com.tangosol.util.extractor
Class MultiExtractor

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.util.extractor.AbstractExtractor
          com.tangosol.util.extractor.AbstractCompositeExtractor
              com.tangosol.util.extractor.MultiExtractor

All Implemented Interfaces:

ExternalizableLite, PortableObject, QueryMapComparator, ValueExtractor, Serializable, Comparator

public class MultiExtractor
extends AbstractCompositeExtractor

Composite ValueExtractor implementation based on an array of extractors. All extractors in the array are applied to the same target object and the result of the extraction is a List of extracted values.

Common scenarios for using the MultiExtractor involve the DistinctValues or GroupAggregator aggregators, that allow clients to collect all distinct combinations of a given set of attributes or collect and run additional aggregation against the corresponding groups of entries.

Since:

Coherence 3.2

Author:

gg 2006.02.08

Field Summary

Fields inherited from class com.tangosol.util.extractor.AbstractCompositeExtractor

m_aExtractor

Constructor Summary

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

MultiExtractor(String sNames)
Construct a MultiExtractor for a specified method name list.

MultiExtractor(ValueExtractor[] aExtractor)
Construct a MultiExtractor.

Method Summary

int	compareEntries(QueryMap.Entry entry1, QueryMap.Entry entry2) Compare two entries based on the rules specified by Comparator. If possible, use the extract method to optimize the value extraction process. This method is expected to be implemented by Comparator wrappers, such as ChainedComparator and InverseComparator, which simply pass on this invocation to the wrapped Comparator objects if they too implement this interface, or to invoke their default compare method passing the actual objects (not the extracted values) obtained from the extractor using the passed entries. This interface is also expected to be implemented by ValueExtractor implementations that implement the Comparator interface. It is expected that in most cases, the Comparator wrappers will eventually terminate at (i.e. delegate to) ValueExtractors that also implement this interface.
static ValueExtractor[]	createExtractors(String sNames) Parse a comma-delimited sequence of method names and instantiate a corresponding array of ValueExtractor objects.
Object	extract(Object oTarget) Extract a collection of values from the passed object using the underlying array of ValueExtractor objects.

Methods inherited from class com.tangosol.util.extractor.AbstractCompositeExtractor

equals, getExtractors, hashCode, readExternal, readExternal, toString, writeExternal, writeExternal

Methods inherited from class com.tangosol.util.extractor.AbstractExtractor

compare

Constructor Detail

MultiExtractor

public MultiExtractor()

Default constructor (necessary for the ExternalizableLite interface).

MultiExtractor

public MultiExtractor(ValueExtractor[] aExtractor)

Construct a MultiExtractor.

Parameters:

aExtractor - the ValueExtractor array

MultiExtractor

public MultiExtractor(String sNames)

Construct a MultiExtractor for a specified method name list.

Parameters:

sNames - a comma-delimited sequence of method names which results in a MultiExtractor that is based on a corresponding array of ValueExtractor objects; individual array elements will be either ReflectionExtractor or ChainedExtractor objects

Method Detail

extract

public Object extract(Object oTarget)

Extract a collection of values from the passed object using the underlying array of ValueExtractor objects. Note that each individual value could be an object of a standard wrapper type (for intrinsic types) or null.

Specified by:

extract in interface ValueExtractor

Specified by:

extract in class AbstractExtractor

Parameters:

oTarget - an Object to retrieve the collection of values from

Returns:

a List containing the extracted values or null if the target object itself is null

compareEntries

public int compareEntries(QueryMap.Entry entry1,
                          QueryMap.Entry entry2)

Compare two entries based on the rules specified by Comparator.

If possible, use the extract method to optimize the value extraction process.

This method is expected to be implemented by Comparator wrappers, such as ChainedComparator and InverseComparator, which simply pass on this invocation to the wrapped Comparator objects if they too implement this interface, or to invoke their default compare method passing the actual objects (not the extracted values) obtained from the extractor using the passed entries.

This interface is also expected to be implemented by ValueExtractor implementations that implement the Comparator interface. It is expected that in most cases, the Comparator wrappers will eventually terminate at (i.e. delegate to) ValueExtractors that also implement this interface.

Specified by:

compareEntries in interface QueryMapComparator

Overrides:

compareEntries in class AbstractExtractor

Parameters:

entry1 - the first entry to compare values from; read-only

entry2 - the second entry to compare values from; read-only

Returns:

a negative integer, zero, or a positive integer as the first entry denotes a value that is is less than, equal to, or greater than the value denoted by the second entry

createExtractors

public static ValueExtractor[] createExtractors(String sNames)

Parse a comma-delimited sequence of method names and instantiate a corresponding array of ValueExtractor objects. Individual array elements will be either ReflectionExtractor or ChainedExtractor objects.

Parameters:

sNames - a comma-delimited sequence of method names

Returns:

an array of ValueExtractor objects