Java 类org.apache.commons.io.output.ProxyOutputStream 实例源码

/**
 * Returns an output stream for the requested file.
 *
 * After completing the write the contents must be committed using the {@link #commit(java.io.OutputStream)}
 * method and the stream must be released using the {@link #release()} method.
 *
 * Example usage:
 *
 * DataStore dataStore = new DataStore(...);
 * try (OutputStream os = dataStore.getOutputStream()) {
 *   os.write(..);
 *   dataStore.commit(os);
 * } catch (IOException e) {
 *   ...
 * } finally {
 *   dataStore.release();
 * }
 *
 * @return
 * @throws IOException
 */
public OutputStream getOutputStream() throws IOException {
  acquireLock();
  try {
    isClosed = false;
    forWrite = true;
    LOG.trace("Starts write '{}'", file);
    verifyAndRecover();
    if (Files.exists(file)) {
      Files.move(file, fileOld);
      LOG.trace("Starting write, move '{}' to '{}'", file, fileOld);
    }
    OutputStream os = new ProxyOutputStream(new FileOutputStream(fileTmp.toFile())) {
      @Override
      public void close() throws IOException {
        if (isClosed) {
          return;
        }
        try {
          super.close();
        } finally {
          isClosed = true;
          stream = null;
        }
        LOG.trace("Finishes write '{}'", file);
      }
    };
    stream = os;
    return os;
  } catch (Exception ex) {
    release();
    throw ex;
  }
}