1、开发spring boot微服务中，需要和第三方服务器做报文交换数据，用netty来实现客户端，并做一个同步接受数据。一下用的是netty5，其它版本的相似即可。

2、pom.xml引入

        <dependency>
		<groupId>io.netty</groupId>
		<artifactId>netty-all</artifactId>
		<version>5.0.0.Alpha1</version>
	</dependency>

3、ClientInitializer编写

import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.timeout.ReadTimeoutHandler;
public class ClientInitializer extends ChannelInitializer<SocketChannel>{
	private CountDownLatch lathc;
	public ClientInitializer(CountDownLatch lathc) {
		this.lathc = lathc;
	}
	private ClientHandler handler;
	@Override
	protected void initChannel(SocketChannel sc) throws Exception {
		handler =  new ClientHandler(lathc);
		sc.pipeline().addLast(new StringDecoder());//进行字符串的编解码设置
		sc.pipeline().addLast(new StringEncoder());
		sc.pipeline().addLast(new ReadTimeoutHandler(60));//设置超时时间
		sc.pipeline().addLast(handler);
	}
	public String getServerResult(){
        return handler.getResult();
    }
    public void resetLathc(CountDownLatch lathc) {
        handler.resetLatch(lathc);
    }

}

4、ClientHandler编码实现

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import java.util.concurrent.CountDownLatch;
public class ClientHandler extends ChannelHandlerAdapter{
	
	private CountDownLatch lathc;
	private String result;
	public ClientHandler(CountDownLatch lathc) {
        this.lathc = lathc;
        }
	
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {

	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) {
		result = (String) msg;
		lathc.countDown();// 消息接收后释放同步锁，lathc是从Client加一传回来的
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		ctx.close();
	}
	public void resetLatch(CountDownLatch lathc) {
		this.lathc = lathc;
	}

	public String getResult() {
		return result;
	}

	
}

5、Client端运行主程序编写

import java.util.concurrent.CountDownLatch;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;;
public class Client {//编写客户端单例模式方便系统调用
	private static class SingletonHolder {
		static final Client instance = new Client();
	}
	public static Client getInstance(){
		return SingletonHolder.instance;
	}
	private EventLoopGroup group;
	private Bootstrap b;
	private ChannelFuture cf ;
	private ClientInitializer clientInitializer;
	private CountDownLatch lathc;
	private Client(){
		    lathc = new CountDownLatch(0);
		    clientInitializer = new ClientInitializer(lathc);
			group = new NioEventLoopGroup();
			b = new Bootstrap();
			b.group(group)
			 .channel(NioSocketChannel.class)
			 .handler(clientInitializer);
	}
	public void connect(){
		//192.168.43.51测试端口8766 192.168.43.102 线上端口8765
		try {
			this.cf = b.connect("127.0.01", 8888).sync();
			System.out.println("远程服务器已经连接, 可以进行数据交换..");
		} catch (InterruptedException e) {
			e.printStackTrace();
		} finally {
		}
	}
	public ChannelFuture getChannelFuture(){
		if(this.cf == null) {
			this.connect();
		}
		if(!this.cf.channel().isActive()){
			this.connect();
		}
		return this.cf;
	}
	public void close(){
		try {
			this.cf.channel().closeFuture().sync();
			this.group.shutdownGracefully();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	 public String setMessage(String msg) throws InterruptedException{
	    	ChannelFuture cf =getInstance().getChannelFuture();//单例模式获取ChannelFuture对象
	    	cf.channel().writeAndFlush(msg);
	    	//发送数据控制门闩加一
	    	lathc = new CountDownLatch(1);
	        clientInitializer.resetLathc(lathc);
	        lathc.await();//开始等待结果返回后执行下面的代码
	        return clientInitializer.getServerResult();
	  }
	 public static void main(String[] args) throws Exception {
	    System.out.println(Client.getInstance().setMessage("123"));//测试等待数据返回
	 }
}

6、以上代码完整，直接复制粘贴即可使用

欢迎大家有问题和意见可以留言