Netty 5 官网例子

Netty 提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。

体系结构图

官网中整合代码块之后的完整例子。

TimeDecoder.java

import io.netty.buffer.ByteBuf;

import io.netty.channel.ChannelHandlerContext;

import io.netty.handler.codec.ByteToMessageDecoder;

import java.util.List;

public class TimeDecoder extends ByteToMessageDecoder { // (1)
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { // (2)
        if (in.readableBytes() < 4) {
            return; // (3)
        }

//        out.add(in.readBytes(4)); // (4)
        out.add(new UnixTime(in.readInt()));
    }
}

TimeEncoder.java　　

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;

public class TimeEncoder extends ChannelHandlerAdapter {
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
        UnixTime m = (UnixTime) msg;
        ByteBuf encoded = ctx.alloc().buffer(4);
        encoded.writeInt(m.value());
        ctx.write(encoded, promise); // (1) 
    }
}

　　TimeServerHandler.java

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class TimeServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(final ChannelHandlerContext ctx) { // (1)
        final ByteBuf time = ctx.alloc().buffer(4); // (2)
        time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));

        final ChannelFuture f = ctx.writeAndFlush(time); // (3)
        f.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) {
                assert f == future;
                ctx.close();
            }
        }); // (4)
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

　　UnixTime.java

import java.util.Date;

public class UnixTime {

    private final int value;

    public UnixTime() {
        this((int) (System.currentTimeMillis() / 1000L + 2208988800L));
    }

    public UnixTime(int value) {
        this.value = value;
    }

    public int value() {
        return value;
    }

    @Override
    public String toString() {
        return new Date((value() - 2208988800L) * 1000L).toString();
    }
}

　　TimeClientHandler.java

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

import java.util.Date;

public class TimeClientHandler extends ChannelHandlerAdapter {
	private ByteBuf buf;

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) {
        buf = ctx.alloc().buffer(4); // (1)
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) {
        buf.release(); // (1)
        buf = null;
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ByteBuf m = (ByteBuf) msg;
        buf.writeBytes(m); // (2)
        m.release();

        if (buf.readableBytes() >= 4) { // (3)
            long currentTimeMillis = (buf.readInt() - 2208988800L) * 1000L;
            System.out.println(new Date(currentTimeMillis));
            ctx.close();
        }
    }
    
//    @Override
//    public void channelRead(ChannelHandlerContext ctx, Object msg) {
//        UnixTime m = (UnixTime) msg;
//        System.out.println(m);
//        ctx.close();
//    }

//    @Override
//    public void channelRead(ChannelHandlerContext ctx, Object msg) {
//        ByteBuf m = (ByteBuf) msg; // (1)
//        try {
//            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;
//            System.out.println(new Date(currentTimeMillis));
//            ctx.close();
//        } finally {
//            m.release();
//        }
//    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

　　DiscardServerHandler.java

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

/**
 * Handles a server-side channel.
 */
public class DiscardServerHandler extends ChannelHandlerAdapter { // (1)

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)
        // Discard the received data silently.
        ((ByteBuf) msg).release(); // (3)
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

 

Application　　

 

---

DiscardServer.java

 

import io.netty.bootstrap.ServerBootstrap;

import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * Discards any incoming data.
 */
public class DiscardServer {

	private int port;

	public DiscardServer(int port) {
		this.port = port;
	}

	public void run() throws Exception {
		EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap b = new ServerBootstrap(); // (2)
			b.group(bossGroup, workerGroup)
					.channel(NioServerSocketChannel.class) // (3)
					.childHandler(new ChannelInitializer<SocketChannel>() { // (4)
								@Override
								public void initChannel(SocketChannel ch)
										throws Exception {
									ch.pipeline().addLast(
											new DiscardServerHandler());
								}
							}).option(ChannelOption.SO_BACKLOG, 128) // (5)
					.childOption(ChannelOption.SO_KEEPALIVE, true); // (6)

			// Bind and start to accept incoming connections.
			ChannelFuture f = b.bind(port).sync(); // (7)

			// Wait until the server socket is closed.
			// In this example, this does not happen, but you can do that to
			// gracefully
			// shut down your server.
			f.channel().closeFuture().sync();
		} finally {
			workerGroup.shutdownGracefully();
			bossGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws Exception {
		int port;
		if (args.length > 0) {
			port = Integer.parseInt(args[0]);
		} else {
			port = 8080;
		}
		new DiscardServer(port).run();
	}
}

TimeClient.java

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class TimeClient {
    public static void main(String[] args) throws Exception {
        String host = "";
        int port;
        if (args.length > 0) {
        	host = args[0];
            port = Integer.parseInt(args[1]);
        } else {
        	host = "127.0.0.1";
            port = 8080;
        }
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            Bootstrap b = new Bootstrap(); // (1)
            b.group(workerGroup); // (2)
            b.channel(NioSocketChannel.class); // (3)
            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new TimeClientHandler());
                }
            });

            // Start the client.
            ChannelFuture f = b.connect(host, port).sync(); // (5)

            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}