使用Maven的话请在pom.xml中注入netty依赖
<!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.43.Final</version>
</dependency>NettyClient
package com.ronnie.netty.sample;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
public class NettyClient {
public static void main(String[] args) throws InterruptedException {
// 客户端需要一个事件循环组
NioEventLoopGroup group = new NioEventLoopGroup();
try {
// 创建客户端启动对象
// 注意: 客户端使用的不是 ServerBootstrap 而是 Bootstrap
Bootstrap bootstrap = new Bootstrap();
// 设置相关参数
bootstrap.group(group) //设置线程组
.channel(NioSocketChannel.class) // 设置客户端通道实现类(反射)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new NettyClientHandler()); // 加入自己的处理器
}
});
System.out.println("Client side is ready......");
// 启动客户端去连接服务器端
// channelFuture涉及到netty的异步模型
ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 6668).sync();
// 给关闭通道进行监听
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
group.shutdownGracefully();
}
}
}
NettyClientHandler
package com.ronnie.netty.sample;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;
public class NettyClientHandler extends ChannelInboundHandlerAdapter {
// 当同道就绪, 就会触发该方法
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("Client " + ctx);
ctx.writeAndFlush(Unpooled.copiedBuffer("Hello, server: ROFL", CharsetUtil.UTF_8));
}
/**
* 当通道有读取事件时会触发
* @param ctx
* @param msg
* @throws Exception
*/
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
ByteBuf buf = (ByteBuf) msg;
System.out.println("The message server responded: " + buf.toString(CharsetUtil.UTF_8));
System.out.println("Server address: " + ctx.channel().remoteAddress());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
NettyServer
package com.ronnie.netty.sample;
import io.netty.bootstrap.ServerBootstrap;
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.NioServerSocketChannel;
public class NettyServer {
public static void main(String[] args) throws InterruptedException {
// 创建 BossGroup 与 WorkerGroup
/**
* 1. 创建两个线程组 bossGroup 和 workerGroup
* 2. bossGroup 只是处理连接请求, 真正的和客户端业务处理, 会交给workGroup完成
* 3. 两个都是无限循环
* 4. bossGroup 和 workerGroup 含有的子线程(NioEventLoop)的个数
* 为默认实际 cpu核数 * 2
*/
NioEventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
// 创建服务器端的启动对象, 配置参数
ServerBootstrap bootstrap = new ServerBootstrap();
// 使用链式编程来进行设置
bootstrap.group(bossGroup, workerGroup) // 设置两个线程组
.channel(NioServerSocketChannel.class) // 使用NioSocketChannel 作为服务器的通道实现
.option(ChannelOption.SO_BACKLOG, 128) // 设置线程队列等待连接的个数
.childOption(ChannelOption.SO_KEEPALIVE, true) // 设置保持活动连接状态
.childHandler(new ChannelInitializer<SocketChannel>() { // 创建一个通道初始化对象(匿名对象)
/**
* 给pipeline设置处理器
* @param ch
* @throws Exception
*/
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new NettyServerHandler());
}
}); // 给workerGroup的 EventLoop 设置处理器
System.out.println("Server is ready......");
// 绑定一个端口并且同步, 生成了一个ChannelFuture对象
// 启动服务器(并绑定端口)
ChannelFuture cf = bootstrap.bind(6668).sync();
// 对关闭通道进行监听
cf.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
// 优雅地关闭
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
NettyServerHandler
package com.ronnie.netty.sample;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelPipeline;
import io.netty.util.CharsetUtil;
/**
* 1. 自定义一个Handler需要继承 netty 规定好的某个 HandlerAdapter(适配器模式)
* 2. 这时我们自定义一个Handler, 才能称为一个handler
*/
public class NettyServerHandler extends ChannelInboundHandlerAdapter {
/**
* 读取数据事件(这里我们可以读取客户端发送的消息)
* ChannelHandlerContext ctx: 上下文对象, 含有管道 pipeline, 通道 channel, 地址 address
* Object msg: 就是客户端发送的数据 默认Object
* @param ctx
* @param msg
* @throws Exception
*/
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
System.out.println("The server is reading thread: " + Thread.currentThread().getName());
System.out.println("server ctx = " + ctx);
System.out.println("Check the relationship between channel and pipeline");
Channel channel = ctx.channel();
ChannelPipeline pipeline = ctx.pipeline(); // 本质是一个双向链表, 涉及到出栈入栈问题
// 将 msg转成一个 ByteBuf(是netty提供的, 不是NIO的 ByteBuffer, 性能更高)
ByteBuf buf = (ByteBuf) msg;
System.out.println("The message that client send: " + buf.toString(CharsetUtil.UTF_8));
System.out.println("The address of client: " + ctx.channel().remoteAddress());
}
/**
* 数据读取完毕
* @param ctx
* @throws Exception
*/
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
// write + flush, 将数据写入到缓冲并刷新
// 一般来说, 我们对发送的数据进行编码
ctx.writeAndFlush(Unpooled.copiedBuffer("Hello, dear client, Kappa", CharsetUtil.UTF_8));
}
/**
* 处理异常, 一般需要关闭通道
* @param ctx
* @param cause
* @throws Exception
*/
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
}
bossGroup 和 workerGroup 含有的子线程(NioEventLoop)的个数为默认实际 cpu核数 * 2。
如果传入的为空, 默认传入0
public NioEventLoopGroup() {
this(0);
} public NioEventLoopGroup(int nThreads) {
this(nThreads, (Executor) null);
} public NioEventLoopGroup(int nThreads, Executor executor) {
this(nThreads, executor, SelectorProvider.provider());
} public NioEventLoopGroup(
int nThreads, Executor executor, final SelectorProvider selectorProvider) {
this(nThreads, executor, selectorProvider, DefaultSelectStrategyFactory.INSTANCE);
} public NioEventLoopGroup(int nThreads, Executor executor, final SelectorProvider selectorProvider,
final SelectStrategyFactory selectStrategyFactory) {
super(nThreads, executor, selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject());
} /**
* @see MultithreadEventExecutorGroup#MultithreadEventExecutorGroup(int, Executor, Object...)
*/
protected MultithreadEventLoopGroup(int nThreads, Executor executor, Object... args) {
// 如果传入的线程数为0, 就让线程数为默认事件循环线程数, 否则就使用传入的线程数
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, args);
}一路追踪源码, 最终你会追踪到:
DEFAULT_EVENT_LOOP_THREADS = Math.max(1, SystemPropertyUtil.getInt(
"io.netty.eventLoopThreads", NettyRuntime.availableProcessors() * 2));我们可以写个程序测试一下
package com.ronnie.netty.sample;
import io.netty.util.NettyRuntime;
public class Test {
public static void main(String[] args) {
System.out.println(NettyRuntime.availableProcessors());
}
}Pipeline中含有其对应的Channel的属性, Channel中也有其对应的Pipeline的属性, 两者是互相包容的, 而ChannelHandlerContext则包含了此两者, 是个很复杂的接口。
原文：https://www.cnblogs.com/ronnieyuan/p/12016712.html