netty2 案例:数据通信

在实际的项目中应该如何使用netty去通信呢？

一般来说，会有以下三种情况，

1长连接 也就是服务器和客户端的通道一直不关闭，如果服务器性能非常好，并且在客户端数量不是很多的情况下，可以选择使用这种方式。

2短连接  一次性批量提交数据，我们可能会吧我们的数据保存在数据库中，比如1个小时提交提交一次。这种做法的弊端是不能够实时传输，实时性要求不高的情况可以推荐使用

3一种特殊的长连接 在特定时间的内，如果服务器和客服端没有通讯 就断开连接 下次当客户端需要再次发送数据的时候，再次连接 。但是这种方式我们需要考虑？

1连接超时以后我们如何断开连接？ 而在需要发送数据的时候我们怎么再次连接？

2服务器宕机了怎么办？

1连接超时以后我们如何断开连接？（在netty中可以通过ReadTimeoutHandler类实现超过多长时间断开连接）

而在需要发送数据的时候我们怎么再次连接？

（我们可以封装一个方法 调用该方法就可以获得连接）

2服务器宕机了怎么办？

生产环境我们一般会部署netty集群，结合zookeeper完成。

下面我用代码演示一下

Server端口变化不大 ，主要是客户端

Server端代码

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.timeout.ReadTimeoutHandler;

public class Server {
	public static void main(String[] args) throws Exception {
		//
		EventLoopGroup bossGroup = new NioEventLoopGroup();

		EventLoopGroup workGroup = new NioEventLoopGroup();

		ServerBootstrap bootStrap = new ServerBootstrap();

		bootStrap.group(bossGroup, workGroup).channel(NioServerSocketChannel.class)
				.childHandler(new ChannelInitializer<SocketChannel>() {

					@Override
					protected void initChannel(SocketChannel sc) throws Exception {
//						ByteBuf delimiters = Unpooled.copiedBuffer("$".getBytes()) ;
//						sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiters ));
//						sc.pipeline().addLast(new StringDecoder());
						sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
						sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
						sc.pipeline().addLast(new ReadTimeoutHandler(5));//超时时间设置
						sc.pipeline().addLast(new ServerHandler());
					}
				});
		ChannelFuture f = bootStrap.bind(8888).sync();
		ChannelFuture f1 = bootStrap.bind(9999).sync();
        //服务器一直不关闭
		f.channel().closeFuture().sync();
		f1.channel().closeFuture().sync();
		bossGroup.shutdownGracefully();
		workGroup.shutdownGracefully();
	}

}

　　

import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class ServerHandler extends ChannelHandlerAdapter {

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

			System.out.println("server " + msg);
			Data data = new Data();
			data.setId(1);
			data.setName("server replay");
			// 写操作完成以后就断开连接
			ctx.writeAndFlush(data).addListener(ChannelFutureListener.CLOSE);

	}

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

}

　　序列化工具代码 这里使用jboss的Marshalling

import io.netty.handler.codec.marshalling.DefaultMarshallerProvider;
import io.netty.handler.codec.marshalling.DefaultUnmarshallerProvider;
import io.netty.handler.codec.marshalling.MarshallerProvider;
import io.netty.handler.codec.marshalling.MarshallingDecoder;
import io.netty.handler.codec.marshalling.MarshallingEncoder;
import io.netty.handler.codec.marshalling.UnmarshallerProvider;

import org.jboss.marshalling.MarshallerFactory;
import org.jboss.marshalling.Marshalling;
import org.jboss.marshalling.MarshallingConfiguration;

public final class MarshallingCodeCFactory {

	public static MarshallingDecoder buildMarshallingDecoder() {
    	//首先通过Marshalling工具类的精通方法获取Marshalling实例对象 参数serial标识创建的是java序列化工厂对象。
		final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
		//创建了MarshallingConfiguration对象，配置了版本号为5
		final MarshallingConfiguration configuration = new MarshallingConfiguration();
		configuration.setVersion(5);
		//根据marshallerFactory和configuration创建provider
		UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
		//构建Netty的MarshallingDecoder对象，俩个参数分别为provider和单个消息序列化后的最大长度
		MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024);
		return decoder;
    }

    public static MarshallingEncoder buildMarshallingEncoder() {
		final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
		final MarshallingConfiguration configuration = new MarshallingConfiguration();
		configuration.setVersion(5);
		MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
		//构建Netty的MarshallingEncoder对象，MarshallingEncoder用于实现序列化接口的POJO对象序列化为二进制数组
		MarshallingEncoder encoder = new MarshallingEncoder(provider);
		return encoder;
    }
}

　　================

一个简单的实体类 （Data）

import java.io.Serializable;

public class Data implements Serializable{
	/**
	 *
	 */
	private static final long serialVersionUID = -963211196207628767L;
	private Integer id;
	private String name;

	@Override
	public String toString() {
		return " [id=" + id + ", name=" + name + "]";
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

}

　　==================================================================================================

以下是客户端代码

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

public class Client {
	EventLoopGroup workGroup = null;
	Bootstrap bootstrap = null;
	ChannelFuture channelFuture = null;

	private static class ClientFactory {
		private static Client instance = new Client();
	}

	public static Client getClientInstance() {
		return ClientFactory.instance;
	}

	private Client() {
		// 数理化相关对象
		workGroup = new NioEventLoopGroup();
		bootstrap = new Bootstrap();
		bootstrap.group(workGroup).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {

			@Override
			protected void initChannel(SocketChannel sc) throws Exception {
				// ByteBuf delimiters = Unpooled.copiedBuffer("$".getBytes()) ;
				// sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,
				// delimiters ));
				// sc.pipeline().addLast(new StringDecoder());
				sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
				sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
				sc.pipeline().addLast(new ReadTimeoutHandler(5));
				sc.pipeline().addLast(new ClientHandler());
			}
		});
	}

	public void connect() {
		try {
			this.channelFuture = bootstrap.connect("127.0.0.1", 9999).sync();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	public ChannelFuture getChannelFuture() {
		if (this.channelFuture == null) {
			this.connect();
		}
		if (!this.channelFuture.channel().isActive()) {
			this.connect();
		}
		return this.channelFuture;
	}

	public static void main(String[] args) throws Exception {

		final Client client = getClientInstance();
		client.connect();
		ChannelFuture cf = client.getChannelFuture();
		Data data = new Data();
		data.setId(1);
		data.setName("first");
		cf.channel().writeAndFlush(data);
		Thread.sleep(6000);
		//因为设置的5秒超时 这里通过一个子线程 模拟再次连接
		new Thread(new Runnable() {
			public void run() {
				System.out.println("进入子线程...");
				ChannelFuture cf = client.getChannelFuture();
				Data data = new Data();
				data.setId(2);
				data.setName("second");
				cf.channel().writeAndFlush(data);
				try {
					cf.channel().closeFuture().sync();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				System.out.println("子线程结束！！");
			}
		}).start();
		cf.channel().closeFuture().sync();

		System.out.println("主线程结束!!");
	}
}

　　

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.ReferenceCountUtil;

public class ClientHandler extends ChannelHandlerAdapter {

	/**
	 * 通道刚刚建立的时候 发送认证消息 （认证通过 建立连接 失败 关闭连接）
	 */
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		// TODO Auto-generated method stub
	//	ctx.channel().writeAndFlush("发送认证消息");
		super.channelActive(ctx);
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		try {
			//do something msg
			System.out.println("Client: " + (Data)msg);
		} finally {
			ReferenceCountUtil.release(msg);
		}
	}

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

　　一下是运行结果

服务器端

客户端