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com.tangosol.util.processor
Class ConditionalPut

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

All Implemented Interfaces:

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

public class ConditionalPut

extends AbstractProcessor

implements ExternalizableLite, PortableObject

ConditionalPut is an EntryProcessor that performs an Entry.setValue operation if the specified condition is satisfied.

While the ConditionalPut 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 equivalent to methods of the ConcurrentMap interface (available with JDK 1.5).

InvocableMap	ConcurrentMap
filter = PresentFilter.INSTANCE; cache.invoke(key, new ConditionalPut(filter, value);	cache.replace(key, value);
filter = new NotFilter(PresentFilter.INSTANCE); cache.invoke(key, new ConditionalPut(filter, value));	cache.putIfAbsent(key, value);
filter = new EqualsFilter(IdentityExtractor.INSTANCE, valueOld); cache.invoke(key, new ConditionalPut(filter, valueNew));	cache.replace(key, valueOld, valueNew);

Obviously, using more specific, fine-tuned filters (rather than ones based on the IdentityExtractor) may provide additional flexibility and efficiency allowing the put operation to be performed conditionally on values of specific attributes (or even calculations) instead of the entire object.

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.
protected java.lang.Object	m_oValue Specifies the new value to update an entry with.

Constructor Summary

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

ConditionalPut(Filter filter, java.lang.Object oValue)
Construct a ConditionalPut that updates an entry with a new value if and only if the filter applied to the entry evaluates to true.

ConditionalPut(Filter filter, java.lang.Object oValue, boolean fReturn)
Construct a ConditionalPut that updates an entry with a new value if and only if the filter applied to the entry evaluates to true.

Method Summary

boolean	equals(java.lang.Object o) Compare the ConditionalPut with another object to determine equality.
int	hashCode() Determine a hash value for the ConditionalPut 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 ConditionalPut.
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_oValue

protected java.lang.Object m_oValue

Specifies the new value to update an entry with.

m_fReturn

protected boolean m_fReturn

Specifies whether or not a return value is required.

Constructor Detail

ConditionalPut

public ConditionalPut()

Default constructor (necessary for the ExternalizableLite interface).

ConditionalPut

public ConditionalPut(Filter filter,
                      java.lang.Object oValue)

Construct a ConditionalPut that updates an entry with a new value 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

oValue - a value to update an entry with

ConditionalPut

public ConditionalPut(Filter filter,
                      java.lang.Object oValue,
                      boolean fReturn)

Construct a ConditionalPut that updates an entry with a new value if and only if the filter applied to the entry evaluates to true. This processor optionally returns the current value as a result of the invocation if it has not been updated (the filter evaluated to false).

Parameters:

filter - the filter to evaluate an entry

oValue - a value to update an entry with

fReturn - specifies whether or not the processor should return the current value in case it has not been updated

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 ConditionalPut with another object to determine equality.

Returns:

true iff this ConditionalPut and the passed object are equivalent ConditionalPut processors

hashCode

public int hashCode()

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

Returns:

an integer hash value for this ConditionalPut object

toString

public java.lang.String toString()

Return a human-readable description for this ConditionalPut.

Returns:

a String description of the ConditionalPut

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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