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com.tangosol.util.aggregator
Class AbstractAggregator

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.aggregator.AbstractAggregator

All Implemented Interfaces:

ExternalizableLite, PortableObject, InvocableMap.EntryAggregator, InvocableMap.ParallelAwareAggregator, Serializable

Direct Known Subclasses:

AbstractBigDecimalAggregator, AbstractComparableAggregator, AbstractDoubleAggregator, AbstractLongAggregator, DistinctValues, ReducerAggregator

public abstract class AbstractAggregator

extends ExternalizableHelper

implements InvocableMap.ParallelAwareAggregator, ExternalizableLite, PortableObject

Abstract base class implementation of InvocableMap.EntryAggregator that supports parallel aggregation.

Since:

Coherence 3.1

Author:

cp/gg/jh 2005.07.19

Field Summary

protected boolean

m_fParallel Set to true if this aggregator realizes that it is going to be used in parallel.

Constructor Summary

AbstractAggregator()
Default constructor (necessary for the ExternalizableLite interface).

AbstractAggregator(String sMethod)
Construct an AbstractAggregator that will aggregate values extracted from a set of InvocableMap.Entry objects.

AbstractAggregator(ValueExtractor extractor)
Construct an AbstractAggregator that will aggregate values extracted from a set of InvocableMap.Entry objects.

Method Summary

Object	aggregate(Set setEntries) Process a set of InvocableMap.Entry objects in order to produce an aggregated result.
Object	aggregateResults(Collection collResults) Aggregate the results of the parallel aggregations.
boolean	equals(Object o) Compares this object with another object for equality.
protected abstract Object	finalizeResult(boolean fFinal) Obtain the result of the aggregation.
InvocableMap.EntryAggregator	getParallelAggregator() Get an aggregator that can take the place of this aggregator in situations in which the InvocableMap can aggregate in parallel.
ValueExtractor	getValueExtractor() Determine the ValueExtractor whose values this aggregator is aggregating.
int	hashCode() Returns a hash code value for this object.
protected abstract void	init(boolean fFinal) Initialize the aggregation result.
protected abstract void	process(Object o, boolean fFinal) Incorporate one aggregatable value into the result.
protected void	processEntry(InvocableMap.Entry entry) Incorporate one aggregatable entry into the result.
void	readExternal(DataInput in) Restore the contents of this object by loading the object's state from the passed DataInput object.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
String	toString() Provide a human-readable representation of this object.
void	writeExternal(DataOutput out) Save the contents of this object by storing the object's state into the passed DataOutput object.
void	writeExternal(PofWriter out) Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Methods inherited from class com.tangosol.util.BitHelper

countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString

Field Detail

m_fParallel

protected boolean m_fParallel

Set to true if this aggregator realizes that it is going to be used in parallel.

Constructor Detail

AbstractAggregator

public AbstractAggregator()

Default constructor (necessary for the ExternalizableLite interface).

AbstractAggregator

public AbstractAggregator(ValueExtractor extractor)

Construct an AbstractAggregator that will aggregate values extracted from a set of InvocableMap.Entry objects.

Parameters:

extractor - the extractor that provides values to aggregate

AbstractAggregator

public AbstractAggregator(String sMethod)

Construct an AbstractAggregator that will aggregate values extracted from a set of InvocableMap.Entry objects.

Parameters:

sMethod - the name of the method that could be invoked via reflection and that returns values to aggregate; this parameter can also be a dot-delimited sequence of method names which would result in an aggregator based on the ChainedExtractor that is based on an array of corresponding ReflectionExtractor objects

Method Detail

aggregate

public Object aggregate(Set setEntries)

Process a set of InvocableMap.Entry objects in order to produce an aggregated result.

Specified by:

aggregate in interface InvocableMap.EntryAggregator

Parameters:

setEntries - a Set of read-only InvocableMap.Entry objects to aggregate

Returns:

the aggregated result from processing the entries

processEntry

protected void processEntry(InvocableMap.Entry entry)

Incorporate one aggregatable entry into the result.

Parameters:

entry - the entry to incorporate into the aggregation result

getParallelAggregator

public InvocableMap.EntryAggregator getParallelAggregator()

Get an aggregator that can take the place of this aggregator in situations in which the InvocableMap can aggregate in parallel.

Specified by:

getParallelAggregator in interface InvocableMap.ParallelAwareAggregator

Returns:

the aggregator that will be run in parallel

aggregateResults

public Object aggregateResults(Collection collResults)

Aggregate the results of the parallel aggregations.

Specified by:

aggregateResults in interface InvocableMap.ParallelAwareAggregator

Parameters:

collResults - the parallel aggregation results

Returns:

the aggregation of the parallel aggregation results

getValueExtractor

public ValueExtractor getValueExtractor()

Determine the ValueExtractor whose values this aggregator is aggregating.

Returns:

the ValueExtractor used by this aggregator

init

protected abstract void init(boolean fFinal)

Initialize the aggregation result.

Parameters:

fFinal - true is passed if the aggregation process that is being initialized must produce a final aggregation result; this will only be false if a parallel approach is being used and the initial (partial) aggregation process is being initialized

process

protected abstract void process(Object o,
                                boolean fFinal)

Incorporate one aggregatable value into the result. <p/> If the fFinal parameter is true, the given object is a partial result (returned by an individual parallel aggregator) that should be incorporated into the final result; otherwise, the object is a value extracted from an InvocableMap.Entry.

Parameters:

o - the value to incorporate into the aggregated result

fFinal - true to indicate that the given object is a partial result returned by a parallel aggregator

finalizeResult

protected abstract Object finalizeResult(boolean fFinal)

Obtain the result of the aggregation. <p/> If the fFinal parameter is true, the returned object must be the final result of the aggregation; otherwise, the returned object will be treated as a partial result that should be incorporated into the final result.

Parameters:

fFinal - true to indicate that the final result of the aggregation process should be returned; this will only be false if a parallel approach is being used

Returns:

the result of the aggregation process

toString

public String toString()

Provide a human-readable representation of this object.

Returns:

a String whose contents represent the value of this object

hashCode

public int hashCode()

Returns a hash code value for this object.

Returns:

a hash code value for this object

equals

public boolean equals(Object o)

Compares this object with another object for equality.

Parameters:

o - an object reference or null

Returns:

true iff the passed object reference is of the same class and has the same state as this object

readExternal

public void readExternal(DataInput in)
                  throws IOException

Restore the contents of this object by loading the object's state from the passed DataInput object.

Specified by:

readExternal in interface ExternalizableLite

Parameters:

in - the DataInput stream to read data from in order to restore the state of this object

Throws:

IOException - if an I/O exception occurs

NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(DataOutput out)
                   throws IOException

Save the contents of this object by storing the object's state into the passed DataOutput object.

Specified by:

writeExternal in interface ExternalizableLite

Parameters:

out - the DataOutput stream to write the state of this object to

Throws:

IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws IOException

Restore the contents of a user type instance by reading its state using the specified PofReader object.

Specified by:

readExternal in interface PortableObject

Parameters:

in - the PofReader from which to read the object's state

Throws:

IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws IOException

Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Specified by:

writeExternal in interface PortableObject

Parameters:

out - the PofWriter to which to write the object's state

Throws:

IOException - if an I/O error occurs

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