netty上手

关于netty的基础NIO，请参见：NIO原理及实例

下面介绍Netty的上手使用；

首先为项目添加jar依赖：

<dependency>
   <groupId>io.netty</groupId>
   <artifactId>netty-all</artifactId>
   <version>4.1.8.Final</version>
</dependency>

1、开始写代码，一般是先写输入输出的逻辑（handler）

　　handler一般继承于SimpleChannelInboundHandler 或者 ChannelOutboundHandlerAdapter，区别在于simple。。不需要手动释放消息

　　输入handler 继承于SimpleChannelInboundHandler

package com.pt.netty.client;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * @author panteng
 * @description 继承自simple会自动释放数据，否则需要手动释放
 * @date 17-3-19.
 */
@ChannelHandler.Sharable
public class InputHandler1 extends SimpleChannelInboundHandler<ByteBuf> {

    /**
     * 读数据
     *
     * @param channelHandlerContext
     * @param byteBuf
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf) throws Exception {
        System.out.println("InputHandler1：channelRead0");
    }

    /**
     * 读数据，首先调此函数，父类默认调用channelRead0
     *
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("InputHandler1：channelRead");
        if (msg instanceof ByteBuf) {
            System.out.println(new String(ByteBufUtil.getBytes((ByteBuf) msg)));
        }
        ctx.writeAndFlush(Unpooled.copiedBuffer("OK".getBytes()));
        ctx.fireChannelRead(msg);
        // super.channelRead(ctx, msg);
    }
    /**
     * 连接成功
     *
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("InputHandler1：channelActive 连接成功");
        // super.channelActive(ctx);
    }

    /**
     * 异常处理
     *
     * @param ctx
     * @param cause
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
        super.exceptionCaught(ctx, cause);
    }
}

InputHandler1

package com.pt.netty.client;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * @author panteng
 * @description 继承自simple会自动释放数据，否则需要手动释放
 * @date 17-3-19.
 */
@ChannelHandler.Sharable
public class InputHandler2 extends SimpleChannelInboundHandler<ByteBuf> {

    /**
     * 读数据
     *
     * @param channelHandlerContext
     * @param byteBuf
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf) throws Exception {
        System.out.println("InputHandler2：channelRead0");
    }

    /**
     * 读数据，首先调此函数，父类默认调用channelRead0
     *
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("InputHandler2：channelRead");
        // super.channelRead(ctx, msg);
    }

    /**
     * 连接成功
     *
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("InputHandler2：channelActive 连接成功");
        // super.channelActive(ctx);
    }

    /**
     * 异常处理
     *
     * @param ctx
     * @param cause
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
        super.exceptionCaught(ctx, cause);
    }
}

InputHandler2

　　输出handler

package com.pt.netty.client;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPromise;

/**
 * 继承ChannelOutboundHandlerAdapter方法时，必须执行super.方法，否则阻塞无法执行
 *
 * @author panteng
 * @description
 * @date 17-3-19.
 */
public class OutputHandler extends ChannelOutboundHandlerAdapter {
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        // super.write(ctx, msg, promise);
        System.out.println("OutputHandler:write");
        ctx.write(msg);

    }
}

OutputHandler

2、main函数

package com.pt.netty.client;

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

/**
 * @author panteng
 * @description
 * @date 17-3-19.
 */
public class ClientOfNetty {
    public static void main(String[] arges) {
        // 可以指定线程数目（不指定采用默认值 CPU的2倍）
        EventLoopGroup group = new NioEventLoopGroup(1);
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group).channel(NioSocketChannel.class).remoteAddress("10.232.36.21", 4700)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new OutputHandler());
                            socketChannel.pipeline().addLast(new InputHandler1());
                            socketChannel.pipeline().addLast(new InputHandler2());
                        }
                    });
            ChannelFuture f = bootstrap.connect().sync();// 阻塞
            Thread.sleep(5000);
            f.channel().close().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
        System.out.println("退出主函数。。。 。。。");
    }
}

ClientOfNetty