**使用java編碼的springboot項目在調(diào)用C語言等其他語言編寫的Tcp接口時，使用netty框架可以實現(xiàn)數(shù)據(jù)雙向持續(xù)交互處理。
   注：在交互過程中，c語言生成的二進制字節(jié)碼轉(zhuǎn)java字符串時往往出現(xiàn)亂碼，請看后面處理方式（netty處理類中的代碼）。**

一、引入netty的jar包

io.netty
netty-all

二、使用netty框架
1、創(chuàng)建客戶端
package com.iflytek.digtal.netty;

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;

/**

• netty客戶端
  */
  public class NettyClient {

  /**

  • 連接tcp服務(wù)端初始化

  • @throws InterruptedException
    */
    public static void init() throws InterruptedException {
    //客戶端需要一個事件循環(huán)組
    NioEventLoopGroup group = new NioEventLoopGroup();

    try {
    //創(chuàng)建客戶端啟動對象
    //注意客戶端使用的不是SocketBootstrap而是Bootstrap
    Bootstrap bootstrap = new Bootstrap();

     // 設(shè)置相關(guān)參數(shù)
     bootstrap.group(group) //設(shè)置線程組
             .channel(NioSocketChannel.class)// 使用NioSocketChannel作為客戶端的通道實現(xiàn)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ch.pipeline().addLast(new NettyClientHandler());
                 }
             });
    
     System.out.println("netty client start..");
     ChannelFuture cf = bootstrap.connect("127.0.0.1", 6000).sync();
    
     cf.channel().closeFuture().sync();
    

    }finally {
    group.shutdownGracefully();
    }
    }

  public static void main(String[] args) throws InterruptedException {
  //客戶端需要一個事件循環(huán)組
  NioEventLoopGroup group = new NioEventLoopGroup();

   try {
       //創(chuàng)建客戶端啟動對象
       //注意客戶端使用的不是SocketBootstrap而是Bootstrap
       Bootstrap bootstrap = new Bootstrap();
  
       // 設(shè)置相關(guān)參數(shù)
       bootstrap.group(group) //設(shè)置線程組
               .channel(NioSocketChannel.class)// 使用NioSocketChannel作為客戶端的通道實現(xiàn)
               .handler(new ChannelInitializer<SocketChannel>() {
                   @Override
                   protected void initChannel(SocketChannel ch) throws Exception {
                       ch.pipeline().addLast(new NettyClientHandler());
                   }
               });
  
       System.out.println("netty client start..");
       ChannelFuture cf = bootstrap.connect("127.0.0.1", 6000).sync();
  
       cf.channel().closeFuture().sync();
   }finally {
       group.shutdownGracefully();
   }
  

  }

}
2、創(chuàng)建服務(wù)端
package com.iflytek.digtal.netty;

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;

public class NettyServer {

public static void main(String[] args) throws InterruptedException {
    //創(chuàng)建兩個線程組bossGroup和workerGroup，含有的子線程NioEventLoop的個數(shù)默認(rèn)是CPU的兩倍
    //bossGroup只是處理連接請求，真正的和客戶端業(yè)務(wù)處理，會交給workerGroup完成
    EventLoopGroup bossGroup = new NioEventLoopGroup(1);
    EventLoopGroup workerGroup = new NioEventLoopGroup(1);

    try {
        //創(chuàng)建服務(wù)器端的啟動對象
        ServerBootstrap bootstrap = new ServerBootstrap();
        //使用鏈?zhǔn)骄幊虂砼渲脜?shù)
        bootstrap.group(bossGroup, workerGroup)//設(shè)置兩個線程組
                .channel(NioServerSocketChannel.class)//使用NioServerSocketChannel作為服務(wù)器的通道實現(xiàn)
                //初始化服務(wù)器連接隊列大小，服務(wù)端處理客戶端連接請求是順序處理的，所以同一時間只能處理一個客戶端連接
                //多個客戶端同時來的時候，服務(wù)端將不能處理的客戶端連接請求放在隊列中等待處理
                .option(ChannelOption.SO_BACKLOG, 1024)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel channel) throws Exception {
                        //對workerGroup的SocketChannel設(shè)置處理器
                        channel.pipeline().addLast(new NettyServerHandler());
                    }
                });

        System.out.println("netty server start..");

        //綁定一個端口并且同步生成一個ChannelFuture異步對象，通過isDone()等方法可以判斷異步事件的執(zhí)行情況
        //啟動服務(wù)器（并綁定的端口），bind是異步操作，sync方法是等待異步操作執(zhí)行完畢
        ChannelFuture cf = bootstrap.bind(9000).sync();

