怎样将字节数组写入和读出DataInput和DataOutput流？

Question

HBase可作为MapReduce作业的数据源和数据汇。我编写了自定义的Writable类，叫做“vector writable”，其中包含两个字段。

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

我的映射器将此作为其值发出，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，出现了一个NullPointerException。虽然readVector方法工作良好，我也得到了正确的值。

我应该如何将字节数组写入DataInput Stream，以便在我的Output streams中检索它

更新：已解决 这是我的rowKey方法的更新版，它工作得很好。感谢@Perception

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

- yesh

Answer 1

您没有初始化字节数组：

byte [] test = null;

应该是：

byte [] test = new byte[length];

- Perception