Nio中Buffer的Scattering和Gathering

* Scattering:将数据写入到buffer时，可以采用buffer数组，依次写入
* Gathering:从buffer读取数据时，可以采用buffer数组，依次读取

示例代码

public static void main(String[] args) throws IOException {
    //使用serversocketchannel和socketchannel，客户端就用telnet连接
    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
    InetSocketAddress inetSocketAddress = new InetSocketAddress(8000);
    //绑定接口到socket,并启动
    serverSocketChannel.socket().bind(inetSocketAddress);
    ByteBuffer[] byteBuffers = new ByteBuffer[2];
    byteBuffers[0] = ByteBuffer.allocate(5);
    byteBuffers[1] = ByteBuffer.allocate(3);
    //等待客户端连接（telnet）
    SocketChannel socketChannel = serverSocketChannel.accept();
    int messageLength = 8;//假定从客户端接受8个字节
    while(true){
        int byteRead = 0;
        while(byteRead< messageLength){
            long r =  socketChannel.read(byteBuffers);
            byteRead +=r;
            System.out.println("byteRead"+byteRead);
            //使用流打印，看当前buffer的postion和limit
            Arrays.asList(byteBuffers).stream().map(buffer ->"postion=" +buffer.position()+",limit="+buffer.limit()).forEach(System.out::println);
        }

        //将所有的buffer反转
        Arrays.asList(byteBuffers).forEach(byteBuffer -> byteBuffer.flip());
        //将数据读出显示到客户端
        long byteWirte = 0;
        while(byteWirte<messageLength){
            long l = socketChannel.write(byteBuffers);
            byteWirte+=l;
        }
        //将所有的buffer 运行claer
        Arrays.asList(byteBuffers).forEach(byteBuffer -> byteBuffer.clear());
        System.out.println("byteRead:"+byteWirte+"byteWrite"+byteWirte+"messagelength"+messageLength);
    }
}

当使用telnet发送9个byte的数组时

当使用telnet再次发送6个byte的数组时

再次连续发送两次一个byte

 由此可以看出Scattering的意思就像buffer数组像水杯一样，将数据（水）倒入数组的第一个buffer，满了的话，就向第二个buffer接着倒，一直到buffer数组都倒满。

而Gathering就是在读取的时候将按顺序，数组里的buffer一个一个的倒出来，拼成一句完整的信息