基于Netty的时间服务器程序代码
程序代码来自于《Netty权威指南》第三章，不过我都加了注释，所以看起来会非常好理解。需要注意的是，《Netty权威指南》中TimeServerHandler类继承的是ChannelHandlerAdapter，因为其使用的是Netty 5.x的版本，该版本现在已经被官方废弃，而我使用的是Netty 4.x的，所以如果继承ChannelHandlerAdapter，启动程序时不会报错，但是无法正常工作，即handler不生效这点尤其需要注意。
服务端代码
TimeServer.java:
package cn.xpleaf.netty;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;public class TimeServer { ???/** ????* 绑定端口号，启动Netty服务端 ????* @param port ????* @throws Exception ????*/ ???public void bind(int port) throws Exception { ???????// NioEventLoopGroup是个线程组，它包含了一组NIO线程，专门用于网络事件的处理 ???????// 实际上它们就是Reactor线程组，关于Reactor，这是一种设计模型， ???????// Reactor模型就是将消息放到了一个队列中，通过异步线程池对其进行消费 ???????// 在Netty中就是，NioEventLoopGroup就是Reactor，ChannelHandler就是Reactor模型中的handler ???????// 可以参考文章：http://www.ivaneye.com/2016/07/23/iomodel.html ???????// 这里创建了两个线程组，一个用于服务端接受客户端的连接，一个用于进行SocketChannel的网络读写 ???????EventLoopGroup bossGroup = new NioEventLoopGroup(); ???????EventLoopGroup workerGroup = new NioEventLoopGroup(); ???????try { ???????????// 创建NIO服务端的辅助启动类，目的是降低服务端的开发复杂度 ???????????ServerBootstrap b = new ServerBootstrap(); ???????????// 将两个NIO线程组作为参数传递到ServerBootstrap中 ???????????b.group(bossGroup, workerGroup) ???????????????// NioServerSocketChannel对应JDK NIO类库中的ServerSocketChannel ???????????????.channel(NioServerSocketChannel.class) ???????????????// 设置NioServerSocketChannel的TCP参数 ???????????????.option(ChannelOption.SO_BACKLOG, 1024) ???????????????// 绑定I/O事件的处理类ChildChannelHandler，它的作用类似于Reactor模式中的Handler类 ???????????????// 主要用于处理网络I/O事件，例如记录日志、对消息进行编解码等 ???????????????.childHandler(new ChildChannelHandler()); ???????????// 绑定端口，同步等待成功，该方法是同步阻塞的，绑定成功后返回一个ChannelFuture ???????????ChannelFuture f = b.bind(port).sync(); ???????????// 等待服务端监听端口关闭，阻塞，等待服务端链路关闭之后main函数才退出 ???????????f.channel().closeFuture().sync(); ???????} finally { ???????????// 优雅退出，释放线程池资源 ???????????bossGroup.shutdownGracefully(); ???????????workerGroup.shutdownGracefully(); ???????} ???} ???/** ????* 实现initChannel方法，其作用是当创建NioServerSocketChannel成功之后， ????* 在进行初始化是，将它的ChannelHandler设置到ChannelPipeline中，用于处理网络I/O事件 ????* @author yeyonghao ????* ????*/ ???private class ChildChannelHandler extends ChannelInitializer<SocketChannel> { ???????@Override ???????protected void initChannel(SocketChannel ch) throws Exception { ???????????ch.pipeline().addLast(new TimeServerHandler()); ???????} ???} ???public static void main(String[] args) throws Exception { ???????int port = 8080; ???????if(args != null && args.length > 0) { ???????????try { ???????????????port = Integer.valueOf(port); ???????????} catch (NumberFormatException e) { ???????????????// TODO: handle exception ???????????} ???????} ???????new TimeServer().bind(port); ???}}TimeServerHandler.java:
package cn.xpleaf.netty;import java.sql.Date;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;/** * 这里需要注意，《Netty权威指南》中TimeServerHandler类继承的是ChannelHandlerAdapter， * 因为其使用的是Netty 5.x的版本，该版本现在已经被官方废弃，而我使用的是Netty 4.x的， * 所以如果继承ChannelHandlerAdapter，启动程序时不会报错，但是无法正常工作，即handler不生效 * 这点尤其需要注意。 * @author yeyonghao * */public class TimeServerHandler extends ChannelInboundHandlerAdapter { ???/** ????* 对网络事件进行写操作 ????*/ ???@Override ???public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ???????// Netty中的ByteBuf类似于nio类库中的ByteBuffer，不过功能更强大 ???????ByteBuf buf = (ByteBuf) msg; ???????// 创建与buf一样大小的字节数组 ???????byte[] req = new byte[buf.readableBytes()]; ???????