在學(xué)習(xí)Netty的時(shí)候，要對NIO很熟才行，這里給出一個(gè)NIO的案例代碼，方便參考。
案例
NIOServer端：
image.png
public class MultiplexerTimeServer implements Runnable {
private Selector selector;
private ServerSocketChannel servChannel;
private volatile boolean stop;
/**
* 初始化多路復(fù)用器、綁定監(jiān)聽端口
*
* @param port
*/
public MultiplexerTimeServer(int port) {
try {
// 創(chuàng)建多路復(fù)用器Selector、ServerSocketChannel
selector = Selector.open();
servChannel = ServerSocketChannel.open();
// 配置為非阻塞模式
servChannel.configureBlocking(false);
// 綁定端口，將backlog設(shè)置為1024
servChannel.socket().bind(new InetSocketAddress(port), 1024);
// 系統(tǒng)資源初始化成功后，把serverSocketChannel注冊到Selector，監(jiān)聽SelectionKey.OP_ACCEPT操作位
servChannel.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("The time server is start in port : " + port);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
public void stop() {
this.stop = true;
}
/*
* (non-Javadoc)
*
* @see java.lang.Runnable#run()
*/
@Override
public void run() {
while (!stop) {
try {
//循環(huán)體重遍歷selector，超時(shí)時(shí)間為1s。
selector.select(1000);
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectedKeys.iterator();
SelectionKey key = null;
while (it.hasNext()) {
key = it.next();
it.remove();
try {
handleInput(key);
} catch (Exception e) {
if (key != null) {
key.cancel();
if (key.channel() != null)
key.channel().close();
}
}
}
} catch (Throwable t) {
t.printStackTrace();
}
}
// 多路復(fù)用器關(guān)閉后，所有注冊在上面的Channel和Pipe等資源都會(huì)被自動(dòng)去注冊并關(guān)閉，所以不需要重復(fù)釋放資源
if (selector != null)
try {
selector.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void handleInput(SelectionKey key) throws IOException {
if (key.isValid()) {
// 處理新接入的請求消息
// 根據(jù)操作位判斷網(wǎng)絡(luò)類型。
if (key.isAcceptable()) {
// Accept the new connection
ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
SocketChannel sc = ssc.accept();
sc.configureBlocking(false);
// Add the new connection to the selector
sc.register(selector, SelectionKey.OP_READ);
}
if (key.isReadable()) {
// 讀取客戶端的消息
SocketChannel sc = (SocketChannel) key.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int readBytes = sc.read(readBuffer);
if (readBytes > 0) {
readBuffer.flip();
byte[] bytes = new byte[readBuffer.remaining()];
readBuffer.get(bytes);
String body = new String(bytes, "UTF-8");
System.out.println("The time server receive order : "
+ body);
String currentTime = "QUERY TIME ORDER"
.equalsIgnoreCase(body) ? new java.util.Date(
System.currentTimeMillis()).toString()
: "BAD ORDER";
doWrite(sc, currentTime);
} else if (readBytes < 0) {
// 對端鏈路關(guān)閉
key.cancel();
sc.close();
} else
; // 讀到0字節(jié)，忽略
}
}
}
// 發(fā)送消息異步發(fā)給客戶端。
private void doWrite(SocketChannel channel, String response)
throws IOException {
if (response != null && response.trim().length() > 0) {
byte[] bytes = response.getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
channel.write(writeBuffer);
}
}
}
NIOClient端：
image.png
public class TimeClientHandle implements Runnable {
private String host;
private int port;
private Selector selector;
private SocketChannel socketChannel;
private volatile boolean stop;
public TimeClientHandle(String host, int port) {
this.host = host == null ? "127.0.0.1" : host;
this.port = port;
try {
// 打開SocketChannel
selector = Selector.open();
socketChannel = SocketChannel.open();
// 配置偽非阻塞模式
socketChannel.configureBlocking(false);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
/*
* (non-Javadoc)
*
* @see java.lang.Runnable#run()
*/
@Override
public void run() {
try {
doConnect();
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
while (!stop) {
try {
// 輪詢Key
selector.select(1000);
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectedKeys.iterator();
SelectionKey key = null;
while (it.hasNext()) {
key = it.next();
it.remove();
try {
handleInput(key);
} catch (Exception e) {
if (key != null) {
key.cancel();
if (key.channel() != null)
key.channel().close();
}
}
}
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
// 多路復(fù)用器關(guān)閉后，所有注冊在上面的Channel和Pipe等資源都會(huì)被自動(dòng)去注冊并關(guān)閉，所以不需要重復(fù)釋放資源
if (selector != null)
try {
selector.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void handleInput(SelectionKey key) throws IOException {
if (key.isValid()) {
// 判斷是否連接成功
SocketChannel sc = (SocketChannel) key.channel();
if (key.isConnectable()) {
if (sc.finishConnect()) {
sc.register(selector, SelectionKey.OP_READ);
doWrite(sc);
} else
System.exit(1);// 連接失敗，進(jìn)程退出
}
if (key.isReadable()) {
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int readBytes = sc.read(readBuffer);
if (readBytes > 0) {
readBuffer.flip();
byte[] bytes = new byte[readBuffer.remaining()];
readBuffer.get(bytes);
String body = new String(bytes, "UTF-8");
System.out.println("Now is : " + body);
this.stop = true;
} else if (readBytes < 0) {
// 對端鏈路關(guān)閉
key.cancel();
sc.close();
} else
; // 讀到0字節(jié)，忽略
}
}
}
private void doConnect() throws IOException {
// 如果直接連接成功，則注冊到多路復(fù)用器上，發(fā)送請求消息，讀應(yīng)答
if (socketChannel.connect(new InetSocketAddress(host, port))) {
socketChannel.register(selector, SelectionKey.OP_READ);
doWrite(socketChannel);
} else
socketChannel.register(selector, SelectionKey.OP_CONNECT);
}
private void doWrite(SocketChannel sc) throws IOException {
byte[] req = "QUERY TIME ORDER".getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
writeBuffer.put(req);
writeBuffer.flip();
sc.write(writeBuffer);
if (!writeBuffer.hasRemaining())
System.out.println("Send order 2 server succeed.");
}
}
運(yùn)行結(jié)果
image.png
image.png
最后
基本概念，就不多說了。Nio編程中客戶端和服務(wù)端都會(huì)使用Selector輪詢Channel的事件，不同的是客戶端使用的是SocketChannel，服務(wù)端使用的是ServerSocketChannel，服務(wù)端要監(jiān)聽端口，而客戶端進(jìn)行連接。
Nio編程是Netty中很重要的基礎(chǔ)，希望大家能掌握。
