package me.test.jdk.java.nio;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class NioEchoServer {
public static void main(String[] args) {
new Thread(new Manager()).start();
}
/**
* Start server, regist Selector, loop selector and dispatch msg.
*/
private static class Manager implements Runnable {
private ExecutorService exec = null;
@Override
public void run() {
try {
ServerSocketChannel channel = ServerSocketChannel.open();
channel.configureBlocking(false);
channel.socket().bind(new InetSocketAddress("localhost", 9999));
Selector selector = Selector.open();
channel.register(selector, SelectionKey.OP_ACCEPT);
while (true) {
// blocking for accept
selector.select();
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while (it.hasNext()) {
SelectionKey curKey = it.next();
it.remove();
System.out.println(curKey
+ ": valid = " + curKey.isValid()
+ ", acceptable = " + curKey.isAcceptable()
+ ", connectable = " + curKey.isConnectable()
+ ", readable = " + curKey.isReadable()
+ ", writeable = " + curKey.isWritable()
);
if (!curKey.isValid()) {
continue;
}
if (curKey.isAcceptable()) {
accept(curKey);
} else if (curKey.isReadable()) {
read(curKey);
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
private void accept(SelectionKey key) throws IOException {
ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
SocketChannel clientChannel = serverChannel.accept();
clientChannel.configureBlocking(false);
clientChannel.register(key.selector(), SelectionKey.OP_READ);
System.out.println("accept connection : " + clientChannel.socket());
}
@SuppressWarnings({ "rawtypes", "unchecked" })
private void read(SelectionKey curKey) {
// 当有消息时，需要直到构建一个完整的业务数据封包（这里是一个UTF-8编码的单个字符），才传递个一个新的Worker进行处理。
SocketChannel clientChannel = (SocketChannel) curKey.channel();
try {
// CASE1：断开连接
if (!clientChannel.isConnected()) {
clientChannel.close();
System.out.println("when read, closed.");
} else if (!clientChannel.isOpen()) {
System.out.println("when read, closed.");
} else {
SelectionKey regKey = clientChannel.keyFor(curKey.selector());
Map holders = (Map) regKey.attachment();
ByteBuffer byteBuf;
CharBuffer charBuf;
CharsetDecoder cd;
if (holders == null) {
holders = new HashMap();
byteBuf = ByteBuffer.allocate(32);
holders.put("byteBuf", byteBuf);
charBuf = CharBuffer.allocate(2);
holders.put("charBuf", charBuf);
cd = StandardCharsets.UTF_8
.newDecoder()
// .onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE);
holders.put("cd", cd);
regKey.attach(holders);
} else {
byteBuf = (ByteBuffer) holders.get("byteBuf");
charBuf = (CharBuffer) holders.get("charBuf");
cd = (CharsetDecoder) holders.get("cd");
}
// 该一回合，可能只读取到部分数据。不能尝试直到读取完毕所有数据，
// 否则，若client持续不断的发送数据，则会因此线程一直占有而无法为其他Client提供服务。
int i = clientChannel.read(byteBuf);
if (i != 0) {
byteBuf.flip();
// 将 byte[] 按照UTF-8的编码解析为一个个字符
while (true) {
charBuf.clear();
CoderResult cr = cd.decode(byteBuf, charBuf, i == -1 ? true : false);
System.out.println("i = " + i
+ ", cr " + cr
+ ", byteBuf=" + byteBuf
+ ", charBuf=" + charBuf);
if (cr.isMalformed()) {
byteBuf.position(byteBuf.position() + cr.length());
charBuf.put(cd.replacement());
}
// CASE3：正常读取
if (charBuf.position() > 0) {
charBuf.flip();
if (exec == null) {
exec = new ThreadPoolExecutor(1, 2, 1, TimeUnit.MINUTES,
new LinkedBlockingQueue<Runnable>());
}
for (int j = 0; j < charBuf.limit(); j++) {
exec.execute(new Worker(charBuf.get(j), clientChannel));
// new Worker(charBuf.get(j), clientChannel).run();
}
}
if (!cr.isError()) {
break;
}
}
byteBuf.compact();
}
// CASE2：到达流的末尾？？？可能么？
if (i == -1) {
if (clientChannel.isConnected()) {
clientChannel.close();
System.out.println("when read, reach end, closing.");
}
}
}
} catch (IOException e) {
if (clientChannel.isConnected()) {
try {
clientChannel.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
e.printStackTrace();
}
}
}
/**
* 可以当作一个Servlet、Action、Controller etc。 处理一次用户消息。
*/
private static class Worker implements Runnable {
private SocketChannel channel;
private char c;
/**
* 将指定的字符返回给客户端。
*
* @param c
* 一个字符。真实场景下可能是一个业务数据封包。之后可能会做很多耗时、耗资源的操作。
* @param channel
*/
public Worker(char c, SocketChannel channel) {
this.c = c;
this.channel = channel;
}
@Override
public void run() {
try {
if ('.' == c) {
System.out.println("read terminal command '.' : closing.~~" + channel.socket() + "\n");
// 要关闭socket，否则会Client不会会一直等下去。
channel.socket().close();
channel.close();
} else {
channel.write(ByteBuffer.wrap(String.valueOf(c).getBytes("UTF-8")));
System.out.println(">>> '" + c + "'");
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}