Java后端进阶-网络编程（Netty零拷贝机制）

package com.study.hc.net.netty.demo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import org.junit.Test;

import java.util.Arrays;

/**
 * bytebuf的常规API操作示例
 */
public class ByteBufDemo {
    @Test
    public void apiTest() {
        //  +-------------------+------------------+------------------+
        //  | discardable bytes |  readable bytes  |  writable bytes  |
        //  |                   |     (CONTENT)    |                  |
        //  +-------------------+------------------+------------------+
        //  |                   |                  |                  |
        //  0      <=       readerIndex   <=   writerIndex    <=    capacity

        // 1.创建一个非池化的ByteBuf，大小为10个字节
        ByteBuf buf = Unpooled.buffer(10);
        System.out.println("原始ByteBuf为====================>" + buf.toString());
        System.out.println("1.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 2.写入一段内容
        byte[] bytes = {1, 2, 3, 4, 5};
        buf.writeBytes(bytes);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
        System.out.println("2.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 3.读取一段内容
        byte b1 = buf.readByte();
        byte b2 = buf.readByte();
        System.out.println("读取的bytes为====================>" + Arrays.toString(new byte[]{b1, b2}));
        System.out.println("读取一段内容后ByteBuf为===========>" + buf.toString());
        System.out.println("3.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 4.将读取的内容丢弃
        buf.discardReadBytes();
        System.out.println("将读取的内容丢弃后ByteBuf为========>" + buf.toString());
        System.out.println("4.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 5.清空读写指针
        buf.clear();
        System.out.println("将读写指针清空后ByteBuf为==========>" + buf.toString());
        System.out.println("5.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 6.再次写入一段内容，比第一段内容少
        byte[] bytes2 = {1, 2, 3};
        buf.writeBytes(bytes2);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes2));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
        System.out.println("6.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 7.将ByteBuf清零
        buf.setZero(0, buf.capacity());
        System.out.println("将内容清零后ByteBuf为==============>" + buf.toString());
        System.out.println("7.ByteBuf中的内容为================>" + Arrays.toString(buf.array()) + "\n");

        // 8.再次写入一段超过容量的内容
        byte[] bytes3 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
        buf.writeBytes(bytes3);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes3));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
        System.out.println("8.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");
        //  随机访问索引 getByte
        //  顺序读 read*
        //  顺序写 write*
        //  清除已读内容 discardReadBytes
        //  清除缓冲区 clear
        //  搜索操作
        //  标记和重置
        //  完整代码示例：参考
        // 搜索操作 读取指定位置 buf.getByte(1);
        //
    }

}

会动态扩容

DirectByteBufDemo

package com.study.hc.net.netty.demo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import org.junit.Test;

import java.util.Arrays;

/**
 * 堆外内存的常规API操作示例
 */
public class DirectByteBufDemo {
    @Test
    public void apiTest() {
        //  +-------------------+------------------+------------------+
        //  | discardable bytes |  readable bytes  |  writable bytes  |
        //  |                   |     (CONTENT)    |                  |
        //  +-------------------+------------------+------------------+
        //  |                   |                  |                  |
        //  0      <=       readerIndex   <=   writerIndex    <=    capacity

        // 1.创建一个非池化的ByteBuf，大小为10个字节
        ByteBuf buf = Unpooled.directBuffer(10);
        System.out.println("原始ByteBuf为====================>" + buf.toString());
        // System.out.println("1.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 2.写入一段内容
        byte[] bytes = {1, 2, 3, 4, 5};
        buf.writeBytes(bytes);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
        //System.out.println("2.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 3.读取一段内容
        byte b1 = buf.readByte();
        byte b2 = buf.readByte();
        System.out.println("读取的bytes为====================>" + Arrays.toString(new byte[]{b1, b2}));
        System.out.println("读取一段内容后ByteBuf为===========>" + buf.toString());
       //System.out.println("3.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 4.将读取的内容丢弃
        buf.discardReadBytes();
        System.out.println("将读取的内容丢弃后ByteBuf为========>" + buf.toString());
        //System.out.println("4.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 5.清空读写指针
        buf.clear();
        System.out.println("将读写指针清空后ByteBuf为==========>" + buf.toString());
        //System.out.println("5.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 6.再次写入一段内容，比第一段内容少
        byte[] bytes2 = {1, 2, 3};
        buf.writeBytes(bytes2);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes2));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
       // System.out.println("6.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");

