Question

我想通过将它们打包到一个字节数组中来发送到我们的消息队列中的一堆键和值。我将创建所有键和值的一个字节数组，该数组应始终小于50K，然后发送到我们的消息队列。我有标题，然后是数据。

数据包类：

public final class Packet implements Closeable {
  private static final int MAX_SIZE = 50000;
  private static final int HEADER_SIZE = 36;

  private final byte dataCenter;
  private final byte recordVersion;
  private final long address;
  private final long addressFrom;
  private final long addressOrigin;
  private final byte recordsPartition;
  private final byte replicated;
  private final ByteBuffer itemBuffer = ByteBuffer.allocate(MAX_SIZE);
  private int pendingItems = 0;

  public Packet(final RecordPartition recordPartition) {
    this.recordsPartition = (byte) recordPartition.getPartition();
    this.dataCenter = Utils.LOCATION.getDatacenter();
    this.recordVersion = 1;
    this.replicated = 0;
    final long packedAddress = new Data().packAddress();
    this.address = packedAddress;
    this.addressFrom = 0L;
    this.addressOrigin = packedAddress;
  }

  private void addHeader(final ByteBuffer buffer, final int items) {
    buffer.put(dataCenter).put(recordVersion).putInt(items).putInt(buffer.capacity())
        .putLong(address).putLong(addressFrom).putLong(addressOrigin).put(recordsPartition)
        .put(replicated);
  }

  private void sendData() {
    if (itemBuffer.position() == 0) {
      // no data to be sent
      return;
    }
    final ByteBuffer buffer = ByteBuffer.allocate(MAX_SIZE);
    addHeader(buffer, pendingItems);
    // below line throws "BufferOverflowException"
    buffer.put(itemBuffer);
    SendRecord.getInstance().sendToQueueAsync(address, buffer.array());
    itemBuffer.clear();
    pendingItems = 0;
  }

  public void addAndSendJunked(final byte[] key, final byte[] data) {
    if (key.length > 255) {
      return;
    }
    final byte keyLength = (byte) key.length;
    final byte dataLength = (byte) data.length;

    final int additionalSize = dataLength + keyLength + 1 + 1 + 8 + 2;
    final int newSize = itemBuffer.position() + additionalSize;
    if (newSize >= (MAX_SIZE - HEADER_SIZE)) {
      sendData();
    }
    if (additionalSize > (MAX_SIZE - HEADER_SIZE)) {
      throw new AppConfigurationException("Size of single item exceeds maximum size");
    }

    final ByteBuffer dataBuffer = ByteBuffer.wrap(data);
    final long timestamp = dataLength > 10 ? dataBuffer.getLong(2) : System.currentTimeMillis();
    // data layout
    itemBuffer.put((byte) 0).put(keyLength).put(key).putLong(timestamp).putShort(dataLength)
        .put(data);
    pendingItems++;
  }

  @Override
  public void close() {
    if (pendingItems > 0) {
      sendData();
    }
  }
}

在上面的代码中，我在java.nio.BufferOverflowException方法的buffer.put(itemBuffer);处获得sendData。我无法理解为什么我会得到这个例外以及如何解决它。

以下是我调用此代码的方式：

Packet packet = new Packet(partition);
packet.addAndSendJunked("hello".getBytes(StandardCharsets.UTF_8), StringUtils.EMPTY.getBytes(StandardCharsets.UTF_8));
packet.close();

Answer 1

显然itemBuffer加上已放入buffer的标题长度超过buffer.capacity()，即MAX_SIZE。

Ergo addHeader()或其他任何创建itemBuffer的错误，或者MAX_SIZE太小。

NB

SendRecord.getInstance().sendToQueueAsync(address, buffer.array());

在这里，您将MAX_SIZE字节的整个buffer入队，即使您可能没有将MAX_SIZE字节放入其中。最好将buffer本身传递给此方法，并避免代码中的不断包装。

发送特定大小的数据时发生BufferOverflowException

1 个答案: