Netty

Netty
- 1 Netty概览
- 2 Netty核心组件
- - 2.1 Bootstrap和ServerBootStrap（启动引导类）
  - 2.2 Channel（网络操作抽象类）
  - 2.3 EventLoop（事件循环）
  - 2.4 EventLoopGroup（事件循环组）
  - 2.7 ChannelHandler（通道处理器）
  - 2.5 ChannelHandlerContext（通道处理器上下文）
  - 2.6 ChannelPipeline（通道流水线）
  - 2.7 Bytebuf（字节缓冲区）
  - 2.8 编码器、解码器
  - 2.9 ChannelFuture（操作执行结果）
- 3 实例
- - 3.1 客户端-服务器，简单的字符串通信
  - 3.2 用Netty实现Servlet服务器
  - 3.3 用Netty实现RPC（远程过程调用）
  - 3.4 用Netty实现Websock在线聊天
  - 3.5 用Netty实现更好的在线聊天

1 Netty概览

Netty是一个客户端/服务器框架，它在Java的NIO网络组件上提供了一个简化的封装层。这使得它成为创建低级别非阻塞网络应用程序的一个不错的候选。
让我们看看Netty框架的主要亮点：
易用性：Netty比普通Java NIO更易于使用，并且有一套涵盖大多数用例的广泛示例
最小依赖性：我们将在一分钟内看到，您只需一个依赖性即可获得整个框架
性能：Netty比核心Java API具有更好的吞吐量和更低的延迟。由于其内部资源池，它还具有可扩展性。
安全性：完全支持SSL/TLS和StartTLS。

2 Netty核心组件

2.1 Bootstrap和ServerBootStrap（启动引导类）

Bootstrap 是客户端的启动引导类/辅助类，不管程序使用哪种协议，无论是创建一个客户端还是服务器都需要使用“引导”。
Bootstrap 通常使用 connet() 方法连接到远程的主机和端口，作为一个 Netty TCP 协议通信中的客户端。另外，Bootstrap 也可以通过 bind() 方法绑定本地的一个端口，作为 UDP 协议通信中的一端。具体使用方法如下：

public final class NettyClient {

    static final String HOST = "127.0.0.1";
    static final int PORT = 8007;
 
 
    public static void main(String[] args) throws Exception { 
     
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group) // Set EventLoopGroup to handle all eventsf for client.
                    .channel(NioSocketChannel.class)// Use NIO to accept new connections.
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();

                            p.addLast(new StringDecoder());
                            p.addLast(new StringEncoder());
 
                            // This is our custom client handler which will have logic for chat.
                            p.addLast(new  ClientHandler());
 
                        }
                    });
 
            // Start the client.
            ChannelFuture f = b.connect(HOST, PORT).sync();
 
             
                String input = "Frank";
                Channel channel = f.sync().channel();
                channel.writeAndFlush(input);
                channel.flush();
             
            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down the event loop to terminate all threads.
            group.shutdownGracefully();
        }
    }
}

ServerBootstrap 服务端的启动引导类/辅助类，通常使用 bind() 方法绑定本地的端口上，然后等待客户端的连接。
具体使用方法如下：

public final class NettyServer {
    // Port where chat server will listen for connections.
    static final int PORT = 8007;

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

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup) // Set boss & worker groups
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();

                            p.addLast(new StringDecoder());
                            p.addLast(new StringEncoder());

                            p.addLast(new ServerHandler());
                        }
                    });

            // Start the server.
            ChannelFuture f = b.bind(PORT).sync();
            System.out.println("Netty Server started.");

            // Wait until the server socket is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down all event loops to terminate all threads.
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

Bootstrap 只需要配置一个线程组 EventLoopGroup , 而 ServerBootstrap 需要配置两个线程组— EventLoopGroup ，一个用于接收连接，一个用于具体的 IO 处理。

2.2 Channel（网络操作抽象类）

可以简单的理解为客户端连接。
在我们使用某种语言，如 c/c++,java,go 等，进行网络编程的时候，我们通常会使用到 Socket， Socket 是对底层操作系统网络 IO 操作(如 read,write,bind,connect等)的封装，因此我们必须去学习 Socket 才能完成网络编程，而 Socket 的操作其实是比较复杂的，想要使用好它有一定难度，所以 Netty 提供了Channel(注意是 io.netty.Channel，而非 Java NIO 的 Channel)，更加方便我们处理 IO 事件。
Channel 接口是 Netty 对网络操作抽象类。通过 Channel 我们可以进行 I/O 操作。Channel 为用户提供：

当前网络连接的通道的状态（例如是否打开？是否已连接？）
网络连接的配置参数（例如接收缓冲区大小）
提供异步的网络 I/O 操作 (如建立连接，读写，绑定端口)，异步调用意味着任何 I/O调用都将立即返回，并且不保证在调用结束时所请求的 I/O 操作已完成。调用后立即返回一个 ChannelFuture 实例，通过注册监听器到ChannelFuture 上，可以在 I/O操作成功、失败或取消时回调通知调用方。
支持关联 I/O 操作与对应的处理程序

一旦客户端成功连接服务端，就会新建一个 Channel 同该用户端进行绑定。示例代码如下：

// 通过 Bootstrap 的 connect 方法连接到服务端
public Channel doConnect(InetSocketAddress inetSocketAddress) {
    CompletableFuture<Channel> completableFuture = new CompletableFuture<>();
    bootstrap.connect(inetSocketAddress).addListener((ChannelFutureListener) future -> {
        if (future.isSuccess()) {
            completableFuture.complete(future.channel());
        } else {
            throw new IllegalStateException();
        }
    });
    return completableFuture.get();
}

比较常用的Channel接口实现类是：

NioServerSocketChannel（服务端）
NioSocketChannel（客户端）

这两个 Channel 可以和 BIO 编程模型中的 ServerSocket以及Socket两个概念对应上。

2.3 EventLoop（事件循环）

事件循环可以理解为事件线程，专用于处理客户端的连接、读写事件。
Channel 为 Netty 网络操作(读写等操作)抽象类，EventLoop 负责处理注册到其上的Channel 的 I/O 操作，两者配合进行 I/O 操作。
并且，EventLoop 处理的 I/O 事件都将在它专有的 Thread 上被处理，即 Thread 和 EventLoop 属于 1 : 1 的关系，从而保证线程安全。

2.4 EventLoopGroup（事件循环组）

EventLoopGroup 包含多个 EventLoop（每一个 EventLoop 通常内部包含一个线程），它管理着所有的 EventLoop 的生命周期。
本质上是一个线程池，主要负责接收I/O请求，并分配线程执行处理请求。
ServerBootStrap可以设置两个EventLoopGroup，一个负责拿到客户端连接，一个负责每一个连接的实际的I/O。对应于多路复用的selector和IO处理线程。

2.7 ChannelHandler（通道处理器）

我们知道 Netty 是一个款基于事件驱动的网络框架，当特定事件触发时，我们能够按照自定义的逻辑去处理数据。 ChannelHandler 则正是用于处理入站（接收）和出站（发送）数据钩子，它可以处理几乎所有类型的动作，所以 ChannelHandler 会是我们开发者更为关注的一个接口。

通俗来说，ChannelHandler 是消息的具体处理器，主要负责处理客户端/服务端接收和发送的数据。

ChannelHandler 主要分为处理入站数据的 ChannelInboundHandler 和出站数据的 ChannelOutboundHandler 接口。

Netty 以适配器的形式提供了大量默认的 ChannelHandler 实现，主要目的是为了简化程序开发的过程，我们只需要重写我们关注的事件和方法就可以了。通常我们会以继承的方式使用以下适配器和抽象:

ChannelHandlerAdapter
ChannelInboundHandlerAdapter
ChannelDuplexHandler
ChannelOutboundHandlerAdapter

2.5 ChannelHandlerContext（通道处理器上下文）

用来保存ChannelHandler的上下文信息。
首先ChannelHandlerContext是一个AttributeMap，可以用来存储多个数据。
然后ChannelHandlerContext继承了ChannelInboundInvoker和ChannelOutboundInvoker,可以触发inbound和outbound的一些方法。
除了继承来的一些方法之外，ChannelHandlerContext还可以作为channel，handler和pipline的沟通桥梁，因为可以从ChannelHandlerContext中获取到对应的channel，handler和pipline：

Channel channel();
ChannelHandler handler();
ChannelPipeline pipeline();