        // 7.将ByteBuf清零
        buf.setZero(0, buf.capacity());
        System.out.println("将内容清零后ByteBuf为==============>" + buf.toString());
       // System.out.println("7.ByteBuf中的内容为================>" + Arrays.toString(buf.array()) + "\n");

        // 8.再次写入一段超过容量的内容
        byte[] bytes3 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
        buf.writeBytes(bytes3);
        System.out.println("写入的bytes为====================>" + Arrays.toString(bytes3));
        System.out.println("写入一段内容后ByteBuf为===========>" + buf.toString());
       // System.out.println("8.ByteBuf中的内容为===============>" + Arrays.toString(buf.array()) + "\n");
        //  随机访问索引 getByte
        //  顺序读 read*
        //  顺序写 write*
        //  清除已读内容 discardReadBytes
        //  清除缓冲区 clear
        //  搜索操作
        //  标记和重置
        //  完整代码示例：参考
        // 搜索操作 读取指定位置 buf.getByte(1);
        //
    }

}

package com.study.hc.net.netty.demo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.CompositeByteBuf;
import io.netty.buffer.Unpooled;

import java.nio.charset.Charset;

/**
 * 零拷贝示例
 */
public class ZeroCopyTest {
    @org.junit.Test
    public void wrapTest() {
        byte[] arr = {1, 2, 3, 4, 5};
        ByteBuf byteBuf = Unpooled.wrappedBuffer(arr);
        System.out.println(byteBuf.getByte(4));
        arr[4] = 6;
        System.out.println(byteBuf.getByte(4));
    }

    @org.junit.Test
    public void sliceTest() {
        ByteBuf buffer1 = Unpooled.wrappedBuffer("hello".getBytes());
        ByteBuf newBuffer = buffer1.slice(1, 2);
        newBuffer.unwrap();
        System.out.println(newBuffer.toString());
    }

    @org.junit.Test
    public void compositeTest() {
        ByteBuf buffer1 = Unpooled.buffer(3);
        buffer1.writeByte(1);
        ByteBuf buffer2 = Unpooled.buffer(3);
        buffer2.writeByte(4);
        CompositeByteBuf compositeByteBuf = Unpooled.compositeBuffer();
        CompositeByteBuf newBuffer = compositeByteBuf.addComponents(true, buffer1, buffer2);
        System.out.println(newBuffer);
    }

}

案例设计——推送功能实现以及百万连接优化

用zookeeper可以替换注册中心负载均衡

代码实现一下

package com.study.netty.push.test;

import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TonySocketServer {
    public static void main(String[] args) throws IOException, Exception {
        // server
        ServerSocket serverSocket = new ServerSocket(9999);

        // 获取新连接
        while (true) {
            final Socket accept = serverSocket.accept();
            InputStream inputStream = accept.getInputStream();
            while (true) {
                byte[] request = new byte[1024];
                int read = inputStream.read(request);
                if (read == -1) {
                    break;
                }
                // 得到请求内容，解析，得到发送对象和发送内容
                String content = new String(request);
                System.out.println(content);
            }
        }
    }
}

package com.study.netty.push.test;

import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.util.concurrent.CountDownLatch;

public class TonySocketClient {
    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 9999);
        OutputStream outputStream = socket.getOutputStream();

        // 消息长度固定为 220字节，包含有
        // 1. 目标用户ID长度为10， 10 000 000 000 ~ 19 999 999 999
        // 2. 消息内容字符串长度最多70。 按一个汉字3字节，内容的最大长度为210字节
        byte[] request = new byte[220];
        byte[] userId = "10000000000".getBytes();
        byte[] content = "我爱你tony你爱我吗我爱你tony你爱我吗我爱你tony你爱我吗我爱你tony你爱我吗".getBytes();
        System.arraycopy(userId, 0, request, 0, 10);
        System.arraycopy(content, 0, request, 10, content.length);

