Netty 学习(2)

Netty通信案例
本文介绍了一个使用Netty实现的客户端与服务器之间的通信案例。通过定义Person类作为传输的数据类型,并自定义编解码器实现对象的序列化和反序列化过程。该案例展示了如何在Netty中设置客户端和服务端的管道工厂,以及如何处理连接和消息接收。


package yang.netty.test;

import static org.jboss.netty.buffer.ChannelBuffers.dynamicBuffer;

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFactory;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.frame.FrameDecoder;

class Persons {
	private String name;
	private int age;
	private double salary;

	public Persons(String name, int age, double salary) {
		this.name = name;
		this.age = age;
		this.salary = salary;
	}

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public double getSalary() {
		return salary;
	}

	public void setSalary(double salary) {
		this.salary = salary;
	}

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

class TimeClientHandler extends SimpleChannelHandler {

	@Override
	public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e)
			throws Exception {
		Persons person = new Persons("杨少飞", 24, 8888.88);
		e.getChannel().write(person);
		System.out.println("Send Message: " + person);
	}
	
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
		System.out.println("Unexpected exception from downstream."
				+ e.getCause());
		e.getChannel().close();
	}
}

class  TimeServerHandler extends SimpleChannelHandler {

	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
			throws Exception {
		Persons person = (Persons) e.getMessage();
		System.out.println("Recevied Message: " + person);
//		System.out.println("e.message: " + e.getMessage());
//		System.out.println("e.channel: " + e.getChannel());
//		System.out.println("e.RemoteAddress: " + e.getRemoteAddress());
	}
	
	public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
		System.out.println("Unexpected exception from upstream."
				+ e.getCause());
		e.getChannel().close();
	}
}

class TimeDecoder extends FrameDecoder {
	private final ChannelBuffer buffer = dynamicBuffer();//默认256

	@Override
	protected Object decode(ChannelHandlerContext ctx, Channel channel,
			ChannelBuffer channelBuffer) throws Exception {
		
		 System.out.println("Decode Method");
//		System.out.println("channelBuffer bytes: " + channelBuffer.readableBytes());
		if (channelBuffer.readable()) {
			//将channelBuffer中的数据转移的buffer中
			channelBuffer.readBytes(buffer, channelBuffer.readableBytes());
		}
//		System.out.println("readable bytes: " + buffer.readableBytes( ));
//        System.out.println("readable index: " + buffer.readerIndex( ));
//        System.out.println("writable bytes: " + buffer.writableBytes( ));
//        System.out.println("writable index: " + buffer.writerIndex( ));
        
		int namelength = buffer.readInt();
		String name = new String(buffer.readBytes(namelength).array(), "GBK");
		int age = buffer.readInt();
		double salary = buffer.readDouble();
		Persons person = new Persons(name, age, salary);
		return person;
	}

}

class TimeEncoder extends SimpleChannelHandler {
	private final ChannelBuffer buffer = dynamicBuffer();

	@Override
	public void writeRequested(ChannelHandlerContext ctx, MessageEvent e)
			throws Exception {
		 System.out.println("Encode Method");
		 
		Persons person = (Persons) e.getMessage();
		buffer.writeInt(person.getName().getBytes("GBK").length);//4
		buffer.writeBytes(person.getName().getBytes("GBK"));//6
		buffer.writeInt(person.getAge());//4
		buffer.writeDouble(person.getSalary());//8
		Channels.write(ctx, e.getFuture(), buffer);
	}
}

public class TestCase2 {
	public static void testServer() {
		ChannelFactory factory = new NioServerSocketChannelFactory(
				Executors.newCachedThreadPool(),
				Executors.newCachedThreadPool());
		ServerBootstrap bootstrap = new ServerBootstrap(factory);
		bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
			public ChannelPipeline getPipeline() throws Exception {
				ChannelPipeline pipeline = Channels.pipeline();
				pipeline.addLast("decoder", new TimeDecoder());
				pipeline.addLast("encoder", new TimeEncoder());
				pipeline.addLast("handler", new TimeServerHandler());
				return pipeline;
			}
		});
		bootstrap.setOption("child.tcpNoDelay", true);
		bootstrap.setOption("child.keepAlive", true);
		bootstrap.bind(new InetSocketAddress("localhost", 3333));
		System.out.println("Server is on ....");
	}

	public static void testClient() {
		// 创建客户端channel的辅助类,发起connection请求
		ClientBootstrap bootstrap = new ClientBootstrap(
				new NioClientSocketChannelFactory(
						Executors.newCachedThreadPool(),
						Executors.newCachedThreadPool()));
		bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
			public ChannelPipeline getPipeline() {
				ChannelPipeline pipeline = Channels.pipeline();
				pipeline.addLast("decoder", new TimeDecoder());
				pipeline.addLast("encoder", new TimeEncoder());
				pipeline.addLast("handler", new TimeClientHandler());
				return pipeline;
			}
		});
		