还要注意的是ChannelHandlerContext还返回一个EventExecutor，用来执行特定的任务：

2.6 ChannelPipeline（通道流水线）

当 Channel 被创建时，它会被自动地分配到它专属的 ChannelPipeline。一个 Channel 包含一个 ChannelPipeline。 ChannelPipeline 为 ChannelHandler 的链，一个 pipeline 上可以有多个 ChannelHandler。

我们可以在 ChannelPipeline 上通过 addLast() 方法添加一个或者多个ChannelHandler （一个数据或者事件可能会被多个 Handler 处理）。当一个 ChannelHandler 处理完之后就将数据交给下一个 ChannelHandler ：

	b.group(eventLoopGroup)
    .handler(new ChannelInitializer<SocketChannel>() {
        @Override
        protected void initChannel(SocketChannel ch) {
            ch.pipeline().addLast(new NettyKryoDecoder(kryoSerializer, RpcResponse.class));
            ch.pipeline().addLast(new NettyKryoEncoder(kryoSerializer, RpcRequest.class));
            ch.pipeline().addLast(new KryoClientHandler());
        }
    });

入站事件和出站事件的流向
从服务端角度来看，如果一个事件的运动方向是从客户端到服务端，那么这个事件是入站的，如果事件运动的方向是从服务端到客户端，那么这个事件是出站的。

上图是 Netty 事件入站和出站的大致流向，入站和出站的 ChannelHandler 可以被安装到一个ChannelPipeline中，如果一个消息或其他的入站事件被[读取]，那么它会从ChannelPipeline的头部开始流动，并传递给第一个ChannelInboundHandler ，这个ChannelHandler的行为取决于它的具体功能，不一定会修改消息。在经历过第一个ChannelInboundHandler之后，消息会被传递给这条ChannelHandler链的下一个ChannelHandler，最终消息会到达ChannelPipeline尾端，消息的读取也就结束了。

数据的出站 (发送) 流程与入站是相似的，在出站过程中，消息从ChannelOutboundHandler链的尾端开始流动，直到到达它的头部为止，在这之后，消息会到达网络传输层进行后续传输。

鉴于入站操作和出站操作是不同的，可能有同学会疑惑：为什么入站 ChannelHandler和出站 ChannelHandler的数据不会窜流呢(为什么入站的数据不会到出站 ChannelHandler 链中)？

因为Netty可以区分ChannelInboundHandler和 ChannelOutboundHandler的实现，并确保数据只在两个相同类型的ChannelHandler直接传递，即数据要么在 ChannelInboundHandler链之间流动，要么在ChannelOutboundHandler链之间流动。

当ChannelHandler被添加到ChannelPipeline中后，它会被分配一个ChannelHandlerContext，它代表了ChannelHandler和ChannelPipeline之间的绑定。 ChannelPipeline 通过 ChannelHandlerContext来间接管理 ChannelHandler 。

2.7 Bytebuf（字节缓冲区）

网络通信最终都是通过字节流进行传输的。 Netty 使用自建的 buffer API，而不是使用 NIO 的 ByteBuffer 来存储连续的字节序列。与 ByteBuffer 相比这种方式拥有明显的优势。Netty 使用新的 buffer 类型 ByteBuf，被设计为一个可从底层解决 ByteBuffer 问题，并可满足日常网络应用开发需要的缓冲类型。这些很酷的特性包括：

如果需要，允许使用自定义的缓冲类型。
复合缓冲类型中内置的透明的零拷贝实现。
开箱即用的动态缓冲类型，具有像 StringBuffer 一样的动态缓冲能力。
不再需要调用的 flip() 方法。
正常情况下具有比 ByteBuffer 更快的响应速度。

2.8 编码器、解码器

当我们通过 Netty 发送(出站)或接收(入站)一个消息时，就会发生一次数据的转换，因为数据在网络中总是通过字节传输的，所以当数据入站时，Netty 会解码数据，即把数据从字节转为为另一种格式 (通常是一个 Java 对象)，当数据出站时，Netty 会编码数据，即把数据从它当前格式转为为字节。

Netty 为编码器和解码器提供了不同类型的抽象，这些编码器和解码器其实都是ChannelHandler的实现，它们的名称通常是 ByteToMessageDecoder 和 MessageToByteEncoder。

对于入站数据来说，解码其实是解码器通过重写 ChannelHanler 的read事件（channelRead），然后调用它们自己的 decode方法完成的。对于出站数据来说，编码则是编码器通过重写ChannelHanler的write事件，然后调用它们自己的 encode方法完成的。

2.9 ChannelFuture（操作执行结果）

public interface ChannelFuture extends Future<Void> {
    Channel channel();

    ChannelFuture addListener(GenericFutureListener<? extends Future<? super Void>> var1);
     ......

    ChannelFuture sync() throws InterruptedException;
}

Netty 是非阻塞的，因此，我们不能立刻得到操作是否执行成功，但是，你可以通过 ChannelFuture 接口的 addListener() 方法注册一个监听 ChannelFutureListener，当操作执行成功或者失败时，监听就会自动触发返回结果。

ChannelFuture f = b.connect(host, port).addListener(future -> {
  if (future.isSuccess()) {
    System.out.println("连接成功!");
  } else {
    System.err.println("连接失败!");
  }
}).sync();

并且，你还可以通过ChannelFuture 的 channel() 方法获取连接相关联的Channel 。

Channel channel = f.channel();

另外，我们还可以通过 ChannelFuture 接口的 sync()方法让异步的操作编程同步的。

// bind()是异步的，但是，你可以通过 `sync()`方法将其变为同步。
ChannelFuture f = b.bind(port).sync();

3 实例

3.1 客户端-服务器，简单的字符串通信

这个例子实现了简单的通信，客户端发送字符串到服务端，服务端收到后返回一个字符串。
服务端：

package com.qupeng.java.demo.netty4.official.demo;

import java.util.ArrayList;
import java.util.List;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public final class NettyServer {
    // Port where chat server will listen for connections.
    static final int PORT = 8007;

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

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup) // Set boss & worker groups
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();

                            p.addLast(new StringDecoder());
                            p.addLast(new StringEncoder());

                            p.addLast(new ServerHandler());
                        }
                    });

            // Start the server.
            ChannelFuture f = b.bind(PORT).sync();
            System.out.println("Netty Server started.");

            // Wait until the server socket is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down all event loops to terminate all threads.
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

@Sharable
class ServerHandler extends SimpleChannelInboundHandler<String> {

    static final List<Channel> channels = new ArrayList<Channel>();

    @Override
    public void channelActive(final ChannelHandlerContext ctx) {
        System.out.println("Client joined - " + ctx);
        channels.add(ctx.channel());
    }

    @Override
    public void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println("Message received: " + msg);
        for (Channel c : channels) {
            c.writeAndFlush("Hello " + msg + '\n');
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        System.out.println("Closing connection for client - " + ctx);
        ctx.close();
    }
}

客户端：

package com.qupeng.java.demo.netty4.official.demo;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;


 
public final class NettyClient {

    static final String HOST = "127.0.0.1";
    static final int PORT = 8007;
 
 
    public static void main(String[] args) throws Exception { 
     
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group) // Set EventLoopGroup to handle all eventsf for client.
                    .channel(NioSocketChannel.class)// Use NIO to accept new connections.
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();

                            p.addLast(new StringDecoder());
                            p.addLast(new StringEncoder());
 
                            // This is our custom client handler which will have logic for chat.
                            p.addLast(new  ClientHandler());
 
                        }
                    });
 
            // Start the client.
            ChannelFuture f = b.connect(HOST, PORT).sync();
 
             
                String input = "Frank";
                Channel channel = f.sync().channel();
                channel.writeAndFlush(input);
                channel.flush();
             
            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down the event loop to terminate all threads.
            group.shutdownGracefully();
        }
    }
}
  class  ClientHandler extends SimpleChannelInboundHandler<String> {  
 
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
            System.out.println("Message from Server: " + msg);
     
        }
     
    }

参考链接: http://www.mastertheboss.com/jboss-frameworks/netty/jboss-netty-tutorial

3.2 用Netty实现Servlet服务器

这个例子实现了一个简单的Tomcat服务器，支持了一个/hello-world的servlet mappin.
服务端：

package com.qupeng.java.demo.netty4.servlet;

import com.qupeng.java.demo.netty4.servlet.handler.TomcatHandler;
import com.qupeng.java.demo.netty4.servlet.service.MyServlet;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

import java.io.FileInputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.stream.Collectors;


