com.tangosol.util.extractor
Class ComparisonValueExtractor

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.util.BitHelper
          com.tangosol.util.ExternalizableHelper
              com.tangosol.util.extractor.AbstractExtractor
                  com.tangosol.util.extractor.AbstractCompositeExtractor
                      com.tangosol.util.extractor.ComparisonValueExtractor

All Implemented Interfaces:

ExternalizableLite, PortableObject, QueryMapComparator, ValueExtractor, java.io.Serializable, java.util.Comparator

public class ComparisonValueExtractor
extends AbstractCompositeExtractor

A synthetic ValueExtractor that returns a result of comparison between two values extracted from the same target. In a most general case, the extracted value represents an Integer value calculated accordingly to the contract of Comparable.compareTo(java.lang.Object) or Comparator.compare(java.lang.Object, java.lang.Object) methods. However, in more specific cases, when the compared values are of common numeric type, the ComparisonValueExtractor will return a numeric difference between those values. The Java type of the comparing values will dictate the Java type of the result.

For example, lets assume that a cache contains business objects that have two properties: SellPrice and BuyPrice (both double). Then, to query for all objects that have SellPrice less than BuyPrice we would use the following:

 ValueExtractor extractDiff = new ComparisonValueExtractor(
   new ReflectionExtractor("getSellPrice"),
   new ReflectionExtractor("getBuyPrice"));
 Filter filter = new LessFilter(extractDiff, new Double(0.0));
 Set entries = cache.entrySet(filter);
 

Since:

Coherence 3.4

Author:

gg 2008.02.15

Field Summary

protected java.util.Comparator

m_comparator An underlying Comparator object (optional).

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

m_aExtractor

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

KEY, m_nTarget, VALUE

Constructor Summary

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

ComparisonValueExtractor(java.lang.String sMethod1, java.lang.String sMethod2)
Constuct a ComparisonValueExtractor based on two method names.

ComparisonValueExtractor(java.lang.String sMethod1, java.lang.String sMethod2, java.util.Comparator comp)
Constuct a ComparisonValueExtractor based on two method names and a Comparator object.

ComparisonValueExtractor(ValueExtractor ve1, ValueExtractor ve2)
Constuct a ComparisonValueExtractor based on two specified extractors.

ComparisonValueExtractor(ValueExtractor ve1, ValueExtractor ve2, java.util.Comparator comp)
Constuct a ComparisonValueExtractor based on two specified extractors and a Comparator object.

Method Summary

java.lang.Object	extract(java.lang.Object oTarget) Extract the value from the passed object. The returned value may be null. For intrinsic types, the returned value is expected to be a standard wrapper type in the same manner that reflection works; for example, int would be returned as a java.lang.Integer.
java.util.Comparator	getComparator() Return a Comparator used by this extractor.
void	readExternal(java.io.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.
void	writeExternal(java.io.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.extractor.AbstractCompositeExtractor

equals, getExtractors, hashCode, toString

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

compare, compareEntries, extractFromEntry

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_comparator

protected java.util.Comparator m_comparator

An underlying Comparator object (optional).

Constructor Detail

ComparisonValueExtractor

public ComparisonValueExtractor()

Default constructor (necessary for the ExternalizableLite interface).

ComparisonValueExtractor

public ComparisonValueExtractor(java.lang.String sMethod1,
                                java.lang.String sMethod2)

Constuct a ComparisonValueExtractor based on two method names. Note: values returned by both methods must be Comparable.

Parameters:

sMethod1 - the name of the first method to invoke via reflection

sMethod2 - the name of the second method to invoke via reflection

ComparisonValueExtractor

public ComparisonValueExtractor(java.lang.String sMethod1,
                                java.lang.String sMethod2,
                                java.util.Comparator comp)

Constuct a ComparisonValueExtractor based on two method names and a Comparator object.

Parameters:

sMethod1 - the name of the first method to invoke via reflection

sMethod2 - the name of the second method to invoke via reflection

comp - the comparator used to compare the extracted values (optional)

ComparisonValueExtractor

public ComparisonValueExtractor(ValueExtractor ve1,
                                ValueExtractor ve2)

Constuct a ComparisonValueExtractor based on two specified extractors. Note: values returned by both extractors must be Comparable.

Parameters:

ve1 - the ValueExtractor for the first value

ve2 - the ValueExtractor for the second value

ComparisonValueExtractor

public ComparisonValueExtractor(ValueExtractor ve1,
                                ValueExtractor ve2,
                                java.util.Comparator comp)

Constuct a ComparisonValueExtractor based on two specified extractors and a Comparator object.

Parameters:

ve1 - the ValueExtractor for the first value

ve2 - the ValueExtractor for the second value

comp - the comparator used to compare the extracted values (optional)

Method Detail

getComparator

public java.util.Comparator getComparator()

Return a Comparator used by this extractor.

Returns:

a Comparator used by this extractor; null if the natural value comparison should be used

extract

public java.lang.Object extract(java.lang.Object oTarget)

Extract the value from the passed object. The returned value may be null. For intrinsic types, the returned value is expected to be a standard wrapper type in the same manner that reflection works; for example, int would be returned as a java.lang.Integer.

Specified by:

extract in interface ValueExtractor

Overrides:

extract in class AbstractExtractor

Parameters:

oTarget - an Object to retrieve the value from

Returns:

the extracted value as an Object; null is an acceptable value

readExternal

public void readExternal(java.io.DataInput in)
                  throws java.io.IOException

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

Specified by:

readExternal in interface ExternalizableLite

Overrides:

readExternal in class AbstractCompositeExtractor

Parameters:

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

Throws:

java.io.IOException - if an I/O exception occurs

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

writeExternal

public void writeExternal(java.io.DataOutput out)
                   throws java.io.IOException

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

Specified by:

writeExternal in interface ExternalizableLite

Overrides:

writeExternal in class AbstractCompositeExtractor

Parameters:

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

Throws:

java.io.IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws java.io.IOException

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

Specified by:

readExternal in interface PortableObject

Overrides:

readExternal in class AbstractCompositeExtractor

Parameters:

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

Throws:

java.io.IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws java.io.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

Overrides:

writeExternal in class AbstractCompositeExtractor

Parameters:

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

Throws:

java.io.IOException - if an I/O error occurs