Oracle® Fusion Middleware C++ API Reference for Oracle Coherence
14c (14.1.1.0.0)
F23533-01

coherence::util::transformer::ExtractorEventTransformer

ExtractorEventTransformer Class Reference

#include <coherence/util/transformer/ExtractorEventTransformer.hpp>

Inherits Object, PortableObject, and MapEventTransformer.

Detailed Description

ExtractorEventTransformer is a special purpose MapEventTransformer implementation that transforms emitted events, extracting one or more properties from either the OldValue or the NewValue.

This transformation will generally result in the change of the values' data type.

Example: the following code will register a listener to receive events only if the value of the AccountBalance property changes. The transformed event's NewValue will be a List containing the LastTransactionTime and AccountBalance properties. The OldValue will always be null.

    Filter::View vFilter =
       ValueChangeEventFilter::create("getAccountBalance");
    ValueExtractor::View vExtractor =
       MultiExtractor::create(MultiExtractor::createExtractors(
           "getLastTransactionTime,getAccountBalance"));
    MapEventTransformer::Handle hTransformer =
       ExtractorEventTransformer::create(NULL, vExtractor);

    cache->addMapListener(listener,
       MapEventTransformerFilter::create(vFilter, hTransformer), false);

Author:: djl 2008.06.17

Public Types

typedef spec::Handle Handle

ExtractorEventTransformer Handle definition.

typedef spec::View View

ExtractorEventTransformer View definition.

typedef spec::Holder Holder

ExtractorEventTransformer Holder definition.

Public Member Functions

virtual MapEvent::Handle transform (MapEvent::Handle hEvent) const

Transform the specified MapEvent.

The values contained by the returned MapEvent object will be the ones given (sent) to the corresponding listener.

Parameters:

hEvent

the original MapEvent object

Returns:: modified MapEvent object or NULL to discard the event

virtual void readExternal (PofReader::Handle hIn)

virtual void writeExternal (PofWriter::Handle hOut) const

virtual bool equals (Object::View v) const

virtual size32_t hashCode () const

Return a hash code value for the Object.

This method is supported for the benefit of hash-based containers.

The general contract of hashCode is:

Whenever it is invoked on the same Object more than once during an execution of an application, the hashCode method must consistently return the same value, provided no information used in equals comparisons on the object is modified. This value need not remain consistent from one execution of an application to another execution of the same application.
If two Objects are equal according to the equals method, then calling the hashCode method on each of the two Objects must produce the same value.
It is not required that if two Objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct results. However, the programmer should be aware that producing distinct results for unequal objects may improve the performance of hash-based containers.

The default implementation is identity based.

Returns:: a hash code value for this Object

virtual TypedHandle
< const String > toString () const

Output a human-readable description of this Object to the given stream.

Note that when overriding this method the return type must be TypedHandle<const String> rather then String::View. These two types are assignment compatible but not equivalent and declaring the override with String::View will not be a compatible override.

coherence::lang::operator<<(std::ostream, Object::View) is defined and will call into the toString method, to output Objects. If a managed String object is desired, the COH_TO_STRING macro can be used to build up a String from streamable contents and is generally how toString() will be implemented.

 Object::View vKey   = ...
 Object::View vValue = ...
 std::cout << vKey << " = " << vValue << std::endl;

 String::View vs = COH_TO_STRING(vKey << " = " << vValue);

The COH_TO_STRING macro is also the most common way to implement the toString method. For example:

 virtual TypedHandle<const String> Person::toString() const
     {
     return COH_TO_STRING("Name: " << f_sName << " SSN: " << f_nSSN);
     }

Returns:: a string representation of this object

virtual
ValueExtractor::View getOldValueExtractor () const

Return a ValueExtractor used to transfrom the event's OldValue.

virtual
ValueExtractor::View getNewValueExtractor () const

Return a ValueExtractor used to transfrom the event's NewValue.

Protected Member Functions

ExtractorEventTransformer ()

Default constructor (necessary for the PortableObject interface).

ExtractorEventTransformer (ValueExtractor::View vExtractor)

Construct a ExtractorEventTransformer that transforms MapEvent values based on the specified extractor.

ExtractorEventTransformer (ValueExtractor::View vExtractorOld, ValueExtractor::View vExtractorNew)

Construct a ExtractorEventTransformer that transforms MapEvent values based on the specified extractors.

Constructor & Destructor Documentation

ExtractorEventTransformer ( ValueExtractor::View vExtractor ) [protected]

Construct a ExtractorEventTransformer that transforms MapEvent values based on the specified extractor.

Note: The specified extractor will be applied to both old and new values.

Parameters:

vExtractor

ValueExtractor to extract MapEvent values

ExtractorEventTransformer	(	ValueExtractor::View	vExtractorOld,
		ValueExtractor::View	vExtractorNew
	)			`[protected]`

Construct a ExtractorEventTransformer that transforms MapEvent values based on the specified extractors.

Passing null indicates that the corresponding values should be skipped completely.

Parameters:

	vExtractorOld	extractor to extract the OldValue property(s)
	vExtractorNew	extractor to extract the NewValue property(s)

Member Function Documentation

virtual ValueExtractor::View getOldValueExtractor ( ) const [virtual]

Return a ValueExtractor used to transfrom the event's OldValue.

Returns:: an extractor from the OldValue

virtual ValueExtractor::View getNewValueExtractor ( ) const [virtual]

Return a ValueExtractor used to transfrom the event's NewValue.

Returns:: an extractor from the NewValue

The documentation for this class was generated from the following file:

coherence/util/transformer/ExtractorEventTransformer.hpp