netty第一个程序，简单聊天程序。
server端和client端分别定义一个消息处理类
ChatServerHandler
public class ChatServerHandler extends SimpleChannelInboundHandler<String> {
private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
Channel channel = ctx.channel();
System.out.println(channel.id().asShortText()+" online");
channelGroup.writeAndFlush(channel.id().asShortText()+" online,users="+(channelGroup.size()+1));
channelGroup.add(channel);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
Channel channel = ctx.channel();
System.out.println(channel.id().asShortText()+" offline");
channelGroup.writeAndFlush(channel.id().asShortText()+" offline,users="+channelGroup.size());
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
Channel channel = ctx.channel();
channelGroup.writeAndFlush(String.format("[%s-%s]:%s",channel.id().asShortText(),LocalTime.now().withNano(0),s));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
}
使用内置基本String 类型的InboundHandler。server端维护一个ChannelGroup，当有新连接进入，触发channelActive()方法，将channel放入group中，Group.writeAndFlush()向当前所有在线连接广播新上线通知。同理有连接断开触发channelInactive()方法，group向其它在线连接发送下线通知。某个channel有新消息向当前group所有channel进行广播发送。
ChatClientHandler
public class ChatClientHandler extends SimpleChannelInboundHandler<String> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
System.out.println(s);
}
}
client端消息处理比较简单，只打印监听到服务端发送的数据。
server端启动
EventLoopGroup group = new NioEventLoopGroup(1);
ServerBootstrap boot = new ServerBootstrap();
boot.group(group).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel channel) throws Exception {
channel.pipeline()
.addLast(new StringDecoder())
.addLast(new StringEncoder())
.addLast(new ChatServerHandler());
}
});
System.out.println("server start");
ChannelFuture future = boot.bind(8888).sync();
future.channel().closeFuture().sync();
group.shutdownGracefully();
绑定线程组、消息处理类及服务端口。消息处理类绑定了上面定义的ChatServerHandler，另外还有两个字符串编码解码内置处理类。编解码先理解下就是流数据都使用字符串字节解析，还没定义报文格式。
client端启动
EventLoopGroup group = new NioEventLoopGroup();
Bootstrap boot = new Bootstrap();
boot.group(group).channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel channel) throws Exception {
channel.pipeline().addLast(new StringEncoder())
.addLast(new StringDecoder())
.addLast(new ChatClientHandler());
}
});
ChannelFuture future = boot.connect("localhost", 8888).sync();
Channel channel = future.channel();
//channel.writeAndFlush("hi");
Scanner scanner = new Scanner(System.in);
while (scanner.hasNextLine()) {
String msg = scanner.nextLine();
channel.writeAndFlush(msg);
}
channel.closeFuture().sync();
group.shutdownGracefully();
绑定线程组，handler处理类，连接server端端口。使用Scanner读取console输入，发送内容数据。