com.aliyun.odps.io

Interface Writable

All Known Subinterfaces:

InputBlobWritable, OutputBlobWritable, WritableComparable<T>

All Known Implementing Classes:

AbstractDatetimeWritable, AbstractMapWritable, ArrayWritable, BigDecimalWritable, BitMapWritable, BooleanWritable, BytesWritable, ByteWritable, CharWritable, Configuration, Counter, CounterGroup, Counters, DatetimeWritable, DateWritable, DoubleWritable, FloatWritable, IntervalDayTimeWritable, IntervalYearMonthWritable, IntWritable, LongWritable, MapWritable, NullWritable, ShortWritable, SortedMapWritable, StructWritable, Text, TimestampWritable, Tuple, VarcharWritable

public interface Writable

Writable 定义了基于 DataInput 和 DataOutput 的序列化和反序列化接口.

com.aliyun.odps.Record 列值要求实现 Writable 接口。

com.aliyun.odps.mapreduce.Mapper 输出的 Key/Value 要求实现 Writable 接口。

用户可以实现 Writable 接口，代码示例：

 public class MyWritable implements Writable {
   // Some data
   private int counter;
   private long timestamp;

   public void write(DataOutput out) throws IOException {
     out.writeInt(counter);
     out.writeLong(timestamp);
   }

   public void readFields(DataInput in) throws IOException {
     counter = in.readInt();
     timestamp = in.readLong();
   }

   public static MyWritable read(DataInput in) throws IOException {
     MyWritable w = new MyWritable();
     w.readFields(in);
     return w;
   }
 }
 

Method Summary

Modifier and Type	Method and Description
void	readFields(DataInput in) 从指定的 DataInput in 反序列化.
void	write(DataOutput out) 序列化到指定的 DataOutput out.

Method Detail

write

void write(DataOutput out)
    throws IOException

序列化到指定的 DataOutput out.

Parameters:

out -

Throws:

IOException

readFields

void readFields(DataInput in)
         throws IOException

从指定的 DataInput in 反序列化.

Parameters:

in -

Throws:

IOException