//Netty就是一个同时支持多协议的网络通信框架
public class MyTomcatServer {
	//打开Tomcat源码，全局搜索ServerSocket

	private int port = 8080;

	private Map<String, MyServlet> servletMapping = new HashMap<>();

	private Properties webxml = new Properties();

	private TomcatHandler tomcatHandler;

	private void init(){

		try{
			String WEB_INF = this.getClass().getResource("/").getPath();
			FileInputStream fis = new FileInputStream(WEB_INF + "web.xml");
			SAXReader saxReader = new SAXReader();
			Document document = saxReader.read(fis);
			Element root = document.getRootElement();

			List<Element> servlets = root.elements("servlet");
			Map<String, String> servletClassMap = servlets.stream().collect(Collectors.toMap(element -> element.element("servlet-name").getText(), element -> element.element("servlet-class").getText()));

			List<Element> servletMappings = root.elements("servlet-mapping");
			servletMapping = servletMappings.stream().collect(Collectors.toMap(element -> element.element("url-pattern").getText(), element -> {
				String classPath = servletClassMap.get(element.element("servlet-name").getText());
				MyServlet obj = null;
				try {
					obj = (MyServlet)Class.forName(classPath).newInstance();
				} catch (InstantiationException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (ClassNotFoundException e) {
					e.printStackTrace();
				}
				return obj;
			}));
			tomcatHandler = new TomcatHandler(servletMapping);
		}catch(Exception e){
			e.printStackTrace();
		}
	}

	public void start(){

		init();
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap server = new ServerBootstrap();

			server.group(bossGroup, workerGroup)
					// 主线程处理类,看到这样的写法，底层就是用反射
					.channel(NioServerSocketChannel.class)
					// 子线程处理类 , Handler
					.childHandler(new ChannelInitializer<SocketChannel>() {
						// 客户端初始化处理
						protected void initChannel(SocketChannel client) throws Exception {
							// 无锁化串行编程
							//Netty对HTTP协议的封装，顺序有要求
							// HttpResponseEncoder 编码器
							// 责任链模式，双向链表Inbound OutBound
							client.pipeline().addLast(new HttpResponseEncoder());
							// HttpRequestDecoder 解码器
							client.pipeline().addLast(new HttpRequestDecoder());
							// 业务逻辑处理
							client.pipeline().addLast(new TomcatHandler(servletMapping));
						}
					})
					// 针对主线程的配置 分配线程最大数量 128
					.option(ChannelOption.SO_BACKLOG, 128)
					// 针对子线程的配置 保持长连接
					.childOption(ChannelOption.SO_KEEPALIVE, true);

			//3、启动服务器
			ChannelFuture f = server.bind(port).sync();
			System.out.println("My Tomcat 已启动，监听的端口是：" + port);
			f.channel().closeFuture().sync();
		}catch (Exception e){
			e.printStackTrace();
		}finally {
			// 关闭线程池
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) {
		new MyTomcatServer().start();
	}

}

package com.qupeng.java.demo.netty4.servlet.handler;

import com.qupeng.java.demo.netty4.servlet.service.MyServlet;
import com.qupeng.java.demo.netty4.servlet.http.HttpServletRequest;
import com.qupeng.java.demo.netty4.servlet.http.HttpServletResponse;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.HttpRequest;

import java.util.Map;

public class TomcatHandler extends ChannelInboundHandlerAdapter {

	private Map<String, MyServlet> servletMapping;

	public TomcatHandler(Map<String, MyServlet> servletMapping) {
		this.servletMapping = servletMapping;
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		if (msg instanceof HttpRequest){
			HttpRequest req = (HttpRequest) msg;
			String uri = req.uri();

			HttpServletRequest servletRequest = new HttpServletRequest(req);
			HttpServletResponse servletResponse = new HttpServletResponse(ctx);
			if(servletMapping.containsKey(uri)){
				servletMapping.get(uri).service(servletRequest, servletResponse);
			}else{
				servletResponse.setStatus(404);
				servletResponse.setContentType("text/html");
				servletResponse.getPrintWriter().write("404 - Not Found");
			}

		}
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {

	}
}

Servlet API:

package com.qupeng.java.demo.netty4.servlet.service;

import com.qupeng.java.demo.netty4.servlet.http.HttpServletRequest;
import com.qupeng.java.demo.netty4.servlet.http.HttpServletResponse;

public abstract class MyServlet {
	
	public void service(HttpServletRequest request, HttpServletResponse response) throws Exception{
		if("GET".equalsIgnoreCase(request.getMethod())){
			doGet(request, response);
		}else{
			doPost(request, response);
		}
	}
	
	public abstract void doGet(HttpServletRequest request, HttpServletResponse response) throws Exception;
	
	public abstract void doPost(HttpServletRequest request, HttpServletResponse response) throws Exception;
	
}

package com.qupeng.java.demo.netty4.servlet.service;

import com.qupeng.java.demo.netty4.servlet.http.HttpServletRequest;
import com.qupeng.java.demo.netty4.servlet.http.HttpServletResponse;

public class HelloWorldServlet extends MyServlet {
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws Exception {
        this.doPost(request, response);
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws Exception {
        response.getPrintWriter().write("Hello world!");
    }
}

package com.qupeng.java.demo.netty4.servlet.http;

import io.netty.handler.codec.http.HttpRequest;

public class HttpServletRequest {
    private HttpRequest req;

    public HttpServletRequest(HttpRequest req) {
        this.req = req;
    }

    public String getUrl() {
        return req.uri();
    }

    public String getMethod() {
        return req.method().name();
    }
}

package com.qupeng.java.demo.netty4.servlet.http;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;

public class HttpServletResponse {
    private PrintWriter printWriter;

    private FullHttpResponse httpResponse;

    public HttpServletResponse(ChannelHandlerContext ctx) {
        this.printWriter = new PrintWriter(ctx, this);
        httpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
    }

    public PrintWriter getPrintWriter() {
        return printWriter;
    }

    public void setStatus(int sc) {
        httpResponse.setStatus(HttpResponseStatus.valueOf(sc));
    }

    public void setHeader(String name,String value) {
        httpResponse.headers().set(name, value);
    }

    public void setContentType(String type) {
        httpResponse.headers().set("Content-Type", type);
    }

    public FullHttpResponse getHttpResponse() {
        return httpResponse;
    }
}

package com.qupeng.java.demo.netty4.servlet.http;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;

public class PrintWriter {

    private ChannelHandlerContext ctx;

    private HttpServletResponse servletResponse;

    public PrintWriter(ChannelHandlerContext ctx, HttpServletResponse servletResponse) {
        this.ctx = ctx;
        this.servletResponse = servletResponse;
    }

    public void write(String str) { ;
        servletResponse.setContentType("text/html");
        ctx.write(servletResponse.getHttpResponse().replace(Unpooled.wrappedBuffer(str.getBytes())));
        ctx.flush();
        ctx.close();
    }
}

web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="true">
    <servlet>
        <servlet-name>hello-world</servlet-name>
        <servlet-class>com.qupeng.java.demo.netty4.servlet.service.HelloWorldServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>hello-world</servlet-name>
        <url-pattern>/hello-world</url-pattern>
    </servlet-mapping>
</web-app>

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.qupeng.java.demos</groupId>
    <artifactId>netty4</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.52.Final</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.25</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

        <dependency>
            <groupId>org.dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>2.0.0</version>
        </dependency>
    </dependencies>
</project>

3.3 用Netty实现RPC（远程过程调用）

这个例子来自《Netty4核心原理与手写RCP框架实战》一书，实现了客户端远程调用服务端的数值计算功能。
服务端：

package com.qupeng.java.demo.netty4.rpc.registry;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;

public class RpcRegistry {  
    private int port;  
    public RpcRegistry(int port){  
        this.port = port;  
    }  
    public void start(){  
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
          
        try {  
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
            		.channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
  
                        @Override  
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            //自定义协议解码器
                            /** 入参有5个，分别解释如下
                             maxFrameLength：框架的最大长度。如果帧的长度大于此值，则将抛出TooLongFrameException。
                             lengthFieldOffset：长度字段的偏移量：即对应的长度字段在整个消息数据中得位置
                             lengthFieldLength：长度字段的长度。如：长度字段是int型表示，那么这个值就是4（long型就是8）
                             lengthAdjustment：要添加到长度字段值的补偿值
                             initialBytesToStrip：从解码帧中去除的第一个字节数
                             */
                            pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
                            //自定义协议编码器
                            pipeline.addLast(new LengthFieldPrepender(4));
                            //对象参数类型编码器
                            pipeline.addLast("encoder",new ObjectEncoder());
                            //对象参数类型解码器
                            pipeline.addLast("decoder",new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.cacheDisabled(null)));
                            pipeline.addLast(new RegistryHandler());
                        }  
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture future = b.bind(port).sync();
            System.out.println("GP RPC Registry start listen at " + port );
            future.channel().closeFuture().sync();    
        } catch (Exception e) {  
             bossGroup.shutdownGracefully();    
             workerGroup.shutdownGracefully();  
        }  
    }
    
    
    public static void main(String[] args) throws Exception {    
        new RpcRegistry(8080).start();    
    }    
}

package com.qupeng.java.demo.netty4.rpc.registry;

import com.qupeng.java.demo.netty4.rpc.protocol.InvokerProtocol;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.io.File;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;

public class RegistryHandler  extends ChannelInboundHandlerAdapter {

	//用保存所有可用的服务
    public static ConcurrentHashMap<String, Object> registryMap = new ConcurrentHashMap<String,Object>();

