前面两篇文章提到
NIO的server模式只有5个阶段，但是，NIO的selectionkey里确实有个accept事件，所以，为了区别，衍生出了主reactor和从reactor
并且，从reactor可以根据服务器的负荷，新增多个从reactor进行请求处理
服务器架构如下图
这个就是完整版的reactor模式的架构图了，目前使用到了reactor模式的框架（如netty），基本用的模式就是这个
代码实现：
// 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; // mainReactor用的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(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("mainReactor 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) {
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();
}
}
// 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; // mainReactor監聽的socket通道
private final int cores = Runtime.getRuntime().availableProcessors(); // 取得CPU核心數
private final Selector[] selectors = new Selector[cores]; // 創建核心數個selector給subReactor用
private int selIdx = 0; // 當前可使用的subReactor索引
private TCPSubReactor[] r = new TCPSubReactor[cores]; // subReactor線程
private Thread[] t = new Thread[cores]; // subReactor線程
public Acceptor(ServerSocketChannel ssc) throws IOException {
this.ssc = ssc;
// 創建多個selector以及多個subReactor線程
for (int i = 0; i < cores; i++) {
selectors[i] = Selector.open();
r[i] = new TCPSubReactor(selectors[i], ssc, i);
t[i] = new Thread(r[i]);
t[i].start();
}
}
@Override
public synchronized 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
r[selIdx].setRestart(true); // 暫停線程
selectors[selIdx].wakeup(); // 使一個阻塞住的selector操作立即返回
SelectionKey sk = sc.register(selectors[selIdx],
SelectionKey.OP_READ); // SocketChannel向selector[selIdx]註冊一個OP_READ事件，然後返回該通道的key
selectors[selIdx].wakeup(); // 使一個阻塞住的selector操作立即返回
r[selIdx].setRestart(false); // 重啟線程
sk.attach(new TCPHandler(sk, sc)); // 給定key一個附加的TCPHandler對象
if (++selIdx == selectors.length)
selIdx = 0;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
package server;
import java.io.IOException;
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 TCPSubReactor implements Runnable {
private final ServerSocketChannel ssc;
private final Selector selector;
private boolean restart = false;
int num;
public TCPSubReactor(Selector selector, ServerSocketChannel ssc, int num) {
this.ssc = ssc;
this.selector = selector;
this.num = num;
}
@Override
public void run() {
while (!Thread.interrupted()) { // 在線程被中斷前持續運行
//System.out.println("ID:" + num
// + " subReactor waiting for new event on port: "
// + ssc.socket().getLocalPort() + "...");
System.out.println("waiting for restart");
while (!Thread.interrupted() && !restart) { // 在線程被中斷前以及被指定重啟前持續運行
try {
if (selector.select() == 0)
continue; // 若沒有事件就緒則不往下執行
} catch (IOException e) {
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();
}
public void setRestart(boolean restart) {
this.restart = restart;
}
}
// 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;
}
}
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 ;
}
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);
}
}
}
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
}
}
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
}
}
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);
new Thread(reactor).start();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
总的来说，主从式reactor比多线程的reactor先进的地方在于：
1.主reactor是一个线程，负责监听外部的连线请求，并派发给Acceptor处理。故Main Reactor中的selector只有注册OP_ACCEPT事件，也只能监听OP_ACCEPT事件。
而处理请求是其他N个不同的线程，即从reactor
2.可以根据请求的密集度来调控从reactor的个数
参考文章：
https://blog.csdn.net/yehjordan/article/details/51026045