一、mina总体框架与案例：
1.总体结构图：
简述：以上是一张来自网上比較经典的图，总体上揭示了mina的结构，当中IoService包括clientIoConnector和服务端IoAcceptor两部分。即不管是client还是服务端都是这个结构。IoService封装了网络传输层（TCP和UDP），而IoFilterChain中mina自带的filter做了一些主要的操作之外，支持扩展。经过FilterChain之后终于调用IoHandler，IoHandler是详细实现业务逻辑的处理接口，详细的业务实现可扩展。
2.一个可执行的案例（案例来自网上，转载后试验）：
Client.java:
import java.net.InetSocketAddress;
import java.nio.charset.Charset;
import java.util.Random;
import org.apache.mina.core.future.ConnectFuture;
import org.apache.mina.core.future.IoFutureListener;
import org.apache.mina.core.service.IoConnector;
import org.apache.mina.core.service.IoHandlerAdapter;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.transport.socket.nio.NioSocketConnector;
public class Client extends IoHandlerAdapter {
private Random random = new Random(System.currentTimeMillis());
public Client() {
IoConnector connector = new NioSocketConnector();
connector.getFilterChain().addLast(
"text",
new ProtocolCodecFilter(new TextLineCodecFactory(Charset
.forName(Server.ENCODE))));
connector.setHandler(this);
ConnectFuture future = connector.connect(new InetSocketAddress(
"127.0.0.1", Server.PORT));
future.awaitUninterruptibly();
future.addListener(new IoFutureListener<ConnectFuture>() {
@Override
public void operationComplete(ConnectFuture future) {
IoSession session = future.getSession();
while (!session.isClosing()) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
String message = "你好。我roll了" + random.nextInt(100) + "点.";
session.write(message);
}
}
});
connector.dispose();
}
@Override
public void messageReceived(IoSession session, Object message)
throws Exception {
System.out.println("批复:" + message.toString());
}
@Override
public void messageSent(IoSession session, Object message) throws Exception {
System.out.println("报告:" + message.toString());
}
@Override
public void exceptionCaught(IoSession session, Throwable cause)
throws Exception {
cause.printStackTrace();
session.close(true);
}
public static void main(String[] args) {
for (int i = 0; i < 10; i++) {
new Client();
}
}
}
ServerHandler.java:
import java.net.InetSocketAddress;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.mina.core.service.IoHandlerAdapter;
import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.core.session.IoSession;
public class ServerHandler extends IoHandlerAdapter {
@Override
public void exceptionCaught(IoSession session, Throwable cause)
throws Exception {
cause.printStackTrace();
session.close(false);
}
public void messageReceived(IoSession session, Object message)
throws Exception {
String s = message.toString();
System.out.println("收到请求：" + s);
if (s != null) {
int i = getPoint(s);
if (session.isConnected()) {
if (i >= 95) {
session.write("运气不错，你能够出去了.");
session.close(false);
return;
}
Integer count = (Integer) session.getAttribute(Server.KEY);
count++;
session.setAttribute(Server.KEY, count);
session.write("抱歉。你运气太差了，第" + count + "次请求未被通过。继续在小黑屋呆着吧.");
} else {
session.close(true);
}
}
}
@Override
public void messageSent(IoSession session, Object message) throws Exception {
System.out.println("发给client：" + message.toString());
}
@Override
public void sessionClosed(IoSession session) throws Exception {
long l = session.getCreationTime();
System.out.println("来自" + getInfo(session) + "的会话已经关闭，它已经存活了"
+ (System.currentTimeMillis() - 1) + "毫秒");
}
@Override
public void sessionCreated(IoSession session) throws Exception {
System.out.println("给" + getInfo(session) + "创建了一个会话");
}
@Override
public void sessionIdle(IoSession session, IdleStatus status)
throws Exception {
System.out.println("来自" + getInfo(session) + "的会话闲置，状态为"
+ status.toString());
}
public void sessionOpened(IoSession session) throws Exception {
session.setAttribute(Server.KEY, 0);
System.out.println("和" + getInfo(session) + "的会话已经打开.");
}
public String getInfo(IoSession session) {
if (session == null) {
return null;
}
InetSocketAddress address = (InetSocketAddress) session
.getRemoteAddress();
int port = address.getPort();
String ip = address.getAddress().getHostAddress();
return ip + ":" + port;
}
public int getPoint(String s) {
if (s == null) {
