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com.tangosol.util.extractor
Class PofExtractor

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

All Implemented Interfaces:

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

public class PofExtractor

extends AbstractExtractor

implements PortableObject

POF-based ValueExtractor implementation. PofExtractor takes advantage of POF's indexed state to extract part of an object without needing to deserialize the entire object.

POF uses a compact form in the serialized value when possible. For example, some numeric values are represented as special POF intrinsic types in which the type implies the value. As a result, POF requires the receiver of a value to have implicit knowledge of the type. PofExtractor uses the class supplied in the constructor as the source of the type information. If the class is null, PofExtractor will infer the type from the serialized state.

Example where extracted value is double:

     PofExtractor extractor = new PofExtractor(double.class, 3);
 

Example where extracted value should be inferred:

     PofExtractor extractor = new PofExtractor(null, 4);
 

Since:

Coherence 3.5

Author:

as 2009.02.14

Field Summary

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

KEY, m_nTarget, VALUE

Constructor Summary

PofExtractor()
Default constructor (necessary for the PortableObject interface).

PofExtractor(java.lang.Class clz, int iProp)
Constructs a PofExtractor based on a property index.

PofExtractor(java.lang.Class clz, PofNavigator navigator)
Constructs a PofExtractor based on a POF navigator.

PofExtractor(java.lang.Class clz, PofNavigator navigator, int nTarget)
Constructs a PofExtractor based on a POF navigator and the entry extraction target.

Method Summary

boolean	equals(java.lang.Object o) Compare the PofExtractor with another object to determine equality.
java.lang.Object	extractFromEntry(java.util.Map.Entry entry) Extracts the value from the passed Entry object.
java.lang.Object	extractOriginalFromEntry(MapTrigger.Entry entry) Extract the value from the "original value" of the passed Entry object.
java.lang.Class	getClassExtracted() Obtain the Class of the extracted value.
PofNavigator	getNavigator() Obtain the POF navigator for this extractor.
protected int	getPofTypeId(PofContext ctx) Compute the expected pof type id based on the class.
int	hashCode() Determine a hash value for the PofExtractor object according to the general Object.hashCode() contract.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
java.lang.String	toString() Return a human-readable description for this PofExtractor.
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.AbstractExtractor

compare, compareEntries, extract

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

Constructor Detail

PofExtractor

public PofExtractor()

Default constructor (necessary for the PortableObject interface).

PofExtractor

public PofExtractor(java.lang.Class clz,
                    int iProp)

Constructs a PofExtractor based on a property index.

This constructor is equivalent to:

   PofExtractor extractor =
       new PofExtractor(clz, new SimplePofPath(iProp), VALUE);
 

Parameters:

clz - the required class of the extracted value or null if the class is to be inferred from the serialized state

iProp - property index

PofExtractor

public PofExtractor(java.lang.Class clz,
                    PofNavigator navigator)

Constructs a PofExtractor based on a POF navigator.

This constructor is equivalent to:

   PofExtractor extractor =
       new PofExtractor(clz, navigator, VALUE);
 

Parameters:

clz - the required class of the extracted value or null if the class is to be inferred from the serialized state

navigator - POF navigator

PofExtractor

public PofExtractor(java.lang.Class clz,
                    PofNavigator navigator,
                    int nTarget)

Constructs a PofExtractor based on a POF navigator and the entry extraction target.

Parameters:

clz - the required class of the extracted value or null if the class is to be inferred from the serialized state

navigator - POF navigator

nTarget - one of the AbstractExtractor.VALUE or AbstractExtractor.KEY values

Method Detail

extractFromEntry

public java.lang.Object extractFromEntry(java.util.Map.Entry entry)

Extracts the value from the passed Entry object.

It is expected that this extractor will only be used against POF-encoded entries implementing BinaryEntry interface.

Overrides:

extractFromEntry in class AbstractExtractor

Parameters:

entry - an Entry object to extract a value from

Returns:

the extracted value

Throws:

java.lang.UnsupportedOperationException - if the specified Entry is not a POF-encoded BinaryEntry or the serializer is not a PofContext

java.lang.ClassCastException - if the extracted value is incompatible with the specified class

extractOriginalFromEntry

public java.lang.Object extractOriginalFromEntry(MapTrigger.Entry entry)

Description copied from class: AbstractExtractor

Extract the value from the "original value" of the passed Entry object. This method's conventions are exactly the same as for the AbstractExtractor.extractFromEntry(java.util.Map.Entry) method.

Overrides:

extractOriginalFromEntry in class AbstractExtractor

Parameters:

entry - an Entry object whose original value should be used to extract the desired value from

Returns:

the extracted value or null if the original value is not present

getNavigator

public PofNavigator getNavigator()

Obtain the POF navigator for this extractor.

Returns:

the POF navigator

getClassExtracted

public java.lang.Class getClassExtracted()

Obtain the Class of the extracted value.

Returns:

the expected Class

equals

public boolean equals(java.lang.Object o)

Compare the PofExtractor with another object to determine equality. Two PofExtractor objects are considered equal iff their navigators are equal and they have the same target (key or value).

Specified by:

equals in interface ValueExtractor

Specified by:

equals in interface java.util.Comparator

Parameters:

o - the reference object with which to compare

Returns:

true iff this PofExtractor and the passed object are equivalent

See Also:

Object.equals(java.lang.Object), Object.hashCode()

hashCode

public int hashCode()

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

Specified by:

hashCode in interface ValueExtractor

Returns:

an integer hash value for this PofExtractor object

toString

public java.lang.String toString()

Return a human-readable description for this PofExtractor.

Specified by:

toString in interface ValueExtractor

Returns:

a String description of the PofExtractor

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

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

Parameters:

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

Throws:

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

getPofTypeId

protected int getPofTypeId(PofContext ctx)

Compute the expected pof type id based on the class.

Parameters:

ctx - pof context

Returns:

pof type id or T_UNKNOWN if the class is null.

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