什么样代码是简洁易懂, 这很难有个统一的标准, 因为它很大程度上决定于所在团队的编写风格(往往偏向于核心程序员).
正因如此, 本文仅仅呈现一下DSL的编码风格, 若你喜欢, 不妨在自己的实践中也试试; 不欣赏者, 只当浮云飘过吧
有如下java代码片段:
| 以下是代码片段： public class Subscriber { private long skip; private final Channel channel; public Subscriber(final Channel channel, final long skip) { this.channel = channel; this.skip = skip; } public void receive(final ChannelBuffer buffer) throws Exception { if (buffer == null) { channel.write(new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK)); channel.close(); return; } if (skip == 0) { channel.write(buffer); return; } if (buffer.readableBytes() <= skip) { skip = skip - buffer.readableBytes(); return; } buffer.skipBytes((int) skip); channel.write(buffer); skip = 0; } } |
代码并不多, 看上去也还算简洁, 只是需要细细琢磨一下才能明白编写者的意图.
为了达到”显意”(代码尽可能直接表露业务含义, 而非执行步骤), 让我们重构一下:
| 以下是代码片段： public void receive(final ChannelBuffer buffer) throws Exception { if (isTail(buffer)) { sendOkResponseTo(channel); return; } if (skip == 0) { send(buffer, channel); return; } if (buffer.readableBytes() <= skip) { skip = skip - buffer.readableBytes(); return; } buffer.skipBytes((int) skip); send(buffer,channel); skip = 0; } static void send(final ChannelBuffer buffer, Channel channel) { channel.write(buffer); } static void sendOkResponseTo(Channel channel) { channel.write(new DefaultHttpResponse(HTTP_1_1, OK)); // import static constants channel.close(); } static boolean isTail(final ChannelBuffer buffer) { return buffer == null; } |
似乎好了点, 至少能够一看出来的是:
- 若buffer到达结尾, 需要向channel发送OK的应答, 并关闭channel;
- 此外需要根据skip和buffer.readableBytes的大小关系, 决定要不要向channel发送buffer
有两点小不足的是:
- skip和buffer.readableBytes的大小关系, 如何处理不明了;
- if - return 看着不够简洁.
再重构一下:
| 以下是代码片段： public void receive(final ChannelBuffer buffer) throws Exception { if (isTail(buffer) && thenSendOkResponseAndClose(channel)) return; if (buffer.readableBytes() <= skip && thenSkip(buffer)) return; if (skip > 0) skipPartOf(buffer); send(buffer); skip = 0; } boolean thenSkip(final ChannelBuffer buffer) { skip = skip - buffer.readableBytes(); return true; } void send(final ChannelBuffer buffer) { channel.write(buffer); } void skipPartOf(final ChannelBuffer buffer) { buffer.skipBytes((int) skip); } static boolean isTail(final ChannelBuffer buffer) { return buffer == null; } static boolean thenSendOkResponseAndClose(final Channel channel) { channel.write(build(OK).response()); channel.close(); return true; } |
尽管代码行数上比最初的版本有了少许增加, 但核心方法receive的意图却变的更为明显了.