        //給cf注冊監(jiān)聽器，監(jiān)聽我們關(guān)心的事件
        cf.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture channelFuture) throws Exception {
                if (cf.isSuccess()) {
                    System.out.println("監(jiān)聽端口9000成功");
                } else {
                    System.out.println("監(jiān)聽端口9000失敗");
                }
            }
        });
        //等待服務(wù)端監(jiān)聽端口關(guān)閉，closeFuture是異步操作
        //通過sync方法同步等待通道關(guān)閉處理完畢，這里會阻塞等待通道關(guān)閉完成，內(nèi)部調(diào)用的是Object的wait()方法
        cf.channel().closeFuture().sync();

    } finally {
        bossGroup.shutdownGracefully();
        workerGroup.shutdownGracefully();
    }

}

}
3、編寫處理類
package com.iflytek.digtal.netty2;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import lombok.extern.slf4j.Slf4j;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.util.Arrays;

/**

• 處理類
  */
  @Slf4j
  public class NettyClientHandler2 extends ChannelInboundHandlerAdapter {

  /**

  • 客戶端連接標(biāo)識
  • @param ctx
  • @throws Exception
    */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    ByteBuf buf = Unpooled.copiedBuffer(“HelloServer”.getBytes(Charset.forName(“GBK”)));
    ctx.writeAndFlush(buf);
    }

  //當(dāng)通道建立后有事件時會觸發(fā)，即服務(wù)端發(fā)送數(shù)據(jù)給客戶端
  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

   ByteBuf buf = (ByteBuf) msg;
   log.info("哈哈哈:{}",msg);
   // 復(fù)制內(nèi)容到字節(jié)數(shù)組bytes
   byte[] bytes = new byte[buf.readableBytes()];
   buf.readBytes(bytes);
   log.info("收到的數(shù)據(jù)為：{}", bytes);
  
   int[] lengthArr = {4,4,4,4,4,4,56,24,56,24,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,56,32,8};
   String[] strArr = {"int","int","int","int","int","int","char","char","char","char",
           "float","float","int","int","float","float","float","float","int","int","int","int",
           "int","int","int","int","char","char","systime"};
  
   String[] strs = new String[29];
   int offset = 0;
   for(int i =0;i<29;i++){
       byte[] bytes1 = new byte[lengthArr[i]];
       System.arraycopy(bytes, offset, bytes1, 0, lengthArr[i]);
       offset = offset + lengthArr[i];
       if("int".equals(strArr[i])){
           strs[i] = String.valueOf(bytesToInt(bytes1,0));
       }else if("char".equals(strArr[i])){
           strs[i] = bytesToChar(bytes1);
       }else if("float".equals(strArr[i])){
           strs[i] = String.valueOf(byteToFloat(bytes1,0));
       }else if("systime".equals(strArr[i])){
           strs[i] = bytesToChar(bytes1);
       }
   }
   System.out.println("二進制數(shù)據(jù)轉(zhuǎn)化后的結(jié)果："+ Arrays.toString(strs));
  
   // 前六個int數(shù)值
   String[] str = new String[6];
   for(int i =0,j=0;j<24;i++){
       str[i] = String.valueOf(bytesToInt(bytes,j));
       j = j+4;
   }
   System.out.println("str:"+ Arrays.toString(str));
  
   //第七個試驗名稱
   byte[] bytes1 = new byte[56];
   System.arraycopy(bytes, 24, bytes1, 0, 56);
  

// for(int i=0;i<56;i++){
// bytes1[i] = bytes[20+i];
// }
log.info(“試驗名稱字節(jié)數(shù)組為：{}”, bytes1);
String str1 = bytesToChar(bytes1);
System.out.println(“試驗名稱str1:”+str1);

    //第八個通道名稱
    byte[] bytes2 = new byte[24];
    System.arraycopy(bytes, 80, bytes2, 0, 24);

// for(int i=0;i<56;i++){
// bytes1[i] = bytes[20+i];
// }
log.info(“通道名稱字節(jié)數(shù)組為：{}”, bytes2);
String str2 = bytesToChar(bytes2);
System.out.println(“通道名稱str2:”+str2);

    //第九個采集名稱
    byte[] bytes3 = new byte[56];
    System.arraycopy(bytes, 104, bytes3, 0, 56);

// for(int i=0;i<56;i++){
// bytes1[i] = bytes[20+i];
// }
log.info(“采集名稱字節(jié)數(shù)組為：{}”, bytes3);
String str3 = bytesToChar(bytes3);
System.out.println(“采集名稱str3:”+str3);

    System.out.println("服務(wù)端地址是：" + ctx.channel().remoteAddress());