        CountDownLatch countDownLatch = new CountDownLatch(10);
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                try {
                    outputStream.write(request);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                countDownLatch.countDown();
            }).start();
        }

        countDownLatch.await();
        Thread.sleep(2000L); // 两秒后退出
        socket.close();
    }
}

java13没有出现这样的问题，很神奇

需要进行解码和编码

用Netty实现！

package com.study.netty.push.netty;

import io.netty.bootstrap.ServerBootstrap;
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.LineBasedFrameDecoder;

public class XNettyServer {
    public static void main(String[] args) throws Exception {
        // 1、 线程定义
        // accept 处理连接的线程池
        EventLoopGroup acceptGroup = new NioEventLoopGroup();
        // read io 处理数据的线程池
        EventLoopGroup readGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(acceptGroup, readGroup);
            // 2、 选择TCP协议，NIO的实现方式
            b.channel(NioServerSocketChannel.class);
            b.childHandler(new ChannelInitializer<SocketChannel>() {

                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    // 3、 职责链定义（请求收到后怎么处理）
                    ChannelPipeline pipeline = ch.pipeline();
                    // TODO 3.1 增加解码器
                    pipeline.addLast(new XDecoder());
                    // TODO 3.2 打印出内容 handdler
                    pipeline.addLast(new XHandller());
                }
            });
            // 4、 绑定端口
            System.out.println("启动成功，端口 9999");
            b.bind(9999).sync().channel().closeFuture().sync();
        } finally {
            acceptGroup.shutdownGracefully();
            readGroup.shutdownGracefully();
        }
    }
}

package com.study.netty.push.netty;

import java.util.List;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

public class XDecoder extends ByteToMessageDecoder {
    static final int PACKET_SIZE = 220;

    // 用来临时保留没有处理过的请求报文
    ByteBuf tempMsg = Unpooled.buffer();

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        System.out.println("收到了一次数据包，长度是：" + in.readableBytes());
        // in 请求的数据
        // out 将粘在一起的报文拆分后的结果保留起来

        // 1、 合并报文
        ByteBuf message = null;
        int tmpMsgSize = tempMsg.readableBytes();
        // 如果暂存有上一次余下的请求报文，则合并
        if (tmpMsgSize > 0) {
            message = Unpooled.buffer();
            message.writeBytes(tempMsg);
            message.writeBytes(in);
            System.out.println("合并：上一数据包余下的长度为：" + tmpMsgSize + ",合并后长度为:" + message.readableBytes());
        } else {
            message = in;
        }

        // 2、 拆分报文
        // 这个场景下，一个请求固定长度为3，可以根据长度来拆分
        // i+1 i+1 i+1 i+1 i+1
        // 不固定长度，需要应用层协议来约定 如何计算长度
        // 在应用层中，根据单个报文的长度及特殊标记，来将报文进行拆分或合并
        // dubbo rpc协议 = header(16) + body(不固定)
        // header最后四个字节来标识body
        // 长度 = 16 + body长度
        // 0xda, 0xbb 魔数

        int size = message.readableBytes();
        int counter = size / PACKET_SIZE;
        for (int i = 0; i < counter; i++) {
            byte[] request = new byte[PACKET_SIZE];
            // 每次从总的消息中读取3个字节的数据
            message.readBytes(request);

            // 将拆分后的结果放入out列表中，交由后面的业务逻辑去处理
            out.add(Unpooled.copiedBuffer(request));
        }

        // 3、多余的报文存起来
        // 第一个报文： i+  暂存
        // 第二个报文： 1 与第一次
        size = message.readableBytes();
        if (size != 0) {
            System.out.println("多余的数据长度：" + size);
            // 剩下来的数据放到tempMsg暂存
            tempMsg.clear();
            tempMsg.writeBytes(message.readBytes(size));
        }

    }

}

package com.study.netty.push.netty;

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

/**
 * 后续处理handdler
 */
public class XHandller extends ChannelInboundHandlerAdapter {

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

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // 输出 bytebuf
        ByteBuf buf = (ByteBuf) msg;
        byte[] content = new byte[buf.readableBytes()];
        buf.readBytes(content);
        System.out.println(new String(content));
    }

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

}

优化百万连接

案例2——Netty在网易内部的实践