		/*
		 bbootstrap.setPipelineFactory(new MyPipelineFactory());
		 public class MyPipelineFactory implements ChannelPipelineFactory {
		   public ChannelPipeline getPipeline() throws Exception {
		     // Create and configure a new pipeline for a new channel.
		     ChannelPipeline p = Channels.pipeline();
		     p.addLast("encoder", new EncodingHandler());
		     p.addLast("decoder", new DecodingHandler());
		     p.addLast("logic",   new LogicHandler());
		     return p;
		   }
		 }
		 */
		
		ChannelFuture future = bootstrap.connect(new InetSocketAddress(
				"localhost", 3333));
		System.out.println("Client is on ....");
		future.getChannel().getCloseFuture().awaitUninterruptibly();
		bootstrap.releaseExternalResources();
	}

	public static void main(String[] argv) {
		testServer();
		testClient();
	}
}

运行结果

Server is on ....
Client is on ....
Encode Method
Send Message: Persons [name=杨少飞, age=24, salary=8888.88]
Decode Method
Recevied Message: Persons [name=杨少飞, age=24, salary=8888.88]


### Netty 学习教程与入门指南 #### 什么是NettyNetty是一个基于NIO的客户、服务器端编程框架,提供了异步的、事件驱动的网络应用程序框架和工具,可以快速开发高可用的客户端和服务器[^3]。 #### Netty的核心组件 以下是Netty中的核心组件及其作用: - **EventLoop**: 负责处理I/O操作以及执行注册到其上的任务。 - **Channel**: 表示一个连接,用于读写数据。 - **Future**: 提供了一种机制来获取异步操作的结果。 - **Pipeline & Handler**: 处理链模式实现请求响应流程控制。`Pipeline`是一系列`Handler`组成的链条,负责拦截并处理消息流。 - **ByteBuf**: 更加高效灵活的字节容器替代传统的`ByteBuffer`[^1]。 #### Netty的主要优势 1. **API简单易用**:相比原始的Java NIO API,Netty封装了许多复杂细节,降低了开发难度。 2. **强大的功能支持**:内置多种编解码器和支持主流协议的功能模块。 3. **高度可定制化**:开发者可通过自定义`ChannelHandler`扩展通信逻辑。 4. **卓越性能表现**:经过大量测试表明,在相同条件下,Netty比其他NIO框架具有更高的吞吐量和更低延迟。 5. **稳定性强**:修复了已知的所有JDK NIO缺陷,并广泛应用于多个领域如Hadoop RPC框架Avro等实际生产环境中[^4]。 #### 初学者的第一个Netty Demo ("Hello World") 为了帮助理解如何使用Netty创建基本的应用程序,这里给出一段简单的Echo Server例子: ```java 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; public class EchoServer { private final int port; public EchoServer(int port) { this.port = port; } public void start() throws Exception { EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1) EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); // (2) b.group(bossGroup, workerGroup) .channel(NioServerSocketChannel.class) // (3) .childHandler(new ChannelInitializer<SocketChannel>() { // (4) @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast(new EchoServerHandler()); } }); // Start the server. ChannelFuture f = b.bind(port).sync(); // (5) // Wait until the server socket is closed. f.channel().closeFuture().sync(); } finally { workerGroup.shutdownGracefully(); bossGroup.shutdownGracefully(); } } public static void main(String[] args) throws Exception { int port = 8080; if (args.length > 0) { port = Integer.parseInt(args[0]); } new EchoServer(port).start(); } } ``` 上述代码展示了如何设置一个基础的服务端启动过程,其中包含了两个线程组分别用来接受新的连接(`boss`) 和处理已建立好的连接 (`worker`) ,并通过管道添加处理器完成具体业务逻辑[^2]。 ---
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