    //保存所有相关的服务类
    private List<String> classNames = new ArrayList<String>();
    
    public RegistryHandler(){
    	//完成递归扫描
    	scannerClass("com.qupeng.java.demo.netty4.rpc.provider");
    	doRegister();
    }
    
    
    @Override    
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    	Object result = new Object();
        InvokerProtocol request = (InvokerProtocol)msg;

        //当客户端建立连接时，需要从自定义协议中获取信息，拿到具体的服务和实参
		//使用反射调用
        if(registryMap.containsKey(request.getClassName())){ 
        	Object clazz = registryMap.get(request.getClassName());
        	Method method = clazz.getClass().getMethod(request.getMethodName(), request.getParames());    
        	result = method.invoke(clazz, request.getValues());   
        }
        ctx.write(result);  
        ctx.flush();    
        ctx.close();  
    }
    
    @Override    
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         cause.printStackTrace();    
         ctx.close();    
    }
    

    /*
     * 递归扫描
     */
	private void scannerClass(String packageName){
		URL url = this.getClass().getClassLoader().getResource(packageName.replaceAll("\\.", "/"));
		File dir = new File(url.getFile());
		for (File file : dir.listFiles()) {
			//如果是一个文件夹，继续递归
			if(file.isDirectory()){
				scannerClass(packageName + "." + file.getName());
			}else{
				classNames.add(packageName + "." + file.getName().replace(".class", "").trim());
			}
		}
	}

	/**
	 * 完成注册
	 */
	private void doRegister(){
		if(classNames.size() == 0){ return; }
		for (String className : classNames) {
			try {
				Class<?> clazz = Class.forName(className);
				Class<?> i = clazz.getInterfaces()[0];
				registryMap.put(i.getName(), clazz.newInstance());
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
  
}

package com.qupeng.java.demo.netty4.rpc.protocol;

import lombok.Data;

import java.io.Serializable;

/**
 * 自定义传输协议
 */
@Data
public class InvokerProtocol implements Serializable {

    private String className;//类名
    private String methodName;//函数名称 
    private Class<?>[] parames;//形参列表
    private Object[] values;//实参列表

}

远程服务接口定义：

package com.qupeng.java.demo.netty4.rpc.api;

public interface IRpcHelloService {
    String hello(String name);  
}

package com.qupeng.java.demo.netty4.rpc.api;

public interface IRpcService {

	/** 加 */
	public int add(int a, int b);

	/** 减 */
	public int sub(int a, int b);

	/** 乘 */
	public int mult(int a, int b);

	/** 除 */
	public int div(int a, int b);

}

package com.qupeng.java.demo.netty4.rpc.provider;

import com.qupeng.java.demo.netty4.rpc.api.IRpcHelloService;

public class RpcHelloServiceImpl implements IRpcHelloService {

    public String hello(String name) {  
        return "Hello " + name + "!";  
    }  
  
}

package com.qupeng.java.demo.netty4.rpc.provider;

import com.qupeng.java.demo.netty4.rpc.api.IRpcService;

public class RpcServiceImpl implements IRpcService {

	public int add(int a, int b) {
		return a + b;
	}

	public int sub(int a, int b) {
		return a - b;
	}

	public int mult(int a, int b) {
		return a * b;
	}

	public int div(int a, int b) {
		return a / b;
	}

}

客户端实现：

package com.qupeng.java.demo.netty4.rpc.consumer.proxy;

import com.qupeng.java.demo.netty4.rpc.protocol.InvokerProtocol;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class RpcProxy {  
	
	public static <T> T create(Class<?> clazz){
        //clazz传进来本身就是interface
        MethodProxy proxy = new MethodProxy(clazz);
        Class<?> [] interfaces = clazz.isInterface() ?
                                new Class[]{clazz} :
                                clazz.getInterfaces();
        T result = (T) Proxy.newProxyInstance(clazz.getClassLoader(),interfaces,proxy);
        return result;
    }

	private static class MethodProxy implements InvocationHandler {
		private Class<?> clazz;
		public MethodProxy(Class<?> clazz){
			this.clazz = clazz;
		}

		public Object invoke(Object proxy, Method method, Object[] args)  throws Throwable {
			//如果传进来是一个已实现的具体类（本次演示略过此逻辑)
			if (Object.class.equals(method.getDeclaringClass())) {
				try {
					return method.invoke(this, args);
				} catch (Throwable t) {
					t.printStackTrace();
				}
				//如果传进来的是一个接口（核心)
			} else {
				return rpcInvoke(proxy,method, args);
			}
			return null;
		}


		/**
		 * 实现接口的核心方法
		 * @param method
		 * @param args
		 * @return
		 */
		public Object rpcInvoke(Object proxy,Method method,Object[] args){

			//传输协议封装
			InvokerProtocol msg = new InvokerProtocol();
			msg.setClassName(this.clazz.getName());
			msg.setMethodName(method.getName());
			msg.setValues(args);
			msg.setParames(method.getParameterTypes());

			final RpcProxyHandler consumerHandler = new RpcProxyHandler();
			EventLoopGroup group = new NioEventLoopGroup();
			try {
				Bootstrap b = new Bootstrap();
				b.group(group)
						.channel(NioSocketChannel.class)
						.option(ChannelOption.TCP_NODELAY, true)
						.handler(new ChannelInitializer<SocketChannel>() {
							@Override
							public void initChannel(SocketChannel ch) throws Exception {
								ChannelPipeline pipeline = ch.pipeline();
								//自定义协议解码器
								/** 入参有5个，分别解释如下
								 maxFrameLength：框架的最大长度。如果帧的长度大于此值，则将抛出TooLongFrameException。
								 lengthFieldOffset：长度字段的偏移量：即对应的长度字段在整个消息数据中得位置
								 lengthFieldLength：长度字段的长度：如：长度字段是int型表示，那么这个值就是4（long型就是8）
								 lengthAdjustment：要添加到长度字段值的补偿值
								 initialBytesToStrip：从解码帧中去除的第一个字节数
								 */
								pipeline.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
								//自定义协议编码器
								pipeline.addLast("frameEncoder", new LengthFieldPrepender(4));
								//对象参数类型编码器
								pipeline.addLast("encoder", new ObjectEncoder());
								//对象参数类型解码器
								pipeline.addLast("decoder", new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.cacheDisabled(null)));
								pipeline.addLast("handler",consumerHandler);
							}
						});

				ChannelFuture future = b.connect("localhost", 8080).sync();
				future.channel().writeAndFlush(msg).sync();
				future.channel().closeFuture().sync();
			} catch(Exception e){
				e.printStackTrace();
			}finally {
				group.shutdownGracefully();
			}
			return consumerHandler.getResponse();
		}

	}
}

package com.qupeng.java.demo.netty4.rpc.consumer.proxy;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class
RpcProxyHandler extends ChannelInboundHandlerAdapter {
	  
    private Object response;    
      
    public Object getResponse() {    
	    return response;    
	}    
  
    @Override    
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        response = msg;
    }    
        
    @Override    
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("client exception is general");    
    }    
}

package com.qupeng.java.demo.netty4.rpc.consumer;


import com.qupeng.java.demo.netty4.rpc.api.IRpcHelloService;
import com.qupeng.java.demo.netty4.rpc.api.IRpcService;
import com.qupeng.java.demo.netty4.rpc.consumer.proxy.RpcProxy;

public class RpcConsumer {
	
    public static void main(String [] args){  
        IRpcHelloService rpcHello = RpcProxy.create(IRpcHelloService.class);
        
        System.out.println(rpcHello.hello("world"));

        IRpcService service = RpcProxy.create(IRpcService.class);
        
