com.aliyun.odps.io

Class TupleReaderWriter

java.lang.Object

com.aliyun.odps.io.TupleReaderWriter

public class TupleReaderWriter
extends Object

TupleReaderWriter 提供 Tuple 的序列化和反序列化方法.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TupleReaderWriter.TupleRawComparator Tuple 对象的 WritableComparator 自然顺序实现（升序）.

Constructor Summary

Constructors

Constructor and Description
TupleReaderWriter()

Method Summary

Modifier and Type	Method and Description
static int	compare(Writable o1, Writable o2) /** Compare two objects to each other.
static int	compare(Writable o1, Writable o2, byte dt1, byte dt2) Same as #compare(Object, Object), but does not use reflection to determine the type of passed in objects, relying instead on the caller to provide the appropriate values, as determined by findType(Object).
static void	readTuple(DataInput in, Tuple t) 从指定的输入流反序列化至指定的Tuple对象
static void	writeTuple(DataOutput out, Tuple t) 将指定的Tuple对象序列化至指定的输出流中

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TupleReaderWriter

public TupleReaderWriter()

Method Detail

compare

public static int compare(Writable o1,
                          Writable o2)

/** Compare two objects to each other. This function is necessary because there's no super class that implements compareTo. This function provides an (arbitrary) ordering of objects of different types as follows: NULL < BOOLEAN < BYTE < INTEGER < LONG < FLOAT < DOUBLE * < BYTEARRAY < STRING < MAP < TUPLE < BAG. No other functions should implement this cross object logic. They should call this function for it instead.

Parameters:

o1 - First object

o2 - Second object

Returns:

-1 if o1 is less, 0 if they are equal, 1 if o2 is less.

compare

public static int compare(Writable o1,
                          Writable o2,
                          byte dt1,
                          byte dt2)

Same as #compare(Object, Object), but does not use reflection to determine the type of passed in objects, relying instead on the caller to provide the appropriate values, as determined by findType(Object). Use this version in cases where multiple objects of the same type have to be repeatedly compared.

Parameters:

o1 - first object

o2 - second object

dt1 - type, as byte value, of o1

dt2 - type, as byte value, of o2

Returns:

-1 if o1 is < o2, 0 if they are equal, 1 if o1 > o2

readTuple

public static void readTuple(DataInput in,
                             Tuple t)
                      throws IOException

从指定的输入流反序列化至指定的Tuple对象

Parameters:

in - 输入流，含有Tuple的field的字节

t - 反序列化后的Tuple对象

Throws:

IOException - 输入流中的字节不是某个Tuple序列化后的字节

writeTuple

public static void writeTuple(DataOutput out,
                              Tuple t)
                       throws IOException

将指定的Tuple对象序列化至指定的输出流中

Parameters:

out - Tuple对象要写入的输出流

t - 待写出的Tuple对象

Throws:

IOException - 待序列化的Tuple对象在序列化其field对象出现异常