Java IO多路复用技术简介

文章由LinuxBoy分享于2019-04-01 05:04:00热评（206）

Java IO多路复用技术简介

/**
* @author qifuguang
* @date 15-2-4 下午2:07
*/
public class TimeServerMain {
public static void main(String[] args) throws Exception {
// 启动时间服务器
new Thread(new SelectorTimeServer()).start();
}
}

/**
* @author qifuguang
* @date 15-2-4 下午2:09
*/
public class TimeClientMain {
public static void main(String[] args) throws Exception {
// 创建100个客户端连接到服务器
for (int i = 0; i < 100; i++) {
new Thread(new SelectorTimeClient(i + 1)).start();
}
}
}

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;

/**
* @author qifuguang
* @date 15-2-4 下午1:21
*/
public class SelectorTimeServer implements Runnable {
private static final String TIME_ORDER = "Query Time";
private Selector selector;
private ServerSocketChannel serverChannel;
private volatile boolean stop = false;

/**
* 创建Selector, 创建ServerSocketChannel,并设置为非阻塞模式, 注册到selector.
*
* @throws Exception
*/
public SelectorTimeServer() throws Exception {
selector = Selector.open();
serverChannel = ServerSocketChannel.open();
serverChannel.socket().bind(new InetSocketAddress(8080));
serverChannel.configureBlocking(false);
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
}

/**
* 轮询监听selector.
*/
@Override
public void run() {
try {
System.out.println("时间服务器启动！");
while (!stop) {
selector.select(1000);
Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
iterator.remove();
handleKey(key);
}
}
if (selector != null) {
selector.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 处理每一种selector感兴趣的事件.
*
* @param key 轮询监听得到的SelectionKey.
*/
private void handleKey(SelectionKey key) {
try {
if (key.isValid()) { // 如果连接成功
if (key.isAcceptable()) { // 监听到有新客户端连接
SocketChannel accept = ((ServerSocketChannel) key.channel()).accept(); // 建立与客户端的连接
accept.configureBlocking(false); // 设置该连接为非阻塞模式
accept.register(selector, SelectionKey.OP_READ); // 将该连接注册到selector
System.out.println("发现有新客户端连接...");
}
if (key.isReadable()) { // 监听到有客户端发送请求
SocketChannel channel = (SocketChannel) key.channel();
// 读取客户端发来的请求
ByteBuffer buff = ByteBuffer.allocate(1024);
int size = channel.read(buff);
if (size > 0) {
byte[] b = new byte[size];
buff.flip();
buff.get(b);
String order = new String(b, "UTF-8");
System.out.println("收到客户端命令：" + order);
String content = "";
if (order.equalsIgnoreCase(TIME_ORDER)) {
content = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
} else {
content = "命令错误";
}
// 根据客户端发来的请求做出相应的动作,并将处理结果返回给客户端
doWrite(channel, content);
} else if (size < 0) {
channel.close();
key.cancel();
} else {
;
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 向指定的SocketChannel发送指定的消息。
*
* @param sc 需要向哪一个SocketChannel发送消息
* @param content 需要发送的消息
* @throws Exception
*/
private void doWrite(SocketChannel sc, String content) throws Exception {
ByteBuffer buffer = ByteBuffer.allocate(1024);
buffer.put(content.getBytes("UTF-8"));
buffer.flip();
sc.write(buffer);
if (!buffer.hasRemaining()) {
System.out.println("下发消息给客户端：" + content);
}
}
}

/**
* @author qifuguang
* @date 15-2-4 下午1:21
*/
public class SelectorTimeClient implements Runnable {
private static final String TIME_ORDER = "Query Time";
private SocketChannel channel;
private Selector selector;
private volatile boolean stop = false;
private Integer index;

/**
* 创建Selector, SocketChannel.
*
* @param index 客户端编号.
* @throws Exception
*/
public SelectorTimeClient(Integer index) throws Exception {
selector = Selector.open();
channel = SocketChannel.open();
channel.configureBlocking(false);
this.index = index;
}

/**
* 轮询监听selector刚兴趣的事件.
*/
@Override
public void run() {
try {
System.out.println("第" + index + "个客户端启动!");
// 先尝试异步连接服务器, 如果连接成功,则只需要把channel注册到selector的READ事件,
// 读取服务器返回的结果. 如果不成功（客户端已经向服务器发送了sync包,但是服务器没有返回ack包, 物理链路还没建立成功）
// 则把该channel注册到selector的CONNECT事件, 等待服务器返回的ack包.
if (channel.connect(new InetSocketAddress(8080))) {
channel.register(selector, SelectionKey.OP_READ);
doWrite(channel, TIME_ORDER);
} else {
channel.register(selector, SelectionKey.OP_CONNECT);
}
while (!stop) {
selector.select(1000);
Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
SocketChannel sc = (SocketChannel) key.channel();
iterator.remove();
if (key.isValid()) {
if (key.isReadable()) { // 监听到可读事件, 读取服务器返回的处理结果.
ByteBuffer buff = ByteBuffer.allocate(1024);
int size = sc.read(buff);
if (size > 0) {
byte[] b = new byte[size];
buff.flip();
buff.get(b);
System.out.println("第" + index + "个客户端获取服务器返回时间：" + new String(b));
stop = true;
} else if (size < 0) {
sc.close();
key.cancel();
} else {
;
}
}
if (key.isConnectable()) { //监听到服务器返回了ack包, 准备完成连接的建立
if (sc.finishConnect()) { // 调用此方法完成物理链路连接的建立
sc.register(selector, SelectionKey.OP_READ); // 建立连接之后注册监听READ事件
doWrite(sc, TIME_ORDER);
} else {
System.exit(1); //否则,程序退出
}
}
}
}
}
if (selector != null) {
selector.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 向指定的channel发送指定的消息.
*
* @param channel 向哪一个channel发送消息
* @param content 需要发送的消息
* @throws Exception
*/
private void doWrite(SocketChannel channel, String content) throws Exception {
ByteBuffer buff = ByteBuffer.allocate(1024);
buff.put(content.getBytes("UTF-8"));
buff.flip();
channel.write(buff);
if (!buff.hasRemaining()) {
System.out.println("第" + index + "个客户端成功发送请求到服务器：" + content);
}
}
}

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