一起养成写作习惯！这是我参与「掘金日新计划 · 4 月更文挑战」的第1天，点击查看活动详情。
背景
- 整理网络编程的基本写法（IO 、NIO、Netty）。
IO服务端
public static void main(String[] args) throws IOException {
ExecutorService pool = Executors.newCachedThreadPool();
ServerSocket serverSocket = new ServerSocket(8899);
while(true) {
final Socket socket = serverSocket.accept();
pool.execute(new Runnable() {
@Override
public void run() {
byte[] bytes = new byte[1024];
try {
InputStream inputStream = socket.getInputStream();
int read = inputStream.read(bytes);
// todo 业务逻辑
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
}
NIO服务端
private static Map<String, SocketChannel> clientMap = new HashMap();
public static void main(String[] args) throws Exception{
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);//非阻塞
ServerSocket serverSocket = serverSocketChannel.socket();
serverSocket.bind(new InetSocketAddress(8899));
Selector selector = Selector.open();
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
while (true) {
try {
selector.select();
Set<SelectionKey> selectionKeys = selector.selectedKeys();
selectionKeys.forEach(selectionKey -> {
final SocketChannel client;
try{
if (selectionKey.isAcceptable()) {
ServerSocketChannel server = (ServerSocketChannel) selectionKey.channel();
client = server.accept();
client.configureBlocking(false);
client.register(selector, SelectionKey.OP_READ);
String key = "【" + UUID.randomUUID().toString() + "】";
clientMap.put(key, client);
} else if (selectionKey.isReadable()) {
client = (SocketChannel)selectionKey.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int count = client.read(readBuffer);
if (count > 0) {
readBuffer.flip();
Charset charset = Charset.forName("utf-8");
String receivedMessage = String.valueOf(charset.decode(readBuffer).array());
System.out.println(client + ": " + receivedMessage);
String senderKey = null;
for(Map.Entry<String, SocketChannel> entry : clientMap.entrySet()) {
if (client == entry.getValue()) {
senderKey = entry.getKey();
break;
}
}
for(Map.Entry<String, SocketChannel> entry: clientMap.entrySet()) {
SocketChannel value = entry.getValue();
ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
writeBuffer.put((senderKey + ": " + receivedMessage).getBytes());
writeBuffer.flip();
value.write(writeBuffer);
}
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
});
selectionKeys.clear();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
NIO客户端
public static void main(String[] args) throws Exception {
try{
SocketChannel socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
Selector selector = Selector.open();
socketChannel.register(selector, SelectionKey.OP_CONNECT);
socketChannel.connect(new InetSocketAddress("127.0.0.1",8899));
while (true) {
selector.select();
Set<SelectionKey> keySet = selector.selectedKeys();
for (SelectionKey selectionKey: keySet) {
if (selectionKey.isConnectable()) {
SocketChannel client = (SocketChannel)selectionKey.channel();
if (client.isConnectionPending()) {
client.finishConnect();
ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
writeBuffer.put((LocalDateTime.now() + " Connected!").getBytes());
writeBuffer.flip();
client.write(writeBuffer);
ExecutorService executorService = Executors.newSingleThreadExecutor(Executors.defaultThreadFactory());
executorService.submit(() -> {
try {
writeBuffer.clear();
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(input);
String sendMessage = br.readLine();
writeBuffer.put(sendMessage.getBytes());
writeBuffer.flip();
client.write(writeBuffer);
} catch (Exception ex) {
ex.printStackTrace();
}
});
}
client.register(selector, SelectionKey.OP_READ);
} else if (selectionKey.isReadable()) {
SocketChannel client = (SocketChannel)selectionKey.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int count = client.read(readBuffer);
if (count > 0) {
String receivedMessage = new String(readBuffer.array(), 0, count);
System.out.println(receivedMessage);
}
}
}
keySet.clear();
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
Netty服务端
- MyServer
public class MyServer {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workGroup = new NioEventLoopGroup();
try{
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workGroup).channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.WARN))
.childHandler(new MyServerInitalizer());
ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
channelFuture.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workGroup.shutdownGracefully();
}
}
}
- MyServerInitalizer
public class MyServerInitalizer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
//Netty自己提供的基础组件
pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
pipeline.addLast(new LengthFieldPrepender(4));
pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
//开发者自定义的handler
pipeline.addLast("my server handler: ", new MyServerHandler());
}
}
- MyHandler
public class MyServerHandler extends SimpleChannelInboundHandler<String> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println(ctx.channel().remoteAddress() + ", " + msg);
ctx.channel().writeAndFlush("from server: " + UUID.randomUUID());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
Netty客户端
- MyClient
public class MyClient {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try{
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class).handler(new MyClientInitalizer());
ChannelFuture channelFuture = bootstrap.connect("localhost", 8899).sync();
channelFuture.channel().closeFuture().sync();
} finally {
eventLoopGroup.shutdownGracefully();
}
}
}
- MyClientInitalizer
public class MyClientInitalizer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
//Netty自己提供的基础组件
pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
pipeline.addLast(new LengthFieldPrepender(4));
pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
pipeline.addLast(new MyClientHandler());
}
}
- MyClientHandler
public class MyClientHandler extends SimpleChannelInboundHandler<String> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println(ctx.channel().remoteAddress());
System.out.println("client output: " + msg);
ctx.writeAndFlush("from client: " + LocalDateTime.now());
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ctx.writeAndFlush("Hello, How's it going!");
super.channelActive(ctx);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
.
小结
-
整理网络编程的演讲过程。
-
Netty与NIO类比
Netty的NioEventLoopGroup相当于 NIO的 Selector
Netty的ServerSocketChannel相当于 NIO的channle
Netty的ByteBuf相当于NIO的ByteBuffer
