网络编程基础(4) : IO多路复用(多线程)

1. 简述

本篇文章延续上一篇网络编程基础(3)
: IO多路复用(单线程)之内容，做出了进一步的改善。

IO复用网路模型中的角色Handler，将以状态模式(State Pattern)实现，

并且将Handler接收完网络消息后的业务逻辑处理交由工作线程实现，所有的工作线程以线程池来维护。

2. 网络模型

3. 代码实现

[TCPReactor.java]

// Reactor線程
package server;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.util.Iterator;
import java.util.Set;

public class TCPReactor implements Runnable {

private final ServerSocketChannel ssc;
private final Selector selector;

public TCPReactor(int port) throws IOException {
selector = Selector.open();
ssc = ServerSocketChannel.open();
InetSocketAddress addr = new InetSocketAddress(port);
ssc.socket().bind(addr); // 在ServerSocketChannel綁定監聽端口
ssc.configureBlocking(false); // 設置ServerSocketChannel為非阻塞
SelectionKey sk = ssc.register(selector, SelectionKey.OP_ACCEPT); // ServerSocketChannel向selector註冊一個OP_ACCEPT事件，然後返回該通道的key
sk.attach(new Acceptor(selector, ssc)); // 給定key一個附加的Acceptor對象
}

@Override
public void run() {
while (!Thread.interrupted()) { // 在線程被中斷前持續運行
System.out.println("Waiting for new event on port: " + ssc.socket().getLocalPort() + "...");
try {
if (selector.select() == 0) // 若沒有事件就緒則不往下執行
continue;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Set<SelectionKey> selectedKeys = selector.selectedKeys(); // 取得所有已就緒事件的key集合
Iterator<SelectionKey> it = selectedKeys.iterator();
while (it.hasNext()) {
dispatch((SelectionKey) (it.next())); // 根據事件的key進行調度
it.remove();
}
}
}

/*
* name: dispatch(SelectionKey key)
* description: 調度方法，根據事件綁定的對象開新線程
*/
private void dispatch(SelectionKey key) {
Runnable r = (Runnable) (key.attachment()); // 根據事件之key綁定的對象開新線程
if (r != null)
r.run();
}

}

[Acceptor.java]

// 接受連線請求線程
package server;

import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

public class Acceptor implements Runnable {

private final ServerSocketChannel ssc;
private final Selector selector;

public Acceptor(Selector selector, ServerSocketChannel ssc) {
this.ssc=ssc;
this.selector=selector;
}

@Override
public void run() {
try {
SocketChannel sc= ssc.accept(); // 接受client連線請求
System.out.println(sc.socket().getRemoteSocketAddress().toString() + " is connected.");

if(sc!=null) {
sc.configureBlocking(false); // 設置為非阻塞
SelectionKey sk = sc.register(selector, SelectionKey.OP_READ); // SocketChannel向selector註冊一個OP_READ事件，然後返回該通道的key
selector.wakeup(); // 使一個阻塞住的selector操作立即返回
sk.attach(new TCPHandler(sk, sc)); // 給定key一個附加的TCPHandler對象
}

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

[TCPHandler.java]

// Handler線程
package server;

import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class TCPHandler implements Runnable {

private final SelectionKey sk;
private final SocketChannel sc;
private static final int THREAD_COUNTING = 10;
private static ThreadPoolExecutor pool = new ThreadPoolExecutor(
THREAD_COUNTING, THREAD_COUNTING, 10, TimeUnit.SECONDS,
new LinkedBlockingQueue<Runnable>()); // 線程池

HandlerState state; // 以狀態模式實現Handler

public TCPHandler(SelectionKey sk, SocketChannel sc) {
this.sk = sk;
this.sc = sc;
state = new ReadState(); // 初始狀態設定為READING
pool.setMaximumPoolSize(32); // 設置線程池最大線程數
}

@Override
public void run() {
try {
state.handle(this, sk, sc, pool);

