com.tangosol.util.aggregator
Class CompositeAggregator

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

All Implemented Interfaces:

ExternalizableLite, PortableObject, InvocableMap.EntryAggregator, Serializable

Direct Known Subclasses:

CompositeAggregator.Parallel

public class CompositeAggregator
extends ExternalizableHelper
implements InvocableMap.EntryAggregator, ExternalizableLite, PortableObject

CompositeAggregator provides an ability to execute a collection of aggregators against the same subset of the entries in an InvocableMap, resulting in a list of corresponding aggregation results. The size of the returned list will always be equal to the length of the aggregators' array.

Note: Unlike many other concrete EntryAggregator implementations that are constructed directly, instances of CompositeAggregator should only be created using the factory method createInstance.

Since:

Coherence 3.2

Author:

gg 2006.02.08

Nested Class Summary

static class

CompositeAggregator.Parallel Parallel implementation of the CompositeAggregator.

Field Summary

protected InvocableMap.EntryAggregator[]

m_aAggregator The underlying EntryAggregator array.

Constructor Summary

	CompositeAggregator() Default constructor (necessary for the ExternalizableLite interface).
protected	CompositeAggregator(InvocableMap.EntryAggregator[] aAggregator) Construct a CompositeAggregator based on a specified EntryAggregator array.

Method Summary

Object	aggregate(Set setEntries) Process a set of InvocableMap Entry objects using each of the underlying agregators in order to produce an array of aggregated results.
static CompositeAggregator	createInstance(InvocableMap.EntryAggregator[] aAggregator) Create an instance of CompositeAggregator based on a specified EntryAggregator array.
boolean	equals(Object o) Compare the CompositeAggregator with another object to determine equality.
InvocableMap.EntryAggregator[]	getAggregators() Obtain the EntryAggregator array.
int	hashCode() Determine a hash value for the MultiExtractor object according to the general Object.hashCode() contract.
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() Return a human-readable description for this ValueExtractor.
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, toBitString, toBitString, toBitString

Field Detail

m_aAggregator

protected InvocableMap.EntryAggregator[] m_aAggregator

The underlying EntryAggregator array.

Constructor Detail

CompositeAggregator

public CompositeAggregator()

Default constructor (necessary for the ExternalizableLite interface).

CompositeAggregator

protected CompositeAggregator(InvocableMap.EntryAggregator[] aAggregator)

Construct a CompositeAggregator based on a specified EntryAggregator array.

Parameters:

aAggregator - an array of EntryAggregator objects; may not be null

Method Detail

aggregate

public Object aggregate(Set setEntries)

Process a set of InvocableMap Entry objects using each of the underlying agregators in order to produce an array of aggregated results.

Specified by:

aggregate in interface InvocableMap.EntryAggregator

Parameters:

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

Returns:

a List of aggregated results from processing the entries by the corresponding underlying aggregators

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

getAggregators

public InvocableMap.EntryAggregator[] getAggregators()

Obtain the EntryAggregator array.

Returns:

the EntryAggregator array

equals

public boolean equals(Object o)

Compare the CompositeAggregator with another object to determine equality.

Returns:

true iff this CompositeAggregator and the passed object are equivalent

hashCode

public int hashCode()

Determine a hash value for the MultiExtractor object according to the general Object.hashCode() contract.

Returns:

an integer hash value for this ValueExtractor object

toString

public String toString()

Return a human-readable description for this ValueExtractor.

Returns:

a String description of the ValueExtractor

createInstance

public static CompositeAggregator createInstance(InvocableMap.EntryAggregator[] aAggregator)

Create an instance of CompositeAggregator based on a specified EntryAggregator array. If all the aggregators in the specified array are instances of ParallelAwareAggregator, then a parallel-aware instance of the CompositeAggregator will be created.
If at least one of the specified aggregator is not parallel-aware, then the resulting CompositeAggregator will not be parallel-aware and could be ill-suited for aggregations run against large partitioned caches.

Parameters:

aAggregator - an array of EntryAggregator objects; must contain not less than two aggregators