}

public  int combine(byte b[])
{
    int t1=(b[3]&0xff)<<24;
    int t2=(b[2]&0xff)<<16;
    int t3=(b[1]&0xff)<<8;
    int t4=b[0]&0xff;
    //System.out.println(b[1]&0xff);//輸出的是一個整形數(shù)據(jù)
    //在java中，設(shè)計int和比int位數(shù)來的小的類型b，如byte,char等，都是先把小類型擴展成int再來運算，
    //return( t1<<24)+(t2<<16)+(t3<<8)+t4;//必須加括號
    return t1+t2+t3+t4;
}

private char[] getChars (byte[] bytes) {

    Charset cs = Charset.forName ("GBK");

    ByteBuffer bb = ByteBuffer.allocate (bytes.length);

    bb.put (bytes);

    bb.flip ();

    CharBuffer cb = cs.decode (bb);

    return cb.array();

}

/**
 * byte轉(zhuǎn)int
 * @Title: bytesToInt
 *
 * @param: @param src 源數(shù)組
 * @param: @param offset 起始偏移量
 * @return: int
 */
public int bytesToInt(byte[] src, int offset) {
    int value;
    value = src[offset] & 0xFF;
    value |= ((long) (src[offset + 1] & 0xFF) << 8);
    value |= ((long) (src[offset + 2] & 0xFF) << 16);
    value |= ((long) (src[offset + 3] & 0xFF) << 24);
    return value;
}

public String bytesToChar(byte[] bytes){
    char[] chars = new char[bytes.length];
    for (int i = 0; i < bytes.length; i++) {
        chars[i] = (char) (bytes[i] & 0xFF); // 使用位運算將字節(jié)轉(zhuǎn)換為字符
    }

// for(int i =0;i<chars.length;i++){
// System.out.println(“char數(shù)組：”+chars[i]);
// }
String str = new String(chars);
// System.out.println(“轉(zhuǎn)換后的字符數(shù)組:” + str);
return str;
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    log.info("關(guān)閉通道");
    cause.printStackTrace();
    ctx.close();
}

/**
 * byte轉(zhuǎn)long
 * @Title: bytesToLong
 *
 * @param: @param src 源數(shù)組
 * @param: @param offset 起始偏移量
 * @return: long
 */
public static long bytesToLong(byte[] src, int offset) {
    long value = 0;
    for(int i = 0; i < 8; i++) {
        value |= ((long) (src[offset + i] & 0xFF) << (8 * i));
    }

    return value;
}
/**
 * byte轉(zhuǎn)float
 * @Title: byteToFloat
 *
 * @param: @param src 源數(shù)組
 * @param: @param offset 起始偏移量
 * @return: float
 */
public static float byteToFloat(byte[] src, int offset) {
    int value;
    value = src[offset + 0] & 0xFF;
    value |= ((long) (src[offset + 1] & 0xFF) << 8);
    value |= ((long) (src[offset + 2] & 0xFF) << 16);
    value |= ((long) (src[offset + 3] & 0xFF) << 24);
    return Float.intBitsToFloat(value);
}

/**
 * byte轉(zhuǎn)double
 * @Title: byteToDouble
 *
 * @param: @param src 源數(shù)組
 * @param: @param offset 起始偏移量
 * @return: double
 */
public static double byteToDouble(byte[] src, int offset) {
    long value = 0;
    for (int i = 0; i < 8; i++) {
        value |= ((long) (src[offset + i] & 0xff)) << (8 * i);
    }
    return Double.longBitsToDouble(value);
}


public static void main(String[] args){
    File file = new File("C:\\Users\\Administrator\\Desktop\\test.txt"); // 要讀取的文件名
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file), "GBK"))) {
        String line;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    try{
        String str = "hello";
        byte[] bytes = str.getBytes("GBK"); // 將字符串轉(zhuǎn)換為字節(jié)數(shù)組
        String newStr = new String(bytes, "GBK"); // 將字節(jié)數(shù)組轉(zhuǎn)換為字符串
        System.out.println("源字符串："+str);
    }catch (Exception e){
        e.printStackTrace();
    }

}

}
注：其中c語言二進制字節(jié)碼int、double、float型通過位運算皆可；
而string類型轉(zhuǎn)換的時候存在亂碼，此時我是通過通配符替換掉亂碼的，就是除了中文、數(shù)字、特殊字符一律替換為空；
另外還有一個問題，就是netty的channel循環(huán)接收時，上一輪的字節(jié)數(shù)的最后不是字符的最后一位，這樣下一輪的開頭其實是一個字符剩下的部分，這時拼接轉(zhuǎn)寫也會出現(xiàn)為空的情況，這時java小端字節(jié)碼編碼方式造成的，只要規(guī)避即可。文章來源地址http://www.zghlxwxcb.cn/news/detail-831142.html

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