Java NIO 反應器模式

Java NIO 反應器模式簡單模型

一般NIO裡反應器模式都是這樣：一個Acceptor（當然多個也行，不過一般場景一個夠了）負責accept事件，把接收到Socket CHannel註冊到按某種演算法從在 Reactor池中取出的一個Reactor上，註冊的事件為讀，寫等，之後這個Socket Channel的所有IO事件都和Acceptor沒關係，都由被註冊到的那個Reactor來負責。

每個Acceptor和每個Reactor都各自持有一個Selector

當然每個Acceptor和Reactor都得是一個線程（起碼在邏輯上得是線程）

簡單實現，三個類NioAcceptor、NioReactor和ReactorPool ：

package cc.lixiaohui.demo.dp.reator;
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.nio.channels.SocketChannel;
import java.util.Objects;
import java.util.Set;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
 * Acceptor负责处理SelectionKey.OP_ACCEPT事件, 将接收到的SocketChannel注册到Reactor上去
 */
public class NioAcceptor {
private int port;
private String host;
private Selector selector; // Java NIO Selector
private final ServerSocketChannel serverChannel; // Java NIO ServerSocketChannel
private ReactorPool reactorPool; // NioReactor池
private Thread thread; // 工作线程
private volatile boolean stop = false;
private static final Logger logger = LoggerFactory.getLogger(NioAcceptor.class);
public NioAcceptor(int port, String host, int reactorPoolSize) throws IOException {
this.port = port;
this.host = Objects.requireNonNull(host);
this.reactorPool = new ReactorPool(reactorPoolSize);
selector = Selector.open(); // 创建selector
serverChannel = ServerSocketChannel.open(); // new server socket channel
serverChannel.configureBlocking(false); // in non-blocking mode
serverChannel.bind(new InetSocketAddress(host, port)); // bind
serverChannel.register(selector, SelectionKey.OP_ACCEPT); // 
}
public void stop() throws InterruptedException {
stop = true;
thread.join();
}
public void start() {
thread = new Thread(new AcceptTask(this));
thread.start();
}
private static class AcceptTask implements Runnable {
NioAcceptor acceptor;
AcceptTask(NioAcceptor acceptor) {
this.acceptor = acceptor;
}
public void run() {
final Selector selector = acceptor.selector;
Set<SelectionKey> keys = null;
while (!acceptor.stop) { // 运行中
try {
selector.select(1000L); // select, 最多等1秒
keys = selector.selectedKeys();
try {
for (SelectionKey key : keys) {
if (key.isValid() && key.isAcceptable()) { // 可accept
SocketChannel channel = acceptor.serverChannel.accept();
channel.configureBlocking(false);
// 取下一个Reactor并把SocketChannel加入到Reactor的注册队列
acceptor.reactorPool.nextReactor().postRegistry(channel);
} else {
key.cancel();
}
}
} finally {
keys.clear();
}
} catch (IOException e) {
logger.error("", e);
}
}
}
}
}

/**
 * Reactor负责SelectionKey.OP_READ | SelectionKey.OP_WRITE等事件
 */
public class NioReactor {
/** 待注册的{@link SocketChannel} 队列 */
private Queue<SocketChannel> registerQueue = new ConcurrentLinkedQueue<SocketChannel>();
private Selector selector;
private volatile boolean stop = false;
private Thread thread;
private static final Logger logger = LoggerFactory.getLogger(NioReactor.class);
public NioReactor() throws IOException {
selector = Selector.open();
}
public void postRegistry(SocketChannel channel) {
registerQueue.add(channel);
selector.wakeup(); // 唤醒selector, 以便让其即时处理注册
}
public NioReactor start() {
thread = new Thread(new ReactTask(this));
thread.start();
return this;
}
public void stop() throws InterruptedException {
stop = true;
thread.join();
}
/**
* 处理队列里面的待注册的SocketChannel
*/
private void doRegister(Selector selector) {
while (!registerQueue.isEmpty()) {
SocketChannel channel = registerQueue.poll();
try {
// 注册读事件, 写事件无需注册, 写事件是业务驱动的, 当往channel写入 数据未写完时再注册写事件
channel.register(selector, SelectionKey.OP_READ); 
} catch (ClosedChannelException e) {
logger.error("", e);
}
}
}
private void handleWrite(SelectionKey key) {
// TODO 业务写
}
private void handleRead(SelectionKey key) {
// TODO 业务读
}
private static class ReactTask implements Runnable {
NioReactor reactor;
ReactTask(NioReactor reactor) {
this.reactor = reactor;
}
public void run() {
Set<SelectionKey> keys = null;
while (!reactor.stop) {
final Selector selector = reactor.selector;
try {
selector.select(500L);
reactor.doRegister(selector); // 处理注册
keys = selector.selectedKeys();
for (SelectionKey key : keys) {
try {
if (!key.isValid()) { // not valid
key.cancel();
continue;
}
if (key.isReadable()) { // 可读
reactor.handleRead(key);
}
if (key.isWritable()) { // 可写
reactor.handleWrite(key);
}
} catch (Throwable t) {
logger.error("", t);
continue;
}
}
} catch (IOException e) {
logger.error("", e);
}
}
}
}
 }

ReactorPool用來管理Reactor：

public class ReactorPool extends LinkedList<NioReactor>{
private static final long serialVersionUID = 6525233920805533099L;
private final int capacity;
public ReactorPool(int size) {
this.capacity = size;
}
// 轮询算法取下一个Reactor
public NioReactor nextReactor() throws IOException {
// 新建或从头部拿一个Reactor
NioReactor reactor = size() < capacity ? new NioReactor().start() : poll();
add(reactor);// 加到尾部
return reactor;
}
}