浅读tomcat架构设计之tomcat生命周期(2)
浅读tomcat架构设计和tomcat启动过程(1)
https://www.cnblogs.com/piaomiaohongchen/p/14977272.html
tomcat通过org.apache.catalina.Lifecycle接口统一管理生命周期,所有有生命周期的组建都要实现Lifecycle接口.
通过反射加载查看代码:
Lifecycle的接口方法有很多,简单解读下:
(1)定义13个String类型的常量,不同的常量,代表不同的状态信息
(2)定义了3个管理监听器的方法:
分别是添加,监听和删除
void addLifecycleListener(LifecycleListener var1); LifecycleListener[] findLifecycleListeners(); void removeLifecycleListener(LifecycleListener var1);
(3)定义了四个生命周期方法:
分别是初始化,开启,停止,销毁:
void init() throws LifecycleException; void start() throws LifecycleException; void stop() throws LifecycleException; void destroy() throws LifecycleException;
(4)定义了获取状态的两个方法:
LifecycleState getState();
String getStateName();
其中getState的返回类是enum类型,getStateName返回的类型是String类型
Lifecycle接口的默认实现是org.apache.catalina.util.LifecycleBase,LifecycleBase为Lifecycle里的接口方法提供了默认实现.
先看看三个管理监听器方法的具体实现:
org.apache.catalina.util.LifecycleBase:
public void addLifecycleListener(LifecycleListener listener) { this.lifecycle.addLifecycleListener(listener); } public LifecycleListener[] findLifecycleListeners() { return this.lifecycle.findLifecycleListeners(); } public void removeLifecycleListener(LifecycleListener listener) { this.lifecycle.removeLifecycleListener(listener); }
发现在方法内部都是调用的lifecycle.**()方法
而this.lifecycle的定义是
private final LifecycleSupport lifecycle = new LifecycleSupport(this);
三个监听器方法都是调用的是LifecycleSupport类的对象方法
LifecycleSupport监听器是通过一个数组属性listeners来保存的,代码如下:
org.apache.catalina.util.LifecycleSupport:
private final Object listenersLock = new Object(); public LifecycleSupport(Lifecycle lifecycle) { this.lifecycle = lifecycle; } public void addLifecycleListener(LifecycleListener listener) { synchronized(this.listenersLock) { LifecycleListener[] results = new LifecycleListener[this.listeners.length + 1]; for(int i = 0; i < this.listeners.length; ++i) { results[i] = this.listeners[i]; } results[this.listeners.length] = listener; this.listeners = results; } } public LifecycleListener[] findLifecycleListeners() { return this.listeners; } public void fireLifecycleEvent(String type, Object data) { LifecycleEvent event = new LifecycleEvent(this.lifecycle, type, data); LifecycleListener[] interested = this.listeners; for(int i = 0; i < interested.length; ++i) { interested[i].lifecycleEvent(event); } } public void removeLifecycleListener(LifecycleListener listener) { synchronized(this.listenersLock) { int n = -1; for(int i = 0; i < this.listeners.length; ++i) { if (this.listeners[i] == listener) { n = i; break; } } if (n >= 0) { LifecycleListener[] results = new LifecycleListener[this.listeners.length - 1]; int j = 0; for(int i = 0; i < this.listeners.length; ++i) { if (i != n) { results[j++] = this.listeners[i]; } } this.listeners = results; } } }
这三个方法的实现非常简单,就是新增/删除/查找等动作的实现,就是对listener属性做操作
其中的fireLifecycleEvent函数的含义是用于遍历所有监听器进行处理
四个生命周期的方法:
先看init方法,让我们回到之前的org.apache.catalina.util.LifecycleBase类:
org.apache.catalina.util.LifecycleBase:
public final synchronized void init() throws LifecycleException { if (!this.state.equals(LifecycleState.NEW)) { this.invalidTransition("before_init"); } this.setStateInternal(LifecycleState.INITIALIZING, (Object)null, false); try { this.initInternal(); } catch (Throwable var2) { ExceptionUtils.handleThrowable(var2); this.setStateInternal(LifecycleState.FAILED, (Object)null, false); throw new LifecycleException(sm.getString("lifecycleBase.initFail", new Object[]{this.toString()}), var2); } this.setStateInternal(LifecycleState.INITIALIZED, (Object)null, false); }
代码很简单,就是先判断state是否是LifecycleState.NEW,如果是NEW的话就设置为state状态为LifecycleState.INITIALIZING,如果不是,就抛出异常,所以init初始化的时候必须是LifecycleState.NEW
接着往下看,看start方法:
public final synchronized void start() throws LifecycleException { if (!LifecycleState.STARTING_PREP.equals(this.state) && !LifecycleState.STARTING.equals(this.state) && !LifecycleState.STARTED.equals(this.state)) { if (this.state.equals(LifecycleState.NEW)) { this.init(); } else if (this.state.equals(LifecycleState.FAILED)) { this.stop(); } else if (!this.state.equals(LifecycleState.INITIALIZED) && !this.state.equals(LifecycleState.STOPPED)) { this.invalidTransition("before_start"); } this.setStateInternal(LifecycleState.STARTING_PREP, (Object)null, false); try { this.startInternal(); } catch (Throwable var2) { ExceptionUtils.handleThrowable(var2); this.setStateInternal(LifecycleState.FAILED, (Object)null, false); throw new LifecycleException(sm.getString("lifecycleBase.startFail", new Object[]{this.toString()}), var2); } if (!this.state.equals(LifecycleState.FAILED) && !this.state.equals(LifecycleState.MUST_STOP)) { if (!this.state.equals(LifecycleState.STARTING)) { this.invalidTransition("after_start"); } this.setStateInternal(LifecycleState.STARTED, (Object)null, false); } else { this.stop(); } } else { if (log.isDebugEnabled()) { Exception e = new LifecycleException(); log.debug(sm.getString("lifecycleBase.alreadyStarted", new Object[]{this.toString()}), e); } else if (log.isInfoEnabled()) { log.info(sm.getString("lifecycleBase.alreadyStarted", new Object[]{this.toString()})); } } }
start方法做的事情比int方法多一些,判断state状态,如果是LifecycleState.NEW,就初始化,根据不同的state状态,进不同的逻辑,然后设置状态调用setStateInternal方法:
跟进方法:
还是在org.apache.catalina.util.LifecycleBase:
private synchronized void setStateInternal(LifecycleState state, Object data, boolean check) throws LifecycleException { if (log.isDebugEnabled()) { log.debug(sm.getString("lifecycleBase.setState", new Object[]{this, state})); } if (check) { if (state == null) { this.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)) { this.invalidTransition(state.name()); } } this.state = state; String lifecycleEvent = state.getLifecycleEvent(); if (lifecycleEvent != null) { this.fireLifecycleEvent(lifecycleEvent, data); } }
这个方法先是判断check,然后判断state是否为null,是null就抛出异常,最后将state赋值给state变量,然后调用getLifecycleEvent方法处理事件,下面的this.fireLifecycleEvent(lifecycleEvent, data);实际上调用的是LifecycleSupport类的方法:
跟进这个方法看下:
protected void fireLifecycleEvent(String type, Object data) { this.lifecycle.fireLifecycleEvent(type, data); }
继续往上回溯:
private final LifecycleSupport lifecycle = new LifecycleSupport(this);
同理stop和destroy方法逻辑类似
获取状态的两个方法
还是在org.apache.catlina.util.LifecycleBase:
在生命周期的相应方法中获取state属性,直接返回的state
public LifecycleState getState() { return this.state; } public String getStateName() { return this.getState().toString(); }
