使用netty进行客户端网络编程及断线重连功能实现

本文主要是介绍使用netty进行客户端网络编程及断线重连功能实现，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

       当用netty进行客户端网络编程时，与服务端建立连接并完成数据编码、解码、通信是最基础功能，考虑程序的健壮性，则断线重连是必不可少的一个功能点。netty源码的example文件夹中uptime目录中有相关示例demo，但是总觉得该样例代码封装的不够好，于是决定自己动手重新写一个，如果有更优雅的断线重连实现方法，希望大家将链接留言发我。下面是主体代码，Handler部分就不分享了。

public class BaseClient implements Runnable {private static Logger LOGGER = LoggerTools.getInstance(BaseClient.class);private String host_;private int port_;private int reConnectCount_ = 0;private ClientHandler clientHandler_;private OnMessageListener messageListener_;private OnStartupListener startupListener_;private volatile boolean isChannelPrepared_;private final static int MAX_MESSAGE_LENGTH = 8192;public BaseClient(String host, int port, OnMessageListener messageListener, OnStartupListener startupListener) {host_ = host;port_ = port;messageListener_ = messageListener;startupListener_ = startupListener;}@Overridepublic void run() {connect(host_, port_);}// 发送消息public void sendMessage(String msg, ResultListener<String> listener) {if (isChannelPrepared_) {clientHandler_.sendMessage(msg, listener);} else {listener.onFailure(msg);LOGGER.error("连接还未建立, 无法发送数据...");}}// 建立连接private void connect(String host, int port) {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap b = new Bootstrap();b.group(group);b.channel(NioSocketChannel.class);b.option(ChannelOption.TCP_NODELAY, true);b.handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline p = ch.pipeline();p.addLast(new LengthFieldBasedFrameDecoder(MAX_MESSAGE_LENGTH, 0, 4, 0 ,4));p.addLast(new LengthFieldPrepender(4));p.addLast(new StringDecoder(CharsetUtil.UTF_8));p.addLast(new StringEncoder(CharsetUtil.UTF_8));clientHandler_ = new ClientHandler(messageListener_);p.addLast(clientHandler_);}});ChannelFuture f = b.connect(host, port).sync();f.addListener(new GenericFutureListener<Future<? super Void>>() {@Overridepublic void operationComplete(Future<? super Void> future) throws Exception {if (future.isSuccess()) {reConnectCount_ = 0;isChannelPrepared_ = true;startupListener_.onCompletion(true);LOGGER.info("与服务器{}:{}连接建立成功...", host_, port_);} else {isChannelPrepared_ = false;startupListener_.onCompletion(false);LOGGER.info("与服务器{}:{}连接建立失败...", host_, port_);}}});f.channel().closeFuture().sync();} catch (Exception e) {isChannelPrepared_ = false;LOGGER.error("与服务器{}:{}连接出现异常...", host_, port_);} finally {isChannelPrepared_ = false;group.shutdownGracefully();reConnect(host, port);}}// 断线重连private void reConnect(String host, int port) {// fixme: 重连显式退出?try {isChannelPrepared_ = false;int delay = ++reConnectCount_ * 5;reConnectCount_ = reConnectCount_ > 23 ? 23 : reConnectCount_;LOGGER.error("与服务器{}:{}连接已断开, {}秒后重连...", host, port, delay);Thread.sleep(delay * 1000);connect(host, port);} catch (Exception e) {e.printStackTrace();}}}

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