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Lifecycle-生命周期

Lifecycle-生命周期

作者: stayiwithime | 来源:发表于2021-03-23 14:22 被阅读0次

官方接口文档：http://tomcat.apache.org/tomcat-9.0-doc/api/org/apache/catalina/Lifecycle.html

生命周期流转图

类图

生命周期

plantUML

@startuml
interface Lifecycle{
    + String BEFORE_INIT_EVENT = "before_init"
    + String AFTER_INIT_EVENT = "after_init"
    + String START_EVENT = "start"
    + String BEFORE_START_EVENT = "before_start"
    + String AFTER_START_EVENT = "after_start"
    + String STOP_EVENT = "stop"
    + String BEFORE_STOP_EVENT = "before_stop"
    + String AFTER_STOP_EVENT = "after_stop"
    + String AFTER_DESTROY_EVENT = "after_destroy"
    + String BEFORE_DESTROY_EVENT = "before_destroy"
    + String PERIODIC_EVENT = "periodic"
    + String CONFIGURE_START_EVENT = "configure_start"
    + String CONFIGURE_STOP_EVENT = "configure_stop"
    + void addLifecycleListener(LifecycleListener listener)
    + LifecycleListener[] findLifecycleListeners()
    + void removeLifecycleListener(LifecycleListener listener)
    + void init() throws LifecycleException
    + void start() throws LifecycleException
    + void stop() throws LifecycleException
    + void destroy() throws LifecycleException
    + LifecycleState getState()
    + String getStateName()
    + interface SingleUse {}
}

interface LifecycleListener{
    + lifecycleEvent(LifecycleEvent event)
}

Lifecycle .> LifecycleListener

class LifecycleEvent{
    + LifecycleEvent(Lifecycle lifecycle, String type, Object data)
    - final Object data
    - final String type
    + Object getData()
    + Lifecycle getLifecycle()
    + String getType()
}

LifecycleListener .> LifecycleEvent
LifecycleEvent --> Lifecycle

enum LifecycleState{
    NEW(false, null),
        INITIALIZING(false, Lifecycle.BEFORE_INIT_EVENT),
        INITIALIZED(false, Lifecycle.AFTER_INIT_EVENT),
        STARTING_PREP(false, Lifecycle.BEFORE_START_EVENT),
        STARTING(true, Lifecycle.START_EVENT),
        STARTED(true, Lifecycle.AFTER_START_EVENT),
        STOPPING_PREP(true, Lifecycle.BEFORE_STOP_EVENT),
        STOPPING(false, Lifecycle.STOP_EVENT),
        STOPPED(false, Lifecycle.AFTER_STOP_EVENT),
        DESTROYING(false, Lifecycle.BEFORE_DESTROY_EVENT),
        DESTROYED(false, Lifecycle.AFTER_DESTROY_EVENT),
        FAILED(false, null);
}
Lifecycle .> LifecycleState

@enduml

Lifecycle

生命周期接口：

  • 内部定义了Lifecycle.SingleUse接口:标识接口，实现该接口的实例在使用一次后就会被销毁
 @Override
    public final synchronized void stop() throws LifecycleException {

        ...
        try {
            ...
        } catch (Throwable t) {
            handleSubClassException(t, "lifecycleBase.stopFail", toString());
        } finally {
            if (this instanceof Lifecycle.SingleUse) {
                // Complete stop process first
                setStateInternal(LifecycleState.STOPPED, null, false);
                destroy();
            }
        }
    }

LifecycleBase

生命周期接口基本实现

源码阅读

    private static final Log log = LogFactory.getLog(LifecycleBase.class);
    private static final StringManager sm = StringManager.getManager(LifecycleBase.class);
    private final List<LifecycleListener> lifecycleListeners = new CopyOnWriteArrayList<>();
    private volatile LifecycleState state = LifecycleState.NEW;
    private boolean throwOnFailure = true;
    public boolean getThrowOnFailure() {
        return throwOnFailure;
    }
    public void setThrowOnFailure(boolean throwOnFailure) {
        this.throwOnFailure = throwOnFailure;
    }
   @Override
    public void addLifecycleListener(LifecycleListener listener) {
        lifecycleListeners.add(listener);
    }
   @Override
    public LifecycleListener[] findLifecycleListeners() {
        return lifecycleListeners.toArray(new LifecycleListener[0]);
    }
    @Override
    public void removeLifecycleListener(LifecycleListener listener) {
        lifecycleListeners.remove(listener);
    }
   protected void fireLifecycleEvent(String type, Object data) {
        LifecycleEvent event = new LifecycleEvent(this, type, data);
        for (LifecycleListener listener : lifecycleListeners) {
            listener.lifecycleEvent(event);
        }
    }
  • log：日志打印
  • StringManager : 这个类可以看具体实现，用了单例模式，是针对每个包生成一个单例，用来管理ResourceBundle，根据各个包相关的提示信息等
  • lifecycleListeners ：监听器，线程安全的list
  • state ：实例的当前状态（或是说生命周期的那个阶段）
  • throwOnFailure ：钩子方法的值，由子类来设置是否需要在错误的时候抛异常
  • 以及几个监听器管理相关的方法
@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) {
            handleSubClassException(t, "lifecycleBase.initFail", toString());
        }
    }
  protected abstract void initInternal() throws LifecycleException;

