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com.tangosol.util.processor
Class ConditionalRemove

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.processor.AbstractProcessor
com.tangosol.util.processor.ConditionalRemove

All Implemented Interfaces:

ExternalizableLite, PortableObject, InvocableMap.EntryProcessor, java.io.Serializable

public class ConditionalRemove

extends AbstractProcessor

implements ExternalizableLite, PortableObject

ConditionalRemove is an EntryProcessor that performs an Entry.remove operation if the specified condition is satisfied.

While the ConditionalRemove processing could be implemented via direct key-based QueryMap operations, it is more efficient and enforces concurrency control without explicit locking.

For example, the following operations are functionally similar, but the InvocableMap versions (a) perform significantly better for partitioned caches; (b) provide all necessary concurrency control (which is ommited from the QueryMap examples):

InvocableMap	QueryMap
cache.invoke(key, new ConditionalRemove(filter)); (*)	if (filter.evaluate(cache.get(key)) cache.remove(key);
cache.invokeAll(setKeys, new ConditionalRemove(filter));	for (Object key : setKeys) if (filter.evaluate(cache.get(key)) cache.remove(key);
cache.invokeAll(filter1, new ConditionalRemove(filter2);	for (Object key : cache.setKeys(filter1)) if (filter2.evaluate(cache.get(key)) cache.remove(key);
cache.invokeAll(filter, new ConditionalRemove(AlwaysFilter.INSTANCE));	Set setKeys = cache.keySet(filter); cache.keySet().removeAll(setKeys);

^(*) If the filter is assigned as the following: filter = new EqualsFilter(IdentityExtractor.INSTANCE, oValue);
this operation also becomes functionally equivalent to the remove method of the ConcurrentMap interface (available with JDK 1.5).

Since:

Coherence 3.2

Author:

gg 2006.03.15

Field Summary

protected Filter	m_filter The underlying filter.
protected boolean	m_fReturn Specifies whether or not a return value is required.

Constructor Summary

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

ConditionalRemove(Filter filter)
Construct a ConditionalRemove processor that removes an InvocableMap entry if and only if the filter applied to the entry evaluates to true.

ConditionalRemove(Filter filter, boolean fReturn)
Construct a ConditionalRemove processor that removes an InvocableMap entry if and only if the filter applied to the entry evaluates to true.

Method Summary

boolean	equals(java.lang.Object o) Compare the ConditionalRemove with another object to determine equality.
int	hashCode() Determine a hash value for the ConditionalRemove object according to the general Object.hashCode() contract.
java.lang.Object	process(InvocableMap.Entry entry) Process a Map.Entry object.
java.util.Map	processAll(java.util.Set setEntries) Process a Set of InvocableMap.Entry objects.
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.
java.lang.String	toString() Return a human-readable description for this ConditionalRemove.
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.

Field Detail

m_filter

protected Filter m_filter

The underlying filter.

m_fReturn

protected boolean m_fReturn

Specifies whether or not a return value is required.

Constructor Detail

ConditionalRemove

public ConditionalRemove()

Default constructor (necessary for the ExternalizableLite interface).

ConditionalRemove

public ConditionalRemove(Filter filter)

Construct a ConditionalRemove processor that removes an InvocableMap entry if and only if the filter applied to the entry evaluates to true. The result of the process(com.tangosol.util.InvocableMap.Entry) invocation does not return any result.

Parameters:

filter - the filter to evaluate an entry

ConditionalRemove

public ConditionalRemove(Filter filter,
                         boolean fReturn)

Construct a ConditionalRemove processor that removes an InvocableMap entry if and only if the filter applied to the entry evaluates to true. This processor may optionally return the current value as a result of the invocation if it has not been removed (the filter evaluated to false).

Parameters:

filter - the filter to evaluate an entry

fReturn - specifies whether or not the processor should return the current value if it has not been removed

Method Detail

process

public java.lang.Object process(InvocableMap.Entry entry)

Process a Map.Entry object.

Specified by:

process in interface InvocableMap.EntryProcessor

Parameters:

entry - the Entry to process Note: if this method throws an exception, all modifications to the supplied entry or any other entries retrieved via the BackingMapContext.getBackingMapEntry(java.lang.Object) API will be rolled back leaving all underlying values unchanged.

Returns:

the result of the processing, if any

processAll

public java.util.Map processAll(java.util.Set setEntries)

Process a Set of InvocableMap.Entry objects. This method is semantically equivalent to:

   Map mapResults = new ListMap();
   for (Iterator iter = setEntries.iterator(); iter.hasNext(); )
       {
       Entry entry = (Entry) iter.next();
       mapResults.put(entry.getKey(), process(entry));
       }
   return mapResults;
 

Note: if processAll() call throws an exception, only the entries that were removed from the setEntries would be considered successfully processed and the corresponding changes made to the underlying Map; changes made to the remaining entries or any other entries obtained from BackingMapContext.getBackingMapEntry(java.lang.Object) will not be processed.

Specified by:

processAll in interface InvocableMap.EntryProcessor

Overrides:

processAll in class AbstractProcessor

Parameters:

setEntries - a Set of InvocableMap.Entry objects to process

Returns:

a Map containing the results of the processing, up to one entry for each InvocableMap.Entry that was processed, keyed by the keys of the Map that were processed, with a corresponding value being the result of the processing for each key

equals

public boolean equals(java.lang.Object o)

Compare the ConditionalRemove with another object to determine equality.

Returns:

true iff this ConditionalRemove and the passed object are equivalent ConditionalRemove

hashCode

public int hashCode()

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

Returns:

an integer hash value for this ConditionalRemove object

toString

public java.lang.String toString()

Return a human-readable description for this ConditionalRemove.

Returns:

a String description of the ConditionalRemove processor

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

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

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

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

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