一直以来的多线程的基础总结都是脱离应用的，但是要说多线程的应用就不能不说Mina。Apache Mina作为一个高性能的Java异步并发网 络通讯框架，其内部的多线程的设计和实现可谓是学习多线程的良药。手上的Mina源码是svn剪下来的最新的代码，mvn转化成eclipse项目 后导入mina-core的源码看看多线程的应用吧。
首先简单的介绍在org.apache.mina.core.service包里的核心接口之一：IoService。这个接口是对于服务器端接收连接和客户端发起连 接这两种服务的顶层抽象，所以就有了IoAcceptor和IoConnector两个子接口的继承与隔离。很拍马屁的说，从这个小细节可以看到mina架 构的精细。这种程度的接口的隔离最重要的就是对接口内抽象行为的准确划分，错误的划分接口的职责将使得后面得实现显得不合理甚至是 错误。只是不知道负责抽象的设计人员是否是一次性的抽象成功，如果是只能说牛x。至于交互会话IoSession和实际的I/O操作处理器 IoProcessor 以及底层处理I/O事件的IoHandle这些接口就不废话了，今天看的是与IoServiceListener有关的多线程应用。 IoServiceListener主要是用来监听IoService相关的事件，而今日主角--IoServiceListenerSupport则是用来把IoService和对应的 IoServiceListener包装在一起进行管理的辅助类。先看看其源码：
Java代码
public class IoServiceListenerSupport {
/** The {@link IoService} that this instance manages. */
private final IoService service;
/** A list of {@link IoServiceListener}s. */
private final List<IoServiceListener> listeners = new CopyOnWriteArrayList<IoServiceListener> ();
/** Tracks managed sessions. */
private final ConcurrentMap<Long, IoSession> managedSessions = new ConcurrentHashMap<Long, IoSession>();
/** Read only version of {@link #managedSessions}. */
private final Map<Long, IoSession> readOnlyManagedSessions = Collections.unmodifiableMap (managedSessions);
private final AtomicBoolean activated = new AtomicBoolean();
/** Time this listenerSupport has been activated */
private volatile long activationTime;
/** A counter used to store the maximum sessions we managed since the listenerSupport has been activated */
private volatile int largestManagedSessionCount = 0;
/** A global counter to count the number of sessions managed since the start */
private volatile long cumulativeManagedSessionCount = 0;
/**
* Adds a new listener.
*
* @param listener The added listener
*/
public void add(IoServiceListener listener) {
if (listener != null) {
listeners.add(listener);
}
}
/**
* @return true if the instance is active
*/
public boolean isActive() {
return activated.get();
}
/**
* Calls {@link IoServiceListener#serviceActivated(IoService)}
* for all registered listeners.
*/
public void fireServiceActivated() {
if (!activated.compareAndSet(false, true)) {
// The instance is already active
return;
}
activationTime = System.currentTimeMillis();
// Activate all the listeners now
for (IoServiceListener listener : listeners) {
try {
listener.serviceActivated(service);
} catch (Throwable e) {
ExceptionMonitor.getInstance().exceptionCaught(e);
}
}
}
/**
* Calls {@link IoServiceListener#sessionCreated(IoSession)} for all registered listeners.
*
* @param session The session which has been created
*/
public void fireSessionCreated(IoSession session) {
boolean firstSession = false;
if (session.getService() instanceof IoConnector) {
synchronized (managedSessions) {
firstSession = managedSessions.isEmpty();
}
}
...
cumulativeManagedSessionCount ++;
...
}
}