return -1;
}
Pattern p = Pattern.compile("^[u0041-uFFFF,]*(\d+).*$");
Matcher m = p.matcher(s);
if (m.matches()) {
return Integer.valueOf(m.group(1));
}
return 0;
}
}
Server.java:
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.charset.Charset;
import org.apache.mina.filter.codec.ProtocolCodecFilter;
import org.apache.mina.filter.codec.textline.TextLineCodecFactory;
import org.apache.mina.transport.socket.SocketAcceptor;
import org.apache.mina.transport.socket.nio.NioSocketAcceptor;
public class Server {
public static final int PORT = 2534;
public static String ENCODE = "UTF-8";
public static final String KEY = "roll";
public static void main(String[] args){
SocketAcceptor acceptor = new NioSocketAcceptor();
acceptor.getFilterChain().addLast(
"text",
new ProtocolCodecFilter(new TextLineCodecFactory(Charset
.forName(ENCODE))));
acceptor.setHandler(new ServerHandler());
try {
acceptor.bind(new InetSocketAddress(PORT));
System.out.println("游戏開始，你想出去吗，来，碰碰运气吧！");
} catch (IOException e) {
e.printStackTrace();
acceptor.dispose();
}
}
}
本案例依赖的jar例如以下图：
简述：以上是依赖mina实现的一个可执行的案例，就不多说了，结合总体的结构图和案例实现能够看出mina框架还是非常轻量级的。以下分析一下mina的源代码结构和一些时序流程。
二、mina 核心源代码分析：
1.mina的启动时序(结合上面的案例)：
简述：SocketAcceptor作为服务端对外启动接口类，在bind网络地址的时候，会触发服务端一系列服务的启动，从调用链能够清晰找到相应的源代码阅读。
当中AbstractPollingIoAcceptor是一个核心类，它会调用自身的startupAcceptor方法，来启动一个存放Acceptor的线程池用来处理client传输过来的请求。
AbstractPollingIoAcceptor 类的 startupAcceptor 方法例如以下：
/**
* This method is called by the doBind() and doUnbind()
* methods. If the acceptor is null, the acceptor object will
* be created and kicked off by the executor. If the acceptor
* object is null, probably already created and this class
* is now working, then nothing will happen and the method
* will just return.
*/
private void startupAcceptor() throws InterruptedException {
// If the acceptor is not ready, clear the queues
// TODO : they should already be clean : do we have to do that ?
if (!selectable) {
registerQueue.clear();
cancelQueue.clear();
}
// start the acceptor if not already started
Acceptor acceptor = acceptorRef.get();
//这里仅仅会启动一个worker
if (acceptor == null) {
lock.acquire();
acceptor = new Acceptor();
if (acceptorRef.compareAndSet(null, acceptor)) {
executeWorker(acceptor);
} else {
lock.release();
}
}
}
上面调用到 AbstractIoService 的 executeWorker方法例如以下：
protected final void executeWorker(Runnable worker) {
executeWorker(worker, null);
}
protected final void executeWorker(Runnable worker, String suffix) {
String actualThreadName = threadName;
if (suffix != null) {
actualThreadName = actualThreadName + '-' + suffix;
}
executor.execute(new NamePreservingRunnable(worker, actualThreadName));
}
简述：有类AbstractPollingIoAcceptor 的 startupAcceptor方法（上文）能够看到，一个SocketAcceptor仅仅启动了一个Worker线程（即代码中的Acceptor对象）而且把他加到线程池中。反过来讲，也能够看出AbstractIoService维护了Worker的线程池。（ps：这个Worker就是服务端处理请求的线程）。
2.Mina处理client链接的过程（启动后）：
概述：从1中的启动时序能够看到，启动过程通过创建SocketAcceptor将有类AbstractPollingIoAcceptor的内部类Acceptor放到了 AbstractIoService的线程池里面，而这个Acceptor就是处理client网络请求的worker。而以下这个时序就是线程池中每一个worker处理client网络请求的时序流程。
处理请求时序： 
简述：worker线程Acceptor的run方法中会调用NioSocketAcceptor或者AprSocketAccetpor的select方法。
ps:APR（Apache Protable Runtime Library，Apache可移植执行库）是能够提供非常好的可拓展性、性能以及对底层操作系统一致性操作的技术，说白了就是apache实现的一套标准的通讯接口。
AprSocketAcceptor先不做深入了解，主要了解下NioSocketAcceptor，NioSocketAcceptor顾名思义，它调用了java NIO的API实现了NIO的网络连接处理过程。
AbstractPolling$Acceptor 的run方法的核心代码例如以下：
private class Acceptor implements Runnable {
public void run() {
assert (acceptorRef.get() == this);
int nHandles = 0;
// Release the lock
lock.release();
while (selectable) {
try {
// Detect if we have some keys ready to be processed
// The select() will be woke up if some new connection
// have occurred, or if the selector has been explicitly
// woke up
//调用了NioSocketAcceptor的select方法，获取了selectKey
int selected = select();
// this actually sets the selector to OP_ACCEPT,
// and binds to the port on which this class will
// listen on
nHandles += registerHandles();
// Now, if the number of registred handles is 0, we can
// quit the loop: we don't have any socket listening
// for incoming connection.
