Netty拆包粘包

超、凢脫俗 2022-11-15 11:41 172阅读 0赞

# **拆包** #

拆包是指netty传输数据时候，会把一条信息，拆成几部分。比如："hello "拆成"he" 和 "llo"等，

# 粘包 #

粘包是指将多条信息连在一起 比如发送“hello”和"123"，而受到的是 "hello123"

解决方案：

1.  消息定长，比如固定传100字符，不够的用空格补充
2.  在尾部添加特殊字符
3.  发送信息是发送信息长度

下面我们来看一下定长怎么用

客户端

@Data
    public class MyMessageProtocol {
    
        //定义一次发送包体长度
        private int len;
        //一次发送包体内容
        private byte[] content;
    }
    
    public class NettyClientHandler extends SimpleChannelInboundHandler<MyMessageProtocol> {
        /**
         * 当客户端连接服务器完成就会触发该方法
         *
         * @param ctx
         * @throws Exception
         */
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            for(int i = 0; i< 10; i++) {
                String msg = "检测拆包";
                //创建协议包对象
                MyMessageProtocol messageProtocol = new MyMessageProtocol();
                messageProtocol.setLen(msg.getBytes(CharsetUtil.UTF_8).length);
                messageProtocol.setContent(msg.getBytes(CharsetUtil.UTF_8));
                ctx.writeAndFlush(messageProtocol);
            }
        }
    }
    
    public class PackMessageEncoder extends MessageToByteEncoder<MyMessageProtocol> {
        @Override
        protected void encode(ChannelHandlerContext ctx, MyMessageProtocol msg, ByteBuf out) throws Exception {
            System.out.println("MyMessageEncoder encode 方法被调用");
            out.writeInt(msg.getLen());
            out.writeInt(msg.getLen());
            out.writeBytes(msg.getContent());
        }
    }

服务端

public class PackNettyServerHandler extends SimpleChannelInboundHandler<MyMessageProtocol> {
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, MyMessageProtocol msg) throws Exception {
            System.out.println("====服务端接收到消息如下====");
            System.out.println("长度=" + msg.getLen());
            System.out.println("内容=" + new String(msg.getContent(), CharsetUtil.UTF_8));
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }
    
    public class PackMessageDecoder extends ByteToMessageDecoder {
    
        int length = 0;
    
        @Override
        protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
            //int类型长度4
            if(in.readableBytes() >= 4) {
                //获取到长度
                if (length == 0){
                    length = in.readInt();
                }
                if (in.readableBytes() < length) {
                    System.out.println("当前可读数据不够，继续等待。。");
                    return;
                }
                byte[] content = new byte[length];
                if (in.readableBytes() >= length){
                    in.readBytes(content);
    
                    //封装成MyMessageProtocol对象，传递到下一个handler业务处理
                    MyMessageProtocol messageProtocol = new MyMessageProtocol();
                    messageProtocol.setLen(length);
                    messageProtocol.setContent(content);
                    //交给下个handler处理
                    out.add(messageProtocol);
                }
                length = 0;
            }
        }
    }