  • init(): 使用了模板方法模式，init给出了初始化的基本步骤

    1. final ：不能被子类复写
    2. synchronized ：线程安全
    3. 检查前置状态是否正确（LifecycleState.NEW），错误就会抛出异常
    4. 设置为LifecycleState.INITIALIZING，并执行监听器（before_init）
    5. 执行子类实现的初始化方法initInternal()
    6. 设置为LifecycleState.INITIALIZED，并执行监听器（after_init）
    7. 4,5,6执行过程失败，将设置为LifecycleState.FAILED， 由throwOnFailure 控制是否抛异常

  • initInternal()：初始化具体的实现由子类提供

 @Override
    public final synchronized void start() throws LifecycleException {

        if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||
                LifecycleState.STARTED.equals(state)) {

            if (log.isDebugEnabled()) {
                Exception e = new LifecycleException();
                log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);
            } else if (log.isInfoEnabled()) {
                log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));
            }

            return;
        }

        if (state.equals(LifecycleState.NEW)) {
            init();
        } else if (state.equals(LifecycleState.FAILED)) {
            stop();
        } else if (!state.equals(LifecycleState.INITIALIZED) &&
                !state.equals(LifecycleState.STOPPED)) {
            invalidTransition(Lifecycle.BEFORE_START_EVENT);
        }

        try {
            setStateInternal(LifecycleState.STARTING_PREP, null, false);
            startInternal();
            if (state.equals(LifecycleState.FAILED)) {
                stop();
            } else if (!state.equals(LifecycleState.STARTING)) {
                invalidTransition(Lifecycle.AFTER_START_EVENT);
            } else {
                setStateInternal(LifecycleState.STARTED, null, false);
            }
        } catch (Throwable t) {
            handleSubClassException(t, "lifecycleBase.startFail", toString());
        }
    }
    protected abstract void startInternal() throws LifecycleException;
  • start(): 使用了模板方法模式
    1. final ：不能被子类复写
    2. synchronized ：线程安全
    3. 前置状态检查（LifecycleState.STARTING_PREP，LifecycleState.STARTING，LifecycleState.STARTED）属于前置状态错误，输出相关日志并结束调用
    4. 前置状态是LifecycleState.NEW，就先init()初始化
    5. 前置状态是LifecycleState.FAILED，就先stop()
    6. 前置状态不是LifecycleState.INITIALIZED或LifecycleState.STOPPED，会抛出异常
    7. 设置为LifecycleState.STARTING_PREP，并执行监听器（before_start）
    8. startInternal()：子类实现需要把状态置为LifecycleState.STARTING，执行失败可能需要置为LifecycleState.FAILED
    9. 如果状态为LifecycleState.FAILED，会调用stop()
    10. 如果状态不为LifecycleState.STARTING，会抛异常
    11. 执行成功，设置为LifecycleState.STARTED，并执行监听器（after_start）
    12. 7,8,9,10,11执行过程失败，将设置为LifecycleState.FAILED， 由throwOnFailure 控制是否抛异常
  • startInternal():start的具体实现
 @Override
    public final synchronized void stop() throws LifecycleException {

        if (LifecycleState.STOPPING_PREP.equals(state) || LifecycleState.STOPPING.equals(state) ||
                LifecycleState.STOPPED.equals(state)) {

            if (log.isDebugEnabled()) {
                Exception e = new LifecycleException();
                log.debug(sm.getString("lifecycleBase.alreadyStopped", toString()), e);
            } else if (log.isInfoEnabled()) {
                log.info(sm.getString("lifecycleBase.alreadyStopped", toString()));
            }

            return;
        }

        if (state.equals(LifecycleState.NEW)) {
            state = LifecycleState.STOPPED;
            return;
        }

        if (!state.equals(LifecycleState.STARTED) && !state.equals(LifecycleState.FAILED)) {
            invalidTransition(Lifecycle.BEFORE_STOP_EVENT);
        }

        try {
            if (state.equals(LifecycleState.FAILED)) {
                fireLifecycleEvent(BEFORE_STOP_EVENT, null);
            } else {
                setStateInternal(LifecycleState.STOPPING_PREP, null, false);
            }
            stopInternal();

            if (!state.equals(LifecycleState.STOPPING) && !state.equals(LifecycleState.FAILED)) {
                invalidTransition(Lifecycle.AFTER_STOP_EVENT);
            }

            setStateInternal(LifecycleState.STOPPED, null, false);
        } catch (Throwable t) {
            handleSubClassException(t, "lifecycleBase.stopFail", toString());
        } finally {
            if (this instanceof Lifecycle.SingleUse) {
                setStateInternal(LifecycleState.STOPPED, null, false);
                destroy();
            }
        }
    }

    protected abstract void stopInternal() throws LifecycleException;