if (nHandles == 0) {
acceptorRef.set(null);
if (registerQueue.isEmpty() && cancelQueue.isEmpty()) {
assert (acceptorRef.get() != this);
break;
}
if (!acceptorRef.compareAndSet(null, this)) {
assert (acceptorRef.get() != this);
break;
}
assert (acceptorRef.get() == this);
}
if (selected > 0) {
// We have some connection request, let's process
// them here.
processHandles(selectedHandles());
}
// check to see if any cancellation request has been made.
nHandles -= unregisterHandles();
} catch (ClosedSelectorException cse) {
// If the selector has been closed, we can exit the loop
break;
} catch (Throwable e) {
ExceptionMonitor.getInstance().exceptionCaught(e);
try {
Thread.sleep(1000);
} catch (InterruptedException e1) {
ExceptionMonitor.getInstance().exceptionCaught(e1);
}
}
}
// Cleanup all the processors, and shutdown the acceptor.
if (selectable && isDisposing()) {
selectable = false;
try {
if (createdProcessor) {
processor.dispose();
}
} finally {
try {
synchronized (disposalLock) {
if (isDisposing()) {
destroy();
}
}
} catch (Exception e) {
ExceptionMonitor.getInstance().exceptionCaught(e);
} finally {
disposalFuture.setDone();
}
}
}
}
简述：从上面的代码中能够看出一个典型的网络请求处理的程序，在循环中拿到处理的请求后就调用AbstractPollingIoAcceptor的processHandles（）对网络请求做处理。
代码例如以下：
/**
* This method will process new sessions for the Worker class. All
* keys that have had their status updates as per the Selector.selectedKeys()
* method will be processed here. Only keys that are ready to accept
* connections are handled here.
* <p/>
* Session objects are created by making new instances of SocketSessionImpl
* and passing the session object to the SocketIoProcessor class.
*/
@SuppressWarnings("unchecked")
private void processHandles(Iterator<H> handles) throws Exception {
while (handles.hasNext()) {
H handle = handles.next();
handles.remove();
// Associates a new created connection to a processor,
// and get back a session
//这里调用了NioSocketAcceptor的accept方法
S session = accept(processor, handle);
if (session == null) {
continue;
}
initSession(session, null, null);
// add the session to the SocketIoProcessor
// 这步处理add操作，会触发对client请求的异步处理。
session.getProcessor().add(session);
}
}
NioSocketAcceptor的accept方法new了一个包装Process处理线程的session实例:而且在调用session.getProcessor().add(session)的操作的时候触发了对client请求的异步处理。
/**
* {@inheritDoc}
*/
@Override
protected NioSession accept(IoProcessor<NioSession> processor, ServerSocketChannel handle) throws Exception {
SelectionKey key = handle.keyFor(selector);
if ((key == null) || (!key.isValid()) || (!key.isAcceptable())) {
return null;
}
// accept the connection from the client
SocketChannel ch = handle.accept();
if (ch == null) {
return null;
}
return new NioSocketSession(this, processor, ch);
}
再看上面时序图：有一步是AbstractPollingIoProcessor调用了startupProcessor方法。代码例如以下：
/**
* Starts the inner Processor, asking the executor to pick a thread in its
* pool. The Runnable will be renamed
*/
private void startupProcessor() {
Processor processor = processorRef.get();
if (processor == null) {
processor = new Processor();
if (processorRef.compareAndSet(null, processor)) {
executor.execute(new NamePreservingRunnable(processor, threadName));
}
}
// Just stop the select() and start it again, so that the processor
// can be activated immediately.
