org.apache.hadoop.mapreduce.lib.aggregate

クラス UserDefinedValueAggregatorDescriptor

java.lang.Object

org.apache.hadoop.mapreduce.lib.aggregate.UserDefinedValueAggregatorDescriptor

すべての実装されたインタフェース:

ValueAggregatorDescriptor

直系の既知のサブクラス:

UserDefinedValueAggregatorDescriptor

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class UserDefinedValueAggregatorDescriptor
extends Object
implements ValueAggregatorDescriptor

This class implements a wrapper for a user defined value aggregator descriptor. It serves 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 delegate invocations of generateKeyValPairs function to the created object.

フィールドのサマリー

フィールド

修飾子とタイプ	フィールドと説明
protected ValueAggregatorDescriptor	theAggregatorDescriptor

インタフェースから継承されたフィールド org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor

ONE, TYPE_SEPARATOR

コンストラクタのサマリー

コンストラクタ

コンストラクタと説明
UserDefinedValueAggregatorDescriptor(String className, Configuration conf)

メソッドのサマリー

修飾子とタイプ	メソッドと説明
void	configure(Configuration conf) 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()

クラスから継承されたメソッド java.lang.Object

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

フィールドの詳細

theAggregatorDescriptor

protected ValueAggregatorDescriptor theAggregatorDescriptor

コンストラクタの詳細

UserDefinedValueAggregatorDescriptor

public UserDefinedValueAggregatorDescriptor(String className,
                                            Configuration conf)

パラメータ:

className - the class name of the user defined descriptor class

conf - a configure object used for decriptor configuration

メソッドの詳細

createInstance

public static Object createInstance(String className)

Create an instance of the given class

パラメータ:

className - the name of the class

戻り値:

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.

定義:

generateKeyValPairs インタフェース内 ValueAggregatorDescriptor

パラメータ:

key - input key

val - input value

戻り値:

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()

オーバーライド:

toString クラス内 Object

戻り値:

the string representation of this object.

configure

public void configure(Configuration conf)

Do nothing.

定義:

configure インタフェース内 ValueAggregatorDescriptor

パラメータ:

conf - a Configuration object that may contain the information that can be used to configure the object.