Netty拆包粘包

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：

消息定长，比如固定传100字符，不够的用空格补充
在尾部添加特殊字符
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;
        }
    }
}