java - 如何将字节数组写入和读取到 DataInput 和 DataOutput Stream

Question

Hbase 充当我的 Map reduce 作业的源和接收器。我已经编写了名为(vector writable)的自定义可写类，它有两个字段。

private DoubleVector vector; // It is a Double Array
private byte[] rowKey;       // The row key of the Hbase 

我的映射器将它作为它的值发出，因此我在我的 vectorWritable 类中实现了写入和读取方法

  @Override
   public final void write(DataOutput out) throws IOException {
   writeVectorCluster(this.vector, this.rowKey, out);       
   }

   @Override
   public final void readFields(DataInput in) throws IOException {
   this.vector = readVector(in);
   this.rowKey = readRowKey(in);
   } 

public static void writeVectorCluster(DoubleVector vector, byte[] rowkey, DataOutput out)
            throws IOException {
        out.writeInt(vector.getLength());
            for (int i = 0; i < vector.getDimension(); i++) {
                out.writeDouble(vector.get(i));
            }
            int length = rowkey.length;
            out.writeInt(length);

           //Is this the right way ?
            out.write(rowkey);
        }


public static DoubleVector readVector(DataInput in) throws IOException {
        int length = in.readInt();
        DoubleVector vector = null;
            vector = new DenseDoubleVector(length);
            for (int i = 0; i < length; i++) {
                vector.set(i, in.readDouble());
            }
        return vector;
    }

   @SuppressWarnings("null")
    public static byte[] readRowKey(DataInput in) throws IOException {
        int length = in.readInt();
        byte [] test = null;
            for (int i = 0; i < length; i++) {
                // getting null pointer exception here
                test[i] = in.readByte();
            }
        return test;
    }

当我尝试从输入流中读取 rowKey 时，出现 NullPointerException。 readVector 方法工作正常，我得到了正确的值。

如何在 DataInput 流中写入字节数组，以便我可以在我的输出流中检索它

更新:已解决 这是我的 rowKey 方法的更新，效果很好。谢谢@Perception

public static byte[] readRowKey(DataInput in) throws IOException {  
        int length = in.readInt();
        byte[] theBytes = new byte[length];
        in.readFully(theBytes); 
        return theBytes;
    }

Answer 1

你没有初始化你的字节数组:

byte [] test = null;

应该是:

byte [] test = new byte[length];