wakeup();
}
简述：这个startupProcessor方法在调用 session里包装的processor的add方法是，触发了将处理client请求的processor放入异步处理的线程池中。兴许详细Processor怎么处理client请求的流程，涉及到FilterChain的过滤。以及Adapter的调用。用来处理业务逻辑。详细的异步处理时序看以下的时序图：
简述：这个时序就是将待处理的client链接，通过NIO的形式接受请求，并将请求包装成Processor的形式放到处理的线程池中异步的处理。
在异步的处理过程中则调用了Processor的run方法，详细的filterchain的调用和业务Adapter的调用也是在这一步得到处理。
值得注意的是。Handler的调用是封装在DefaultFilterchain的内部类诶TairFilter中触发调用的。Processor的run方法代码例如以下：
private class Processor implements Runnable {
public void run() {
assert (processorRef.get() == this);
int nSessions = 0;
lastIdleCheckTime = System.currentTimeMillis();
for (;;) {
try {
// This select has a timeout so that we can manage
// idle session when we get out of the select every
// second. (note : this is a hack to avoid creating
// a dedicated thread).
long t0 = System.currentTimeMillis();
//调用了NioProcessor
int selected = select(SELECT_TIMEOUT);
long t1 = System.currentTimeMillis();
long delta = (t1 - t0);
if ((selected == 0) && !wakeupCalled.get() && (delta < 100)) {
// Last chance : the select() may have been
// interrupted because we have had an closed channel.
if (isBrokenConnection()) {
LOG.warn("Broken connection");
// we can reselect immediately
// set back the flag to false
wakeupCalled.getAndSet(false);
continue;
} else {
LOG.warn("Create a new selector. Selected is 0, delta = " + (t1 - t0));
// Ok, we are hit by the nasty(讨厌的) epoll
// spinning.
// Basically, there is a race condition
// which causes a closing file descriptor not to be
// considered as available as a selected channel, but
// it stopped the select. The next time we will
// call select(), it will exit immediately for the same
// reason, and do so forever, consuming 100%
// CPU.
// We have to destroy the selector, and
// register all the socket on a new one.
registerNewSelector();
}
// Set back the flag to false
wakeupCalled.getAndSet(false);
// and continue the loop
continue;
}
// Manage newly created session first
nSessions += handleNewSessions();
updateTrafficMask();
// Now, if we have had some incoming or outgoing events,
// deal with them
if (selected > 0) {
//LOG.debug("Processing ..."); // This log hurts one of the MDCFilter test...
//触发了详细的调用逻辑
process();
}
// Write the pending requests
long currentTime = System.currentTimeMillis();
flush(currentTime);
// And manage removed sessions
nSessions -= removeSessions();
// Last, not least, send Idle events to the idle sessions
notifyIdleSessions(currentTime);
// Get a chance to exit the infinite loop if there are no
// more sessions on this Processor
if (nSessions == 0) {
processorRef.set(null);
if (newSessions.isEmpty() && isSelectorEmpty()) {
// newSessions.add() precedes startupProcessor
assert (processorRef.get() != this);
break;
}
assert (processorRef.get() != this);
if (!processorRef.compareAndSet(null, this)) {
// startupProcessor won race, so must exit processor
assert (processorRef.get() != this);
break;
}
assert (processorRef.get() == this);
}
// Disconnect all sessions immediately if disposal has been
// requested so that we exit this loop eventually.
if (isDisposing()) {
for (Iterator<S> i = allSessions(); i.hasNext();) {
scheduleRemove(i.next());
}
wakeup();
}
} catch (ClosedSelectorException cse) {
// If the selector has been closed, we can exit the loop
break;
} catch (Throwable t) {
ExceptionMonitor.getInstance().exceptionCaught(t);
try {
Thread.sleep(1000);
} catch (InterruptedException e1) {
ExceptionMonitor.getInstance().exceptionCaught(e1);
}
}
}
try {
synchronized (disposalLock) {
if (disposing) {
doDispose();
}
}
} catch (Throwable t) {
ExceptionMonitor.getInstance().exceptionCaught(t);
} finally {
disposalFuture.setValue(true);
}
}
}
简述：这么一坨代码能够看出，这个处理器也调用了java的Nio API是一个NIO模型。当中select和process方法各自是从session拿到要处理的请求，并进行处理。而详细的Processor实例是NioProcessor。从加入凝视的代码中有一步调用了自身的process方法，这步调用触发了详细业务逻辑的调用。能够结合代码和时序图看下。在Process方法中会调用reader（session）或wirte（session）方法，然后调用fireMessageReceived方法，这种方法又调用了callNextMessageReceived方法致使触发了整个FilterChain和Adapter的调用。read方法的核心代码例如以下：
private void read(S session) {
IoSessionConfig config = session.getConfig();
int bufferSize = config.getReadBufferSize();
IoBuffer buf = IoBuffer.allocate(bufferSize);
final boolean hasFragmentation = session.getTransportMetadata().hasFragmentation();
try {
int readBytes = 0;
int ret;
try {
if (hasFragmentation) {
while ((ret = read(session, buf)) > 0) {
readBytes += ret;
if (!buf.hasRemaining()) {
break;
}
}
} else {
ret = read(session, buf);
if (ret > 0) {
readBytes = ret;
}
}
} finally {
buf.flip();
}
if (readBytes > 0) {
IoFilterChain filterChain = session.getFilterChain();
filterChain.fireMessageReceived(buf);
buf = null;
if (hasFragmentation) {
if (readBytes << 1 < config.getReadBufferSize()) {
session.decreaseReadBufferSize();
} else if (readBytes == config.getReadBufferSize()) {
session.increaseReadBufferSize();
}
}
}
if (ret < 0) {
scheduleRemove(session);
}
} catch (Throwable e) {
if (e instanceof IOException) {
if (!(e instanceof PortUnreachableException)
|| !AbstractDatagramSessionConfig.class.isAssignableFrom(config.getClass())
|| ((AbstractDatagramSessionConfig) config).isCloseOnPortUnreachable()) {
scheduleRemove(session);
}
}
IoFilterChain filterChain = session.getFilterChain();
filterChain.fireExceptionCaught(e);
}
}
从这段代码并结合上面的时序图能够看出来触发整个FilterChain的调用以及IoHandler的调用。
三、类结构分析
參考第一部分的总体结构图，画一下每一个部分大致的类结构图：
简述： 从类继承结构图来看，能够看到在IOService体系下，存在IoConnector和IoAcceptor两个大的分支体系。IoConnector是做为client的时候使用，IoAcceptor是作为服务端的时候使用。实际上在Mina中，有三种worker线程各自是：Acceptor、Connector 和 I/O processor。
(1) Acceptor Thread 作为server端的链接线程，实现了IoService接口。线程的数量就是创建SocketAcceptor的数量。
(2) Connector Thread 作为client请求建立的链接线程，实现了IoService接口，维持了一个和服务端Acceptor的一个链接，线程的数量就是创建SocketConnector的数量。
(3) I/O processorThread 作为I/O真正处理的线程，存在于server端和client。线程的数量是能够配置的，默认是CPU个数+1。
上面那个图仅仅是表述了IoService类体系，而I/O Processor的类体系并不在当中，见下图：
简述：IOProcessor主要分为两种。各自是AprIOProcessor和NioProcessor，Apr的解释见上文：ps:APR（Apache Protable Runtime Library，Apache可移植执行库）。
NioProcessor也是Nio的一种实现，用来处理client连接过来的请求。在Processor中会调用到 FilterChain 和 Handler，见上文代码。先看下FilterChain的类结构图例如以下：
Filter 和 Handler的类结构例如以下：
Handler的类结构例如以下：
Mina的session类结构图例如以下：
Mina的Buffer的类结构图例如以下：
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