Package com.tangosol.util.transformer

Class ExtractorEventTransformer<K,​V,​E>

  • All Implemented Interfaces:
    ExternalizableLite, PortableObject, MapEventTransformer<K,​V,​E>, Serializable
    public class ExtractorEventTransformer<K,​V,​E>
extends ExternalizableHelper
implements MapEventTransformer<K,​V,​E>, ExternalizableLite, PortableObject
    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 filter = new ValueChangeEventFilter("getAccountBalance");
    ValueExtractor extractor = new MultiExtractor("getLastTransactionTime,getAccountBalance");
    MapEventTransformer transformer = new ExtractorEventTransformer(null, extractor);

    cache.addMapListener(listener, new MapEventTransformerFilter(filter, transformer), false);

    Since:
    Coherence 3.4
    Author:
    gg 2008.06.01
    See Also:
    Serialized Form

    • Constructor Detail

      • ExtractorEventTransformer

        public ExtractorEventTransformer()
        No-argument constructor for lite deserialization.

      • ExtractorEventTransformer

        public ExtractorEventTransformer​(ValueExtractor<? super V,​? extends E> extractor)
        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:
        extractor - ValueExtractor to extract MapEvent values

      • ExtractorEventTransformer

        public ExtractorEventTransformer​(String sMethod)
        Construct a ExtractorEventTransformer that transforms MapEvent's values based on the specified method name. The name could be a comma-delimited sequence of method names which will result in a MultiExtractor that is based on a corresponding array of ValueExtractor objects; individual array elements will be either ReflectionExtractor or ChainedExtractor objects.

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

        Parameters:
        sMethod - the name of the method to invoke via reflection

      • ExtractorEventTransformer

        public ExtractorEventTransformer​(ValueExtractor<? super V,​? extends E> extractorOld,
                                 ValueExtractor<? super V,​? extends E> extractorNew)
        Construct a ExtractorEventTransformer that transforms MapEvent values based on the specified extractors. Passing null indicates that the corresponding values should be skipped completely.
        Parameters:
        extractorOld - extractor to extract the OldValue property(s)
        extractorNew - extractor to extract the NewValue property(s)

    • Method Detail

      • getOldValueExtractor

        public ValueExtractor getOldValueExtractor()
        Return a ValueExtractor used to transfrom the event's OldValue.
        Returns:
        an extractor from the OldValue

      • getNewValueExtractor

        public ValueExtractor getNewValueExtractor()
        Return a ValueExtractor used to transfrom the event's NewValue.
        Returns:
        an extractor from the NewValue

      • transform

        public MapEvent<K,​E> transform​(MapEvent<K,​V> event)
        Transform the specified MapEvent using the corresponding extractors.
        Specified by:
        transform in interface MapEventTransformer<K,​V,​E>
        Parameters:
        event - MapEvent object to transform
        Returns:
        a modified MapEvent object that contains extracted values

      • readExternal

        public void readExternal​(DataInput in)
                  throws IOException
        Restore the contents of this object by loading the object's state from the passed DataInput object.
        Specified by:
        readExternal in interface ExternalizableLite
        Parameters:
        in - the DataInput stream to read data from in order to restore the state of this object
        Throws:
        IOException - if an I/O exception occurs
        NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

      • writeExternal

        public void writeExternal​(DataOutput out)
                   throws IOException
        Save the contents of this object by storing the object's state into the passed DataOutput object.
        Specified by:
        writeExternal in interface ExternalizableLite
        Parameters:
        out - the DataOutput stream to write the state of this object to
        Throws:
        IOException - if an I/O exception occurs

      • readExternal

        public void readExternal​(PofReader in)
                  throws 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:
        IOException - if an I/O error occurs

      • writeExternal

        public void writeExternal​(PofWriter out)
                   throws 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:
        IOException - if an I/O error occurs

      • equals

        public boolean equals​(Object o)
        Compare the ExtractorEventTransformer with another object to determine equality.
        Overrides:
        equals in class Object
        Returns:
        true iff this ExtractorEventTransformer and the passed object are equivalent

      • hashCode

        public int hashCode()
        Determine a hash value for the ExtractorEventTransformer object according to the general Object.hashCode() contract.
        Overrides:
        hashCode in class Object
        Returns:
        an integer hash value for this object

      • toString

        public String toString()
        Provide a human-readable representation of this object.
        Overrides:
        toString in class Object
        Returns:
        a String whose contents represent the value of this object