        System.out.println("8 + 2 = " + service.add(8, 2));
        System.out.println("8 - 2 = " + service.sub(8, 2));
        System.out.println("8 * 2 = " + service.mult(8, 2));
        System.out.println("8 / 2 = " + service.div(8, 2));
    }
    
}

3.4 用Netty实现Websock在线聊天

这个例子实现了一个简单的在线聊天，浏览器与服务端建立websocket链接，可以发送文本消息到服务端，服务端推送消息到所有的客户端。
在这里插入图片描述
页面：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Netty WebSocket Chat Room</title>
    <style type="text/css">
        .border{
            border: 1px solid #73AD21;
        }
        .container{
            height: 700px;
            display: flex;
            flex-direction: column;
            align-items:center;
        }
        .banner{
            background:#73AD21;
            height: 28px;
            width: 402px;
            font-size:12px;
        }
        .online-msg{
            background:#EFEFF4;
            font-size:12px;
            color:#666;
            height: 300px;
            width: 380px;
		    padding: 10px;
        }
        .tool-box{
             background-color:#e7eff8;
             height:35px;
             width: 402px;
        }
        .input-text{
            font-size:12px;
            color:#666;
            height: 150px;
            width: 380px;
    		padding: 10px;
        }
        .input-action{
            display: flex;
            justify-content:flex-end;
        }
    </style>
</head>
<br>
<body>
<br>
<script type="text/javascript">
    var socket;
    if (!window.WebSocket) {
        window.WebSocket = window.MozWebSocket;
    }
    if (window.WebSocket) {
        socket = new WebSocket("ws://localhost:8080/websocket");
        socket.onmessage = function (event) {
            var ta = document.getElementById('online-msg');
            ta.append(document.createElement('br'));
            ta.append(event.data);
        };
        socket.onopen = function (event) {
            var ta = document.getElementById('online-msg');
            ta.append("打开WebSocket服务正常，浏览器支持WebSocket!");
        };
        socket.onclose = function (event) {
            var ta = document.getElementById('responseText');
            ta.append("WebSocket 关闭!");
        };
    }
    else {
        alert("抱歉，您的浏览器不支持WebSocket协议!");
    }

    function send() {
        if (!window.WebSocket) {
            return;
        }
        if (socket.readyState == WebSocket.OPEN) {
            var ta = document.getElementById('send-message');
            socket.send(ta.innerText);
            ta.innerText = '';
        }
        else {
            alert("WebSocket连接没有建立成功!");
        }
    }
</script>
<div class="container">
    <div class="banner">
        <div style="line-height: 28px;color:#fff;">
            <span style="text-align:left;margin-left:10px;">Netty Websocket聊天室</span>
        </div>
    </div>
    <div class="online-msg border" id="online-msg">
    </div>
    <form onsubmit="return false;">
        <div class="tool-box">
        </div>
        <div class="input-text border" contenteditable="true" id="send-message">
        </div>
        <div class="input-action">
            <input class="button" type="button" id="mjr_send" onclick="send()" value="发送"/>
        </div>
    </form>
</div>
</body>
</html>

服务端：

package com.qupeng.java.demo.netty4.websocket.simple.chat;

import com.qupeng.java.demo.netty4.websocket.simple.chat.handler.HttpServerHandler;
import com.qupeng.java.demo.netty4.websocket.simple.chat.handler.WebSocketServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.stream.ChunkedWriteHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class SimpleWebSocketChatServer {
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args.length > 0) {
            try {
                port = Integer.parseInt(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        new SimpleWebSocketChatServer().run(port);
    }

    public void run(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {

                        @Override
                        protected void initChannel(SocketChannel ch)
                                throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast("http-codec", new HttpServerCodec());
                            pipeline.addLast("aggregator", new HttpObjectAggregator(65536));
                            pipeline.addLast("http-chunked", new ChunkedWriteHandler());
                            pipeline.addLast("http-server-handler", new HttpServerHandler());
                            pipeline.addLast("websocket-server-handler", new WebSocketServerHandler());
                        }
                    });

            Channel ch = b.bind(port).sync().channel();
            System.out.println("Web socket server started at port " + port
                    + '.');
            System.out.println("Open your browser and navigate to http://localhost:"+ port + '/');
            ch.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

package com.qupeng.java.demo.netty4.websocket.simple.chat.handler;

import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;
import lombok.extern.slf4j.Slf4j;

import java.io.File;
import java.io.RandomAccessFile;
import java.net.URL;


@Slf4j
public class HttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private final String webroot = "webroot";
    
    //获取class路径
    private URL baseURL = HttpServerHandler.class.getResource("");

    private WebSocketServerHandshaker handshaker;

    @Override
    public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        if (handleWebsocketConnectionRequest(ctx, request)) {
            return;
        }

        String uri = request.uri();

        RandomAccessFile file = null;
        try {
            String page = uri.equals("/") ? "simple-chat.html" : uri;
            file = new RandomAccessFile(getResource(page), "r");
        } catch (Exception e) {
            ctx.fireChannelRead(request.retain());
            return;
        }

        HttpResponse response = new DefaultHttpResponse(request.protocolVersion(), HttpResponseStatus.OK);
        String contextType = "text/html;";
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, contextType + "charset=utf-8;");

        boolean keepAlive = HttpUtil.isKeepAlive(request);

        if (keepAlive) {
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, file.length());
            response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
        }
        ctx.write(response);

        ctx.write(new DefaultFileRegion(file.getChannel(), 0, file.length()));

        ChannelFuture future = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        if (!keepAlive) {
            future.addListener(ChannelFutureListener.CLOSE);
        }

        file.close();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        Channel client = ctx.channel();
        log.info("Client:" + client.remoteAddress() + "异常");
        // 当出现异常就关闭连接
        cause.printStackTrace();
        ctx.close();
    }

    private boolean handleWebsocketConnectionRequest(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception {

        // 如果HTTP解码失败，返回HHTP异常
        if (!req.decoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
            return false;
        }

        // 构造握手响应返回，本机测试
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
                "ws://localhost:8080/websocket", null, false);
        handshaker = wsFactory.newHandshaker(req);
        if (handshaker == null) {
            WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
        } else {
            handshaker.handshake(ctx.channel(), req);
        }

        return true;
    }

    private File getResource(String fileName) throws Exception {
        String basePath = baseURL.toURI().toString();
        int start = basePath.indexOf("classes/");
        basePath = (basePath.substring(0, start) + "/" + "classes/").replaceAll("/+", "/");

        String path = basePath + webroot + "/" + fileName;
        log.info("BaseURL:" + basePath);
        path = !path.contains("file:") ? path : path.substring(5);
        path = path.replaceAll("//", "/");
        return new File(path);
    }
}

package com.qupeng.java.demo.netty4.websocket.simple.chat.handler;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.ChannelGroupException;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.util.concurrent.GlobalEventExecutor;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class WebSocketServerHandler extends SimpleChannelInboundHandler<WebSocketFrame> {

    private static ChannelGroup onlineUsers = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    private WebSocketServerHandshaker handshaker;

    @Override
    public void channelRead0(ChannelHandlerContext ctx, WebSocketFrame msg) throws Exception {
        handleWebSocketFrame(ctx, msg);
    }

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

    private void handleWebSocketFrame(ChannelHandlerContext ctx,
                                      WebSocketFrame frame) {

        // 判断是否是关闭链路的指令
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(),
                    (CloseWebSocketFrame) frame.retain());
            return;
        }
        // 判断是否是Ping消息
        if (frame instanceof PingWebSocketFrame) {
            ctx.channel().write(
                    new PongWebSocketFrame(frame.content().retain()));
            return;
        }
        // 本例程仅支持文本消息，不支持二进制消息
        if (!(frame instanceof TextWebSocketFrame)) {
            throw new UnsupportedOperationException(String.format(
                    "%s frame types not supported", frame.getClass().getName()));
        }

        onlineUsers.add(ctx.channel());

        try {
            String request = ((TextWebSocketFrame) frame).text();
            onlineUsers.writeAndFlush(new TextWebSocketFrame(new java.util.Date().toString() + " " + request));
        } catch (ChannelGroupException ex) {
            log.error("推送组播消息失败。", ex);
        }
    }

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

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.qupeng.java.demos</groupId>
    <artifactId>netty4</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.52.Final</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.25</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>

</project>

3.5 用Netty实现更好的在线聊天

这个例子改编自《Netty4核心原理与手写RCP框架实战》一书，实现了一个完整的在线聊天功能，除了浏览器聊天，还支持在控制台推送系统消息给所有浏览器啊，我在原有基础上添加了退出聊天室的功能。
在这里插入图片描述

