Oracle Coherence for C++ API: ExtractorEventTransformer Class Reference

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 void

toStream (std::ostream &out) const

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

coherence::lang::operator<<(std::ostream, Object::View) is defined and will call into the toStream 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.

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

 String::Handle hs = COH_TO_STRING(vKey << " = " << vValue);

Parameters:

out

the stream used to output the description

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