org.apache.hadoop.mapred.lib.aggregate

类 UserDefinedValueAggregatorDescriptor

java.lang.Object

org.apache.hadoop.mapred.lib.aggregate.UserDefinedValueAggregatorDescriptor

所有已实现的接口:

ValueAggregatorDescriptor

public class UserDefinedValueAggregatorDescriptor
extends Object
implements ValueAggregatorDescriptor

This class implements a wrapper for a user defined value aggregator descriptor. It servs two functions: One is to create an object of ValueAggregatorDescriptor from the name of a user defined class that may be dynamically loaded. The other is to deligate inviokations of generateKeyValPairs function to the created object.

字段概要

从接口继承的字段 org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorDescriptor

ONE, TYPE_SEPARATOR

构造器概要

构造器

构造器和说明
UserDefinedValueAggregatorDescriptor(String className, JobConf job)

方法概要

方法

限定符和类型	方法和说明
void	configure(JobConf job) Do nothing.
static Object	createInstance(String className) Create an instance of the given class
ArrayList<Map.Entry<Text,Text>>	generateKeyValPairs(Object key, Object val) Generate a list of aggregation-id/value pairs for the given key/value pairs by delegating the invocation to the real object.
String	toString()

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

构造器详细资料

UserDefinedValueAggregatorDescriptor

public UserDefinedValueAggregatorDescriptor(String className,
                                    JobConf job)

参数:

className - the class name of the user defined descriptor class

job - a configure object used for decriptor configuration

方法详细资料

createInstance

public static Object createInstance(String className)

Create an instance of the given class

参数:

className - the name of the class

返回:

a dynamically created instance of the given class

generateKeyValPairs

public ArrayList<Map.Entry<Text,Text>> generateKeyValPairs(Object key,
                                                  Object val)

Generate a list of aggregation-id/value pairs for the given key/value pairs by delegating the invocation to the real object.

指定者:

generateKeyValPairs 在接口中 ValueAggregatorDescriptor

参数:

key - input key

val - input value

返回:

a list of aggregation id/value pairs. An aggregation id encodes an aggregation type which is used to guide the way to aggregate the value in the reduce/combiner phrase of an Aggregate based job.

toString

public String toString()

覆盖:

toString 在类中 Object

返回:

the string representation of this object.

configure

public void configure(JobConf job)

Do nothing.

指定者:

configure 在接口中 ValueAggregatorDescriptor

参数:

job - a JobConf object that may contain the information that can be used to configure the object.