws LifecycleException {
​
        if (log.isDebugEnabled()) {
            log.debug(sm.getString("lifecycleBase.setState", this, state));
        }
​
        if (check) {
            // Must have been triggered by one of the abstract methods (assume
            // code in this class is correct)
            // null is never a valid state
            if (state == null) {
                invalidTransition("null");
                // Unreachable code - here to stop eclipse complaining about
                // a possible NPE further down the method
                return;
            }
​
            // Any method can transition to failed
            // startInternal() permits STARTING_PREP to STARTING
            // stopInternal() permits STOPPING_PREP to STOPPING and FAILED to
            // STOPPING
            if (!(state == LifecycleState.FAILED ||
                    (this.state == LifecycleState.STARTING_PREP &&
                            state == LifecycleState.STARTING) ||
                    (this.state == LifecycleState.STOPPING_PREP &&
                            state == LifecycleState.STOPPING) ||
                    (this.state == LifecycleState.FAILED &&
                            state == LifecycleState.STOPPING))) {
                // No other transition permitted
                invalidTransition(state.name());
            }
        }
​
        this.state = state;
        String lifecycleEvent = state.getLifecycleEvent();
        if (lifecycleEvent != null) {
            fireLifecycleEvent(lifecycleEvent, data);
        }
    }