// 将数据从buf中复制到req中 ???????buf.readBytes(req); ???????String body = new String(req, "utf-8"); ???????System.out.println("The time server receive order : " + body); ???????String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? ????????????????new Date(System.currentTimeMillis()).toString() : "BAD ORDER"; ???????// 创建ByteBuf对象 ???????ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes()); ???????// 通过ChannelHandlerContext的write方法异步发送给客户端 ???????ctx.write(resp); ???} ???/** ????* 写操作完成之后进行的操作 ????*/ ???@Override ???public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ???????// ctx.write()只是将消息放到发送缓冲数组中，调用flush就将其发送缓冲区中的消息全部写到SocketChannel中 ???????ctx.flush(); ???} ???/** ????* 释放资源 ????*/ ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { ???????ctx.close(); ???}}客户端代码
TimeClient.java:
package cn.xpleaf.netty;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 void connect(int port, String host) throws Exception { ???????// 配置客户端NIO线程组 ???????EventLoopGroup group = new NioEventLoopGroup(); ???????try { ???????????// 客户端是Bootstrap，注意客户端的bootstrap只能传入一个NIO线程组 ???????????Bootstrap b = new Bootstrap(); ???????????// 客户端是NioSocketChannel ???????????b.group(group).channel(NioSocketChannel.class) ???????????????.option(ChannelOption.TCP_NODELAY, true) ???????????????// 与服务端一样的，只不过这里使用了匿名内部类 ???????????????.handler(new ChannelInitializer<SocketChannel>() { ???????????????????@Override ???????????????????protected void initChannel(SocketChannel ch) throws Exception { ???????????????????????ch.pipeline().addLast(new TimeClientHandler()); ???????????????????} ???????????????}); ???????????// 发起异步连接操作（注意服务端是bind，客户端则需要connect） ???????????ChannelFuture f = b.connect(host, port).sync(); ???????????// 等待客户端链路关闭 ???????????f.channel().closeFuture().sync(); ???????} finally { ???????????// 优雅退出，释放NIO线程组 ???????????group.shutdownGracefully(); ???????} ???} ???public static void main(String[] args) throws Exception { ???????int port = 8080; ???????if(args != null && args.length > 0) { ???????????try { ???????????????port = Integer.valueOf(port); ???????????} catch (NumberFormatException e) { ???????????????// 采用默认值 ???????????} ???????} ???????new TimeClient().connect(port, "localhost"); ???}}TimeClientHandler.java:
package cn.xpleaf.netty;import java.util.logging.Logger;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;/** * 该类的方法与功能与服务端的handler类似 * @author yeyonghao * */public class TimeClientHandler extends ChannelInboundHandlerAdapter { ???private static final Logger logger = Logger.getLogger(TimeServerHandler.class.getName()); ???private ByteBuf firstMessage; ???/** ????* 初始化需要发送的数据 ????*/ ???public TimeClientHandler() { ???????byte[] req = "QUERY TIME ORDER".getBytes(); ???????firstMessage = Unpooled.buffer(req.length); ???????firstMessage.writeBytes(req); ???} ???/** ????* 当客户端和服务端TCP链路建立成功之后，Netty的NIO线程会调用channelActive方法 ????*/ ???@Override ???public void channelActive(ChannelHandlerContext ctx) { ???????// 将请求消息发送给服务端 ???????ctx.writeAndFlush(firstMessage); ???} ???@Override ???public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ???????ByteBuf buf = (ByteBuf)msg; ???????byte[] req = new byte[buf.readableBytes()]; ???????buf.readBytes(req); ???????String body = new String(req, "utf-8"); ???????System.out.println("Now is : " + body); ???} ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ???????logger.warning("Unexpected exception from downstream : "); ???????ctx.close(); ???}}基于Netty的时间服务器程序代码
原文地址：http://blog.51cto.com/xpleaf/2070997