Netty java从ByteBuf获取数据

Question

如何ByteBuf在下面的代码中有效地获取字节数组？我需要获取数组然后序列化它.

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

public class ServerHandler extends  ChannelInboundHandlerAdapter {
     @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) {
         System.out.println("Message receive");
         ByteBuf buff = (ByteBuf) msg;
             // There is I need get bytes from buff and make serialization
         byte[] bytes = BuffConvertor.GetBytes(buff);
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { 
            // Close the connection when an exception is raised.
            cause.printStackTrace();
            ctx.close();
        }

}

Answer 1

ByteBuf buf = ...
byte[] bytes = new byte[buf.readableBytes()];
buf.readBytes(bytes);

如果您不希望readerIndex更改:

ByteBuf buf = ...
byte[] bytes = new byte[buf.readableBytes()];
int readerIndex = buf.readerIndex();
buf.getBytes(readerIndex, bytes);

如果要最小化内存副本,可以使用它的后备数组(ByteBuf如果可用):

ByteBuf buf = ...
byte[] bytes;
int offset;
int length = buf.readableBytes();

if (buf.hasArray()) {
    bytes = buf.array();
    offset = buf.arrayOffset();
} else {
    bytes = new byte[length];
    buf.getBytes(buf.readerIndex(), bytes);
    offset = 0;
}

请注意,您不能简单地使用buf.array(),因为:

• 并非所有人ByteBuf都有支持阵列.一些是堆外缓冲区(即直接内存)
• 即使a ByteBuf具有后备数组(即buf.hasArray()返回true),以下情况也不一定正确,因为缓冲区可能是其他缓冲区或池缓冲区的片段:
  • buf.array()[0] == buf.getByte(0)
  • buf.array().length == buf.capacity()

Answer 2

另一种选择是ByteBufUtil.getBytes(ByteBuf buf, int start, int length, boolean copy)

参见ByteBufUtil