} catch (IOException e) {
System.out.println("[Warning!] A client has been closed.");
closeChannel();
}
}

public void closeChannel() {
try {
sk.cancel();
sc.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}

public void setState(HandlerState state) {
this.state = state;
}
}

Handler要以状态模式实现还需要定义状态接口(interface)和状态实现类(ConcreteState Class)
[HandlerState.java]

package server;

import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.ThreadPoolExecutor;

public interface HandlerState {

public void changeState(TCPHandler h);

public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,
ThreadPoolExecutor pool) throws IOException ;
}

[ReadState.java]

package server;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.ThreadPoolExecutor;

public class ReadState implements HandlerState{

private SelectionKey sk;

public ReadState() {
}

@Override
public void changeState(TCPHandler h) {
// TODO Auto-generated method stub
h.setState(new WorkState());
}

@Override
public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,
ThreadPoolExecutor pool) throws IOException { // read()
this.sk = sk;
// non-blocking下不可用Readers，因為Readers不支援non-blocking
byte[] arr = new byte[1024];
ByteBuffer buf = ByteBuffer.wrap(arr);

int numBytes = sc.read(buf); // 讀取字符串
if(numBytes == -1)
{
System.out.println("[Warning!] A client has been closed.");
h.closeChannel();
return;
}
String str = new String(arr); // 將讀取到的byte內容轉為字符串型態
if ((str != null) && !str.equals(" ")) {
h.setState(new WorkState()); // 改變狀態(READING->WORKING)
pool.execute(new WorkerThread(h, str)); // do process in worker thread
System.out.println(sc.socket().getRemoteSocketAddress().toString()
+ " > " + str);
}

}

/*
* 執行邏輯處理之函數
*/
synchronized void process(TCPHandler h, String str) {
// do process(decode, logically process, encode)..
// ..
h.setState(new WriteState()); // 改變狀態(WORKING->SENDING)
this.sk.interestOps(SelectionKey.OP_WRITE); // 通過key改變通道註冊的事件
this.sk.selector().wakeup(); // 使一個阻塞住的selector操作立即返回
}

/*
* 工作者線程
*/
class WorkerThread implements Runnable {

TCPHandler h;
String str;

public WorkerThread(TCPHandler h, String str) {
this.h = h;
this.str=str;
}

@Override
public void run() {
process(h, str);
}

}
}

[WorkState.java]

package server;

import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.ThreadPoolExecutor;

public class WorkState implements HandlerState {

public WorkState() {
}

@Override
public void changeState(TCPHandler h) {
// TODO Auto-generated method stub
h.setState(new WriteState());
}

@Override
public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,
ThreadPoolExecutor pool) throws IOException {
// TODO Auto-generated method stub

}

}

[WriteState.java]

package server;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.ThreadPoolExecutor;

public class WriteState implements HandlerState{

public WriteState() {
}

@Override
public void changeState(TCPHandler h) {
// TODO Auto-generated method stub
h.setState(new ReadState());
}

@Override
public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,
ThreadPoolExecutor pool) throws IOException { // send()
// get message from message queue

String str = "Your message has sent to "
+ sc.socket().getLocalSocketAddress().toString() + "\r\n";
ByteBuffer buf = ByteBuffer.wrap(str.getBytes()); // wrap自動把buf的position設為0，所以不需要再flip()

while (buf.hasRemaining()) {
sc.write(buf); // 回傳給client回應字符串，發送buf的position位置 到limit位置為止之間的內容
}

h.setState(new ReadState()); // 改變狀態(SENDING->READING)
sk.interestOps(SelectionKey.OP_READ); // 通過key改變通道註冊的事件
sk.selector().wakeup(); // 使一個阻塞住的selector操作立即返回
}
}

最後是主程序

[Main.java]

package server;

import java.io.IOException;

public class Main {

public static void main(String[] args) {
// TODO Auto-generated method stub
try {
TCPReactor reactor = new TCPReactor(1333);
reactor.run();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

对应的客户端可以参考网络编程基础(3) : IO多路复用(单线程)中的代码

下一篇将介绍採用了多个Reactor的IO复用模型实现