服务端：

package com.qupeng.java.demo.netty4.websocket.chat.server;

import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMDecoder;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMEncoder;
import com.qupeng.java.demo.netty4.websocket.chat.server.handler.HttpServerHandler;
import com.qupeng.java.demo.netty4.websocket.chat.server.handler.TerminalServerHandler;
import com.qupeng.java.demo.netty4.websocket.chat.server.handler.WebSocketServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class WebSocketChatServer {
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args.length > 0) {
            try {
                port = Integer.parseInt(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        new WebSocketChatServer().run(port);
    }

    public void run(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {

                        @Override
                        protected void initChannel(SocketChannel ch)
                                throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            /** 解析自定义协议 */
                            pipeline.addLast(new IMDecoder());  //Inbound
                            pipeline.addLast(new IMEncoder());  //Outbound
                            pipeline.addLast(new TerminalServerHandler());  //Inbound
                            pipeline.addLast("http-codec", new HttpServerCodec());
                            pipeline.addLast("aggregator", new HttpObjectAggregator(65536));
                            pipeline.addLast("http-chunked", new ChunkedWriteHandler());
                            pipeline.addLast("http-server-handler", new HttpServerHandler());
                            pipeline.addLast(new WebSocketServerProtocolHandler("/im"));
                            pipeline.addLast("websocket-server-handler", new WebSocketServerHandler());
                        }
                    });

            Channel ch = b.bind(port).sync().channel();
            System.out.println("Web socket server started at port " + port
                    + '.');
            System.out.println("Open your browser and navigate to http://localhost:"+ port + '/');
            ch.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

package com.qupeng.java.demo.netty4.websocket.chat.server.handler;

import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMMessage;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class TerminalServerHandler extends SimpleChannelInboundHandler<IMMessage> {

	private MsgProcessor processor = new MsgProcessor();
	
	@Override
	protected void channelRead0(ChannelHandlerContext ctx, IMMessage msg) throws Exception {
	    processor.sendMsg(ctx.channel(), msg);
    }

    /**
     * 异常处理
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        log.info("Socket Client: 与客户端断开连接:" + cause.getMessage());
        cause.printStackTrace();
        ctx.close();
    }

}

package com.qupeng.java.demo.netty4.websocket.chat.server.handler;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import lombok.extern.slf4j.Slf4j;

import java.io.File;
import java.io.RandomAccessFile;
import java.net.URL;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


@Slf4j
public class HttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private final String webroot = "webroot";
    
    //获取class路径
    private URL baseURL = HttpServerHandler.class.getResource("");

    private MsgProcessor processor = new MsgProcessor();

    @Override
    public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        String uri = request.uri();
        if (uri.startsWith("/logout")) {
            String nickName = getGetParamsFromChannel(request).get("nickname").toString();
            processor.logout(ctx.channel(), nickName);
            String data = "logout";
            ByteBuf buf = Unpooled.wrappedBuffer(data.getBytes());
            FullHttpResponse response = new DefaultFullHttpResponse(request.protocolVersion(), HttpResponseStatus.OK, buf);
            if(buf != null){
                response.headers().set("Content-Type","text/plain;charset=UTF-8");
                response.headers().set("Content-Length",response.content().readableBytes());
            }
            ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
            return;
        }

        RandomAccessFile file = null;
        try {
            String page = uri.equals("/") ? "chat.html" : uri;
            file = new RandomAccessFile(getResource(page), "r");
        } catch (Exception e) {
            ctx.fireChannelRead(request.retain());
            return;
        }

        HttpResponse response = new DefaultHttpResponse(request.protocolVersion(), HttpResponseStatus.OK);
        String contextType = "text/html;";
        if (uri.endsWith(".css")) {
            contextType = "text/css;";
        } else if (uri.endsWith(".js")) {
            contextType = "text/javascript;";
        } else if (uri.toLowerCase().matches(".*\\.(jpg|png|gif)$")) {
            String ext = uri.substring(uri.lastIndexOf("."));
            contextType = "image/" + ext;
        }
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, contextType + "charset=utf-8;");

        boolean keepAlive = HttpUtil.isKeepAlive(request);

        if (keepAlive) {
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, file.length());
            response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
        }
        ctx.write(response);

        ctx.write(new DefaultFileRegion(file.getChannel(), 0, file.length()));

        ChannelFuture future = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        if (!keepAlive) {
            future.addListener(ChannelFutureListener.CLOSE);
        }

        file.close();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        Channel client = ctx.channel();
        log.info("Client:" + client.remoteAddress() + "异常");
        // 当出现异常就关闭连接
        cause.printStackTrace();
        ctx.close();
    }

    private File getResource(String fileName) throws Exception {
        String basePath = baseURL.toURI().toString();
        int start = basePath.indexOf("classes/");
        basePath = (basePath.substring(0, start) + "/" + "classes/").replaceAll("/+", "/");

        String path = basePath + webroot + "/" + fileName;
        log.info("BaseURL:" + basePath);
        path = !path.contains("file:") ? path : path.substring(5);
        path = path.replaceAll("//", "/");
        return new File(path);
    }

    private Map<String, Object> getGetParamsFromChannel(FullHttpRequest fullHttpRequest) {
        Map<String, Object> params = new HashMap<>();
        if(fullHttpRequest.method() == HttpMethod.GET){
            QueryStringDecoder decoder = new QueryStringDecoder(fullHttpRequest.uri());
            Map<String, List<String>> paramList = decoder.parameters();

            for(Map.Entry<String, List<String>> entry : paramList.entrySet()){
                params.put(entry.getKey(),entry.getValue().get(0));
            }
            return params;
        }
        return params;
    }

}

package com.qupeng.java.demo.netty4.websocket.chat.server.handler;

import lombok.extern.slf4j.Slf4j;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;

@Slf4j
public class WebSocketServerHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {

    private MsgProcessor processor = new MsgProcessor();

    @Override
    protected void channelRead0(ChannelHandlerContext ctx,TextWebSocketFrame msg) throws Exception {
        processor.sendMsg(ctx.channel(), msg.text());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        Channel client = ctx.channel();
        String addr = processor.getAddress(client);
        log.info("WebSocket Client:" + addr + "异常");
        // 当出现异常就关闭连接
        cause.printStackTrace();
        ctx.close();
    }

}

package com.qupeng.java.demo.netty4.websocket.chat.server.handler;

import com.alibaba.fastjson.JSONObject;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMDecoder;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMEncoder;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMMessage;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMP;
import io.netty.channel.Channel;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.AttributeKey;
import io.netty.util.concurrent.GlobalEventExecutor;

/**
 * 主要用于自定义协议内容的逻辑处理
 *
 */
public class MsgProcessor {

	//记录在线用户
	private static ChannelGroup onlineUsers = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
	
	//定义一些扩展属性
	public static final AttributeKey<String> NICK_NAME = AttributeKey.valueOf("nickName");
	public static final AttributeKey<String> IP_ADDR = AttributeKey.valueOf("ipAddr");
	public static final AttributeKey<JSONObject> ATTRS = AttributeKey.valueOf("attrs");
	public static final AttributeKey<String> FROM = AttributeKey.valueOf("from");
	
	//自定义解码器
	private IMDecoder decoder = new IMDecoder();
	//自定义编码器
	private IMEncoder encoder = new IMEncoder();
	
	/**
	 * 获取用户昵称
	 * @param client
	 * @return
	 */
	public String getNickName(Channel client){
		return client.attr(NICK_NAME).get();
	}
	/**
	 * 获取用户远程IP地址
	 * @param client
	 * @return
	 */
	public String getAddress(Channel client){
		return client.remoteAddress().toString().replaceFirst("/","");
	}
	
	/**
	 * 获取扩展属性
	 * @param client
	 * @return
	 */
	public JSONObject getAttrs(Channel client){
		try{
			return client.attr(ATTRS).get();
		}catch(Exception e){
			return null;
		}
	}
	
	/**
	 * 获取扩展属性
	 * @param client
	 * @return
	 */
	private void setAttrs(Channel client, String key, Object value){
		try{
			JSONObject json = client.attr(ATTRS).get();
			json.put(key, value);
			client.attr(ATTRS).set(json);
		}catch(Exception e){
			JSONObject json = new JSONObject();
			json.put(key, value);
			client.attr(ATTRS).set(json);
		}
	}
	
