Package com.tangosol.util.aggregator

Class AbstractAggregator<K,V,T,E,R>

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.aggregator.AbstractAggregator<K,V,T,E,R>
Type Parameters:
K - the type of the Map entry key
V - the type of the Map entry value
T - the type of the value to extract from
E - the type of the extracted value to aggregate
R - the type of the aggregation result
All Implemented Interfaces:
ExternalizableLite, PortableObject, InvocableMap.EntryAggregator<K,V,R>, InvocableMap.StreamingAggregator<K,V,Object,R>, Serializable, Cloneable
Direct Known Subclasses:
AbstractBigDecimalAggregator, AbstractComparableAggregator, AbstractDoubleAggregator, AbstractLongAggregator, DistinctValues, ReducerAggregator
public abstract class AbstractAggregator<K,V,T,E,R> extends ExternalizableHelper implements InvocableMap.StreamingAggregator<K,V,Object,R>, ExternalizableLite, PortableObject, Cloneable
Abstract base class implementation of InvocableMap.EntryAggregator that supports streaming aggregation.
Since:
Coherence 3.1
Author:
cp/gg/jh 2005.07.19
See Also:

  • Field Details

    • m_fParallel

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

  • Constructor Details

    • AbstractAggregator

      public AbstractAggregator()
      Deserialization constructor.

    • AbstractAggregator

      public AbstractAggregator(ValueExtractor<? super T,? extends E> 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 Details

    • supply

      public InvocableMap.StreamingAggregator<K,V,Object,R> supply()
      Description copied from interface: InvocableMap.StreamingAggregator
      Create a new instance of this aggregator.
      Specified by:
      supply in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Returns:
      a StreamAggregator

    • accumulate

      public boolean accumulate(Streamer<? extends InvocableMap.Entry<? extends K,? extends V>> streamer)
      Description copied from interface: InvocableMap.StreamingAggregator
      Accumulate multiple entries into the result.

      Important note: The default implementation of this method provides necessary logic for aggregation short-circuiting and should rarely (if ever) be overridden by the custom aggregator implementation.

      Specified by:
      accumulate in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Parameters:
      streamer - a Streamer that can be used to iterate over entries to add
      Returns:
      true to continue the aggregation, and false to signal to the caller that the result is ready and the aggregation can be short-circuited

    • accumulate

      public boolean accumulate(InvocableMap.Entry<? extends K,? extends V> entry)
      Description copied from interface: InvocableMap.StreamingAggregator
      Accumulate one entry into the result.
      Specified by:
      accumulate in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Parameters:
      entry - the entry to accumulate into the aggregation result
      Returns:
      true to continue the aggregation, and false to signal to the caller that the result is ready and the aggregation can be short-circuited

    • combine

      public boolean combine(Object partialResult)
      Description copied from interface: InvocableMap.StreamingAggregator
      Merge another partial result into the result.
      Specified by:
      combine in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Parameters:
      partialResult - the partial result to merge
      Returns:
      true to continue the aggregation, and false to signal to the caller that the result is ready and the aggregation can be short-circuited

    • getPartialResult

      public Object getPartialResult()
      Description copied from interface: InvocableMap.StreamingAggregator
      Return the partial result of the aggregation.
      Specified by:
      getPartialResult in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Returns:
      the partial result of the aggregation

    • finalizeResult

      public R finalizeResult()
      Description copied from interface: InvocableMap.StreamingAggregator
      Return the final result of the aggregation.
      Specified by:
      finalizeResult in interface InvocableMap.StreamingAggregator<K,V,T,E>
      Returns:
      the final result of the aggregation

    • ensureInitialized

      protected void ensureInitialized(boolean fFinal)
      Ensure that this aggregator is initialized.
      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

    • processEntry

      protected void processEntry(InvocableMap.Entry<? extends K,? extends V> entry)
      Incorporate one aggregatable entry into the result.
      Parameters:
      entry - the entry to incorporate into the aggregation result

    • getValueExtractor

      public ValueExtractor<? super T,? extends E> 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.

      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.

      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.
      Overrides:
      toString in class Object
      Returns:
      a String whose contents represent the value of this object

    • hashCode

      public int hashCode()
      Returns a hash code value for this object.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object

    • equals

      public boolean equals(Object o)
      Compares this object with another object for equality.
      Overrides:
      equals in class Object
      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
      Description copied from interface: ExternalizableLite
      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

    • writeExternal

      public void writeExternal(DataOutput out) throws IOException
      Description copied from interface: ExternalizableLite
      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
      Description copied from interface: PortableObject
      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
      Description copied from interface: PortableObject
      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