private Code code;  //状态代码

  private Content content;  //响应正文

  private boolean headersOnly;  //表示HTTP响应中是否仅包含响应头

  private ByteBuffer headerBuffer = null;  //响应头

  public Response(Code rc, Content c) {

    this(rc, c, null);

  }

  public Response(Code rc, Content c, Request.Action head) {

    code = rc;

    content = c;

    headersOnly = (head == Request.Action.HEAD);

  }

  private static String CRLF = "\r\n";

  private static Charset responseCharset = Charset.forName("GBK");

  /* 创建响应头的内容，把它存放到一个ByteBuffer中 */

  private ByteBuffer headers() {

    CharBuffer cb = CharBuffer.allocate(1024);

    for (;;) {

        try {

            cb.put("HTTP/1.1 ").put(code.toString()).put(CRLF);

            cb.put("Server: nio/1.1").put(CRLF);

            cb.put("Content-type: ").put(content.type()).put(CRLF);

            cb.put("Content-length: ")

                .put(Long.toString(content.length())).put(CRLF);

            cb.put(CRLF);

            break;

        } catch (BufferOverflowException x) {

            assert(cb.capacity() < (1 << 16));

            cb = CharBuffer.allocate(cb.capacity() * 2);

            continue;

        }

    }

    cb.flip();

    return responseCharset.encode(cb);  //编码

  }

  /* 准备HTTP响应中的正文以及响应头的内容 */

  public void prepare() throws IOException {

    content.prepare();

    headerBuffer= headers();

  }

  /* 发送HTTP响应，如果全部发送完毕，返回false，否则返回true */

  public boolean send(ChannelIO cio) throws IOException {

    if (headerBuffer == null)

        throw new IllegalStateException();