hadoop示例代碼

• 序列化和反序列化

IntWritable writable = new IntWritable();
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        DataOutputStream dataOutputStream = new DataOutputStream(byteArrayOutputStream);
        writable.write(dataOutputStream);
        dataOutputStream.close();
        byte[] bytes = byteArrayOutputStream.toByteArray();
        System.out.println(StringUtils.byteToHexString(bytes));
        //解序列化
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
        DataInputStream input = new DataInputStream(byteArrayInputStream);
        IntWritable intWritable = new IntWritable();
        intWritable.readFields(input);
        input.close();
        System.out.println(intWritable);
           

• writable對象的比較

IntWritable int1 = new IntWritable();
        IntWritable int2 = new IntWritable();
        RawComparator<IntWritable> comparator = WritableComparator.get(IntWritable.class);
        System.out.println(comparator.compare(int1,int2));
        //也可以直接比較位元組流，不需要反序列化，問題是怎麼定位這個位元組流呢
        System.out.println(comparator.compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2));