  • stop(): 使用了模板方法模式

    1. final ：不能被子类复写
    2. synchronized ：线程安全
    3. 前置状态检查(LifecycleState.STOPPING_PREP,LifecycleState.STOPPING,LifecycleState.STOPPED)前置状态错误，输出相关日志并结束调用
    4. 前置状态为LifecycleState.NEW，直接修改状态为LifecycleState.STOPPED
    5. 前置状态不为LifecycleState.STARTED和LifecycleState.FAILED，抛出异常
    6. 前置状态为LifecycleState.FAILED，直接先执行监听器（before_stop）
    7. 前置状态为LifecycleState.STARTED，设置状态为LifecycleState.STOPPING_PREP并执行监听器（before_stop）
    8. stopInternal()：需要将状态置为LifecycleState.STOPPING或LifecycleState.FAILED
    9. 如果 stopInternal()设置的状态不正确就抛异常
    10. 设置状态为LifecycleState.STOPPED，并执行监听器（after_stop）
    11. 6,7,8,9,10 可能抛异常
    12. 如果之类实现了Lifecycle.SingleUse接口，会执行destroy()

  • stopInternal():子类具体实现

 @Override
    public final synchronized void destroy() throws LifecycleException {
        if (LifecycleState.FAILED.equals(state)) {
            try {            
                stop();
            } catch (LifecycleException e) {             
                log.error(sm.getString("lifecycleBase.destroyStopFail", toString()), e);
            }
        }
        if (LifecycleState.DESTROYING.equals(state) || LifecycleState.DESTROYED.equals(state)) {
            if (log.isDebugEnabled()) {
                Exception e = new LifecycleException();
                log.debug(sm.getString("lifecycleBase.alreadyDestroyed", toString()), e);
            } else if (log.isInfoEnabled() && !(this instanceof Lifecycle.SingleUse)) {          
                log.info(sm.getString("lifecycleBase.alreadyDestroyed", toString()));
            }
            return;
        }

        if (!state.equals(LifecycleState.STOPPED) && !state.equals(LifecycleState.FAILED) &&
                !state.equals(LifecycleState.NEW) && !state.equals(LifecycleState.INITIALIZED)) {
            invalidTransition(Lifecycle.BEFORE_DESTROY_EVENT);
        }

        try {
            setStateInternal(LifecycleState.DESTROYING, null, false);
            destroyInternal();
            setStateInternal(LifecycleState.DESTROYED, null, false);
        } catch (Throwable t) {
            handleSubClassException(t, "lifecycleBase.destroyFail", toString());
        }
    }

    protected abstract void destroyInternal() throws LifecycleException;

  • destroy(): 模板方法模式

    1. final ：不能被子类复写
    2. synchronized ：线程安全
    3. 前置状态为LifecycleState.FAILED，先执行stop()
    4. 前置状态为LifecycleState.DESTROYING或LifecycleState.DESTROYED，打印日志，结束调用
    5. 前置状态不为LifecycleState.STOPPED，LifecycleState.FAILED，LifecycleState.NEW，LifecycleState.INITIALIZED，抛出异常
    6. 设置状态为LifecycleState.DESTROYING 并执行监听器（before_destory）
    7. destroyInternal()
    8. 设置状态为LifecycleState.DESTROYED 并执行监听器 （after_destory）
    9. 6,7,8 可能抛异常

  • destroyInternal()：子类实现具体的销毁方法

    @Override
    public LifecycleState getState() {
        return state;
    }

    @Override
    public String getStateName() {
        return getState().toString();
    }

    protected synchronized void setState(LifecycleState state) throws LifecycleException {
        setStateInternal(state, null, true);
    }

    protected synchronized void setState(LifecycleState state, Object data)
            throws LifecycleException {
        setStateInternal(state, data, true);
    }


    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) {     
            if (state == null) {
                invalidTransition("null");  
                return;
            } 
            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))) { 
                invalidTransition(state.name());
            }
        }
        this.state = state;
        String lifecycleEvent = state.getLifecycleEvent();
        if (lifecycleEvent != null) {
            fireLifecycleEvent(lifecycleEvent, data);
        }
    }

    private void invalidTransition(String type) throws LifecycleException {
        String msg = sm.getString("lifecycleBase.invalidTransition", type, toString(), state);
        throw new LifecycleException(msg);
    }

    private void handleSubClassException(Throwable t, String key, Object... args) throws LifecycleException {
        setStateInternal(LifecycleState.FAILED, null, false);
        ExceptionUtils.handleThrowable(t);
        String msg = sm.getString(key, args);
        if (getThrowOnFailure()) {
            if (!(t instanceof LifecycleException)) {
                t = new LifecycleException(msg, t);
            }
            throw (LifecycleException) t;
        } else {
            log.error(msg, t);
        }
    }
  • setState(): 具体细节是setStateInternal（）为子类提供的设置状态的方法，且必须检查对应的状态是否正确

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