	/**
	 * 登出通知
	 * @param client
	 */
	public void logout(Channel client, String nickname){
		//如果nickName为null，没有遵从聊天协议的连接，表示未非法登录
//		if(getNickName(client) == null){ return; }
		for (Channel channel : onlineUsers) {
			IMMessage request = new IMMessage(IMP.SYSTEM.getName(), sysTime(), onlineUsers.size(), nickname + "离开");
			String content = encoder.encode(request);
			channel.writeAndFlush(new TextWebSocketFrame(content));
		}
		onlineUsers.remove(client);
	}
	
	/**
	 * 发送消息
	 * @param client
	 * @param msg
	 */
	public void sendMsg(Channel client, IMMessage msg){

		sendMsg(client,encoder.encode(msg));
	}
	
	/**
	 * 发送消息
	 * @param client
	 * @param msg
	 */
	public void sendMsg(Channel client, String msg){

		IMMessage request = decoder.decode(msg);
		if(null == request){ return; }
		
		String addr = getAddress(client);
		
		if(request.getCmd().equals(IMP.LOGIN.getName())){
			client.attr(NICK_NAME).getAndSet(request.getSender());
			client.attr(IP_ADDR).getAndSet(addr);
			client.attr(FROM).getAndSet(request.getTerminal());
//			System.out.println(client.attr(FROM).get());
			onlineUsers.add(client);
			
			for (Channel channel : onlineUsers) {
				boolean isself = (channel == client);
				if(!isself){
					request = new IMMessage(IMP.SYSTEM.getName(), sysTime(), onlineUsers.size(), getNickName(client) + "加入");
				}else{
					request = new IMMessage(IMP.SYSTEM.getName(), sysTime(), onlineUsers.size(), "已与服务器建立连接！");
				}

				if("Console".equals(channel.attr(FROM).get())){
					channel.writeAndFlush(request);
					continue;
				}
				String content = encoder.encode(request);
				channel.writeAndFlush(new TextWebSocketFrame(content));
			}
		}else if(request.getCmd().equals(IMP.CHAT.getName())){
			for (Channel channel : onlineUsers) {
				boolean isself = (channel == client);
				if (isself) {
					request.setSender("you");
				}else{
					request.setSender(getNickName(client));
				}
				request.setTime(sysTime());

				if("Console".equals(channel.attr(FROM).get()) & !isself){
					channel.writeAndFlush(request);
					continue;
				}
				String content = encoder.encode(request);
				channel.writeAndFlush(new TextWebSocketFrame(content));
			}
		}else if(request.getCmd().equals(IMP.FLOWER.getName())){
			JSONObject attrs = getAttrs(client);
			long currTime = sysTime();
			if(null != attrs){
				long lastTime = attrs.getLongValue("lastFlowerTime");
				//60秒之内不允许重复刷鲜花
				int secends = 10;
				long sub = currTime - lastTime;
				if(sub < 1000 * secends){
					request.setSender("you");
					request.setCmd(IMP.SYSTEM.getName());
					request.setContent("您送鲜花太频繁," + (secends - Math.round(sub / 1000)) + "秒后再试");

					String content = encoder.encode(request);
					client.writeAndFlush(new TextWebSocketFrame(content));
					return;
				}
			}
			
			//正常送花
			for (Channel channel : onlineUsers) {
				if (channel == client) {
					request.setSender("you");
					request.setContent("你给大家送了一波鲜花雨");
					setAttrs(client, "lastFlowerTime", currTime);
				}else{
					request.setSender(getNickName(client));
					request.setContent(getNickName(client) + "送来一波鲜花雨");
				}
				request.setTime(sysTime());
				
				String content = encoder.encode(request);
				channel.writeAndFlush(new TextWebSocketFrame(content));
			}
		}
	}
	
	/**
	 * 获取系统时间
	 * @return
	 */
	private Long sysTime(){
		return System.currentTimeMillis();
	}
	
}

控制台客户端：

package com.qupeng.java.demo.netty4.websocket.chat.client;

import com.qupeng.java.demo.netty4.websocket.chat.client.handler.ChatClientHandler;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMDecoder;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMEncoder;
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;

import java.io.IOException;

/**
 * 客户端
 * @author Tom
 *
 */
public class ChatClient  {
    
    private ChatClientHandler clientHandler;
    private String host;
    private int port;
    
    public ChatClient(String nickName){
        this.clientHandler = new ChatClientHandler(nickName);
    }
    
    public void connect(String host,int port){
    		this.host = host;
    		this.port = port;

        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new IMDecoder());
                    ch.pipeline().addLast(new IMEncoder());
                    ch.pipeline().addLast(clientHandler);
                }
            });
            ChannelFuture f = b.connect(this.host, this.port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
    
    
    public static void main(String[] args) throws IOException{
		new ChatClient("Cover").connect("127.0.0.1",8080);
    	
    	String url = "http://localhost:8080/images/a.png";
    	System.out.println(url.toLowerCase().matches(".*\\.(gif|png|jpg)$"));
		
    }
    
}

package com.qupeng.java.demo.netty4.websocket.chat.client.handler;

import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMMessage;
import com.qupeng.java.demo.netty4.websocket.chat.protocol.IMP;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 聊天客户端逻辑实现
 * @author Tom
 *
 */
@Slf4j
public class ChatClientHandler extends SimpleChannelInboundHandler<IMMessage> {

	private ChannelHandlerContext ctx;
	private String nickName;
	public ChatClientHandler(String nickName){
		this.nickName = nickName;
	}
	
	/**启动客户端控制台*/
    private void session() throws IOException {
    		new Thread(){
    			public void run(){
					System.out.println(nickName + ",你好，请在控制台输入对话内容");
    				IMMessage message = null;
    		        Scanner scanner = new Scanner(System.in);
    		        do{
    			        	if(scanner.hasNext()){
    			        		String input = scanner.nextLine();
    			        		if("exit".equals(input)){
    			        			message = new IMMessage(IMP.LOGOUT.getName(),"Console",System.currentTimeMillis(),nickName);
    			        		}else{
    			        			message = new IMMessage(IMP.CHAT.getName(),System.currentTimeMillis(),nickName,input);
    			        		}
    			        	}
    		        }
    		        while (sendMsg(message));
    		        scanner.close();
    			}
    		}.start();
    }
	
    /**
     * tcp链路建立成功后调用
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    		this.ctx = ctx;
        IMMessage message = new IMMessage(IMP.LOGIN.getName(),"Console",System.currentTimeMillis(),this.nickName);
        sendMsg(message);
        log.info("成功连接服务器,已执行登录动作");
        session();
    }
    /**
     * 发送消息
     * @param msg
     * @return
     * @throws IOException 
     */
    private boolean sendMsg(IMMessage msg){
        ctx.channel().writeAndFlush(msg);
		System.out.println("继续输入开始对话...");
        return msg.getCmd().equals(IMP.LOGOUT) ? false : true;
    }
    /**
     * 收到消息后调用
     * @throws IOException 
     */
    @Override
    public void channelRead0(ChannelHandlerContext ctx, IMMessage msg) throws IOException {
    	IMMessage m = (IMMessage)msg;
		System.out.println((null == m.getSender() ? "" : (m.getSender() + ":")) + removeHtmlTag(m.getContent()));
    }


	public static String removeHtmlTag(String htmlStr){
		String regEx_script="<script[^>]*?>[\\s\\S]*?<\\/script>"; //定义script的正则表达式
		String regEx_style="<style[^>]*?>[\\s\\S]*?<\\/style>"; //定义style的正则表达式
		String regEx_html="<[^>]+>"; //定义HTML标签的正则表达式

		Pattern p_script=Pattern.compile(regEx_script,Pattern.CASE_INSENSITIVE);
		Matcher m_script=p_script.matcher(htmlStr);
		htmlStr=m_script.replaceAll(""); //过滤script标签

		Pattern p_style=Pattern.compile(regEx_style,Pattern.CASE_INSENSITIVE);
		Matcher m_style=p_style.matcher(htmlStr);
		htmlStr=m_style.replaceAll(""); //过滤style标签

		Pattern p_html=Pattern.compile(regEx_html,Pattern.CASE_INSENSITIVE);
		Matcher m_html=p_html.matcher(htmlStr);
		htmlStr=m_html.replaceAll(""); //过滤html标签

		return htmlStr.trim(); //返回文本字符串
	}

    /**
     * 发生异常时调用
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
    	log.info("与服务器断开连接:"+cause.getMessage());
        ctx.close();
    }
}

package com.qupeng.java.demo.netty4.websocket.chat.protocol;


