okhttp - 两次读取 OKIO 流

Question

我正在使用 OKHTTP 进行网络连接，目前从 response.charStream() 获取 charStream，然后将其传递给 GSON 进行解析。解析和膨胀后，我再次对模型进行放气以使用流保存到磁盘。从 networkReader 到 Model 再到 DiskWriter 似乎是额外的工作。OKIO 是否可以改为从 networkReader 到 JSONParser(reader) 以及 networkReader 到 DiskWriter(reader)。基本上我希望能够从网络流中读取两次。

Answer 1

您可以使用 a MirroredSource（取自此 gist）。

public class MirroredSource {

    private final Buffer buffer = new Buffer();
    private final Source source;
    private final AtomicBoolean sourceExhausted = new AtomicBoolean();

    public MirroredSource(final Source source) {
        this.source = source;
    }

    public Source original() {
        return new okio.Source() {

            @Override
            public long read(final Buffer sink, final long byteCount) throws IOException {
                final long bytesRead = source.read(sink, byteCount);
                if (bytesRead > 0) {
                    synchronized (buffer) {
                        sink.copyTo(buffer, sink.size() - bytesRead, bytesRead);
                        // Notfiy the mirror to continue
                        buffer.notify();
                    }
                } else {
                    sourceExhausted.set(true);
                }
                return bytesRead;
            }

            @Override
            public Timeout timeout() {
                return source.timeout();
            }

            @Override
            public void close() throws IOException {
                source.close();
                sourceExhausted.set(true);
                synchronized (buffer) {
                    buffer.notify();
                }
            }
        };
    }

    public Source mirror() {
        return new okio.Source() {

            @Override
            public long read(final Buffer sink, final long byteCount) throws IOException {
                synchronized (buffer) {
                    while (!sourceExhausted.get()) {
                        // only need to synchronise on reads when the source is not exhausted.

                        if (buffer.request(byteCount)) {
                            return buffer.read(sink, byteCount);
                        } else {
                            try {
                                buffer.wait();
                            } catch (final InterruptedException e) {
                                //No op
                            }
                        }
                    }
                }
                return buffer.read(sink, byteCount);
            }

            @Override
            public Timeout timeout() {
                return new Timeout();
            }

            @Override
            public void close() throws IOException { /* not used */ }
        };
    }
}

用法如下所示：

MirroredSource mirroredSource = new MirroredSource(response.body().source()); //Or however you're getting your original source
Source originalSource = mirroredSource.original();
Source secondSource = mirroredSource.mirror();
doParsing(originalSource);
writeToDisk(secondSource);
originalSource.close();

如果你想要更健壮的东西，你可以Relay从 OkHttp 重新调整用途。