org.jboss.cache.commands.read
Class ExistsCommand

java.lang.Object
  org.jboss.cache.commands.read.AbstractDataCommand
      org.jboss.cache.commands.read.ExistsCommand

All Implemented Interfaces:

DataCommand, ReplicableCommand, VisitableCommand

public class ExistsCommand
extends AbstractDataCommand

Checks whether a given node exists in current in-memory state of the cache. Does not acquire any locks in doing so (result may be dirty read). Does not attempt to load nodes from a cache loader (may return false if a node has been evicted).

Specifically used by the ClusteredCacheLoader to implement CacheLoader.exists(org.jboss.cache.Fqn)

This is the equivalent of the old MethodCallDefinitions.existsMethod method call from 2.1.x.

Since:

2.2.0

Author:

Mircea.Markus@jboss.com

Field Summary

static int

METHOD_ID

Fields inherited from class org.jboss.cache.commands.read.AbstractDataCommand

dataContainer, fqn

Constructor Summary

ExistsCommand()

ExistsCommand(Fqn fqn)

Method Summary

Object	acceptVisitor(InvocationContext ctx, Visitor visitor) Accept a visitor, and return the result of accepting this visitor.
int	getCommandId() Used by marshallers to convert this command into an id for streaming.
Object	perform(InvocationContext ctx) Checks whether a node represented by a given Fqn exists.

Methods inherited from class org.jboss.cache.commands.read.AbstractDataCommand

equals, getFqn, getParameters, hashCode, initialize, setParameters, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

METHOD_ID

public static final int METHOD_ID

See Also:

Constant Field Values

Constructor Detail

ExistsCommand

public ExistsCommand(Fqn fqn)

ExistsCommand

public ExistsCommand()

Method Detail

perform

public Object perform(InvocationContext ctx)

Checks whether a node represented by a given Fqn exists. Deleted and invalid nodes are not considered.

Parameters:

ctx - invocation context

Returns:

true if the node exists, false otherwise.

acceptVisitor

public Object acceptVisitor(InvocationContext ctx,
                            Visitor visitor)
                     throws Throwable

Description copied from interface: VisitableCommand

Accept a visitor, and return the result of accepting this visitor.

Parameters:

ctx - invocation context

visitor - visitor to accept

Returns:

arbitrary return value

Throws:

Throwable - in the event of problems

getCommandId

public int getCommandId()

Description copied from interface: ReplicableCommand

Used by marshallers to convert this command into an id for streaming.

Returns:

the method id of this command. This is compatible with pre-2.2.0 MethodCall ids.