/**
 * 自定义IM协议，Instant Messaging Protocol即时通信协议
 *
 */
public enum IMP {
	/** 系统消息 */
	SYSTEM("SYSTEM"),
	/** 登录指令 */
	LOGIN("LOGIN"),
	/** 登出指令 */
	LOGOUT("LOGOUT"),
	/** 聊天消息 */
	CHAT("CHAT"),
	/** 送鲜花 */
	FLOWER("FLOWER");

	private String name;
	
	public static boolean isIMP(String content){
		return content.matches("^\\[(SYSTEM|LOGIN|LOGOUT|CHAT)\\]");
	}
	
	IMP(String name){
		this.name = name;
	}
	
	public String getName(){
		return this.name;
	}
	
	public String toString(){
		return this.name;
	}
	
}

package com.qupeng.java.demo.netty4.websocket.chat.protocol;

import lombok.Data;
import org.msgpack.annotation.Message;


/**
 * 自定义消息实体类
 *
 */
@Message
@Data
public class IMMessage{
	
	private String addr;		//IP地址及端口
	private String cmd;		//命令类型[LOGIN]或者[SYSTEM]或者[LOGOUT]
	private long time;		//命令发送时间
	private int online;		//当前在线人数
	private String sender;  //发送人
	private String receiver;	//接收人
	private String content;		//消息内容
	private String terminal; 	//终端
	
	public IMMessage(){}
	
	public IMMessage(String cmd,long time,int online,String content){
		this.cmd = cmd;
		this.time = time;
		this.online = online;
		this.content = content;
		this.terminal = terminal;
	}

	public IMMessage(String cmd,String terminal,long time,String sender){
		this.cmd = cmd;
		this.time = time;
		this.sender = sender;
		this.terminal = terminal;
	}


	public IMMessage(String cmd,long time,String sender,String content){
		this.cmd = cmd;
		this.time = time;
		this.sender = sender;
		this.content = content;
		this.terminal = terminal;
	}

	@Override
	public String toString() {
		return "IMMessage{" +
				"addr='" + addr + '\'' +
				", cmd='" + cmd + '\'' +
				", time=" + time +
				", online=" + online +
				", sender='" + sender + '\'' +
				", receiver='" + receiver + '\'' +
				", content='" + content + '\'' +
				'}';
	}
}

package com.qupeng.java.demo.netty4.websocket.chat.protocol;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import org.msgpack.MessagePack;
import org.msgpack.MessageTypeException;

import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 自定义IM协议的编码器
 */
public class IMDecoder extends ByteToMessageDecoder {

	//解析IM写一下请求内容的正则
	private Pattern pattern = Pattern.compile("^\\[(.*)\\](\\s\\-\\s(.*))?");
	
	@Override
	protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
		try{
			//先获取可读字节数
	        final int length = in.readableBytes();
	        final byte[] array = new byte[length];
	        String content = new String(array,in.readerIndex(),length);
	        
	        //空消息不解析
	        if(!(null == content || "".equals(content.trim()))){
	        	if(!IMP.isIMP(content)){
	        		ctx.channel().pipeline().remove(this);
	        		return;
	        	}
	        }
	        
	        in.getBytes(in.readerIndex(), array, 0, length);
	        out.add(new MessagePack().read(array,IMMessage.class));
	        in.clear();
		}catch(MessageTypeException e){
			ctx.channel().pipeline().remove(this);
		}
	}
	
	/**
	 * 字符串解析成自定义即时通信协议
	 * @param msg
	 * @return
	 */
	public IMMessage decode(String msg){
		if(null == msg || "".equals(msg.trim())){ return null; }
		try{
			Matcher m = pattern.matcher(msg);
			String header = "";
			String content = "";
			if(m.matches()){
				header = m.group(1);
				content = m.group(3);
			}
			
			String [] heards = header.split("\\]\\[");
			long time = 0;
			try{ time = Long.parseLong(heards[1]); } catch(Exception e){}
			String nickName = heards[2];
			//昵称最多十个字
			nickName = nickName.length() < 10 ? nickName : nickName.substring(0, 9);
			
			if(msg.startsWith("[" + IMP.LOGIN.getName() + "]")){
				return new IMMessage(heards[0],heards[3],time,nickName);
			}else if(msg.startsWith("[" + IMP.CHAT.getName() + "]")){
				return new IMMessage(heards[0],time,nickName,content);
			}else if(msg.startsWith("[" + IMP.FLOWER.getName() + "]")){
				return new IMMessage(heards[0],heards[3],time,nickName);
			}else{
				return null;
			}
		}catch(Exception e){
			e.printStackTrace();
			return null;
		}
	}
}

package com.qupeng.java.demo.netty4.websocket.chat.protocol;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import org.msgpack.MessagePack;

/**
 * 自定义IM协议的编码器
 */
public class IMEncoder extends MessageToByteEncoder<IMMessage> {

	@Override
	protected void encode(ChannelHandlerContext ctx, IMMessage msg, ByteBuf out)
			throws Exception {
		out.writeBytes(new MessagePack().write(msg));
	}
	
	public String encode(IMMessage msg){
		if(null == msg){ return ""; }
		String prex = "[" + msg.getCmd() + "]" + "[" + msg.getTime() + "]";
		if(IMP.LOGIN.getName().equals(msg.getCmd()) ||
			IMP.FLOWER.getName().equals(msg.getCmd())){
			prex += ("[" + msg.getSender() + "][" + msg.getTerminal() + "]");
		}else if(IMP.CHAT.getName().equals(msg.getCmd())){
			prex += ("[" + msg.getSender() + "]");
		}else if(IMP.SYSTEM.getName().equals(msg.getCmd())){
			prex += ("[" + msg.getOnline() + "]");
		}
		if(!(null == msg.getContent() || "".equals(msg.getContent()))){
			prex += (" - " + msg.getContent());
		}
		return prex;
	}

}

页面：

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=0" name="viewport">
    <title>在线聊天室</title>
    <link rel="stylesheet" type="text/css" href="css/style.css" />
    <script type="text/javascript" src="/js/lib/jquery.min.js"></script>
	<script type="text/javascript" src="/js/lib/jquery.snowfall.js"></script>
	<script type="text/javascript" src="/js/chat.util.js"></script>
</head>

<body>
	<div id="loginbox">
        <div style="width:300px;margin:200px auto;">
           	 欢迎进入WebSocket聊天室
            <br/>
            <br/>
            <input type="text" style="width:180px;" placeholder="进入前，请先输入昵称" id="nickname" name="nickname" />
            <input type="button" style="width:50px;" value="进入" onclick="CHAT.login();" />
            <div id="error-msg" style="color:red;"></div>
        </div>
    </div>
    <div id="chatbox" style="display: none;">
        <div style="background:#3d3d3d;height: 28px; width: 100%;font-size:12px;position: fixed;top: 0px;z-index: 999;">
            <div style="line-height: 28px;color:#fff;">
                <span style="text-align:left;margin-left:10px;">Netty Websocket聊天室</span>
                <span style="float:right; margin-right:10px;">
                	<span>当前在线<span id="onlinecount">0</span>人</span> |
	                <span id="shownikcname">匿名</span> |
	                <a href="javascript:;" onclick="CHAT.logout()" style="color:#fff;">退出</a>
                </span>
            </div>
        </div>
        <div id="doc">
            <div id="chat">
                <div id="message" class="message">
                    <div id="onlinemsg" style="background:#EFEFF4; font-size:12px; margin-top:40px; margin-left:10px; color:#666;">
                    </div>
                </div>
                <form onsubmit="return false;">
                	<div class="tool-box">
                		<div class="face-box" id="face-box"></div>
                		<span class="face" onclick="CHAT.openFace()" title="选择表情"></span>
                		<!--
	                		<span class="img" id="tool-img-btn" title="发送图片"></span>
	                		<span class="file" id="tool-file-btn" title="上传文件"></span>
                		 -->
                		<span class="flower" onclick="CHAT.sendFlower()" title="送鲜花"></span>
                	</div>
                	<div class="input-box">
		                <div class="input" contenteditable="true" id="send-message"></div>
		                <div class="action">
		                    <input class="button" type="button" id="mjr_send" onclick="CHAT.sendText()" value="发送"/>
		                </div>
            		</div>
               </form>
           </div>
       </div>
    </div>
</body>

</html>

pom文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.qupeng.java.demos</groupId>
    <artifactId>netty4</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.52.Final</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.25</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.4</version>
        </dependency>

        <dependency>
            <groupId>org.msgpack</groupId>
            <artifactId>msgpack</artifactId>
            <version>0.6.12</version>
        </dependency>

        <dependency>
            <groupId>org.dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>2.0.0</version>
        </dependency>
    </dependencies>
</project>