org.gridgain.grid

Interface GridMetadataAware

All Superinterfaces:

Serializable

All Known Subinterfaces:

GridCache<K,V>, GridCacheEntry<K,V>, GridCacheEntryEx<K,V>, GridCacheProjection<K,V>, GridCacheProjectionEx<K,V>, GridCacheProxy<K,V>, GridCacheTx, GridCacheTxEx<K,V>, GridCacheTxLocalEx<K,V>, GridCacheTxProxy, GridCacheTxRemoteEx<K,V>, GridComputeJobSibling, GridComputeLoadBalancer, GridKernalContext, GridNode, GridNodeLocalMap<K,V>, GridNodeShadow

All Known Implementing Classes:

GridCacheAdapter, GridCacheEntryImpl, GridCacheEvictionEntry, GridCacheFilterEvaluationEntry, GridCacheMapEntry, GridCacheProjectionImpl, GridCacheProxyImpl, GridCacheTxAdapter, GridCacheTxLocalAdapter, GridCacheTxProxyImpl, GridComputeJobWrapper, GridDeployment, GridDhtAtomicCache, GridDhtAtomicCacheEntry, GridDhtCache, GridDhtCacheAdapter, GridDhtCacheEntry, GridDhtCacheEntryImpl, GridDhtColocatedCache, GridDhtColocatedCacheEntry, GridDhtColocatedTxLocal, GridDhtDetachedCacheEntry, GridDhtTransactionalCacheAdapter, GridDhtTxLocal, GridDhtTxLocalAdapter, GridDhtTxRemote, GridDistributedCacheAdapter, GridDistributedCacheEntry, GridDistributedTxRemoteAdapter, GridExecutorService, GridJavaLogger, GridJobContextImpl, GridJobSiblingImpl, GridKernal, GridKernalContextImpl, GridLoadBalancerAdapter, GridLocalAtomicCache, GridLocalCache, GridLocalCacheEntry, GridLoggerProxy, GridMetadataAwareAdapter, GridNearAtomicCache, GridNearCacheAdapter, GridNearCacheEntry, GridNearTransactionalCache, GridNearTxRemote, GridNodeLocalMapImpl, GridPartitionedCacheEntryImpl, GridProjectionAdapter, GridTcpDiscoveryNode

public interface GridMetadataAware
extends Serializable

Allows to attach metadata attributes to any entity that implements this interface. This promotes meta-programming technique throughout the GridGain APIs by allowing to attach and query the metadata information to top-level entities in GridGain APIs.

Note that unlike other types of attributes the metadata is explicitly local to VM. Local metadata does not have any distribution semantic and is not specifically distributed in any way. Note, however, that if object that implements this interface gets serialized and deserialized on the remote node the attachments may or may not be carried over (depending on the implementation). All classes that come with GridGain and implement this interface support proper serialization and deserialization.

For example, this may become useful for cache entries or cache transactions. Cache entry attachment can be used whenever entry needs to carry additional context and it is too expensive to keep looking that context up from a separate map by a key. For example, an expiration policy used by caches may add some expiration context to cache entries to properly expire them.

Method Summary

Methods

Modifier and Type	Method and Description
<V> V	addMeta(String name, V val) Adds a new metadata.
<V> V	addMetaIfAbsent(String name, Callable<V> c) Adds given metadata value only if it was absent.
<V> V	addMetaIfAbsent(String name, V val) Adds given metadata value only if it was absent.
<V> Map<String,V>	allMeta() Gets all metadata in this entry.
void	copyMeta(GridMetadataAware from) Copies all metadata from another instance.
void	copyMeta(Map<String,?> data) Copies all metadata from given map.
boolean	hasMeta(String name) Tests whether or not given metadata is set.
<V> boolean	hasMeta(String name, V val) Tests whether or not metadata with given name and value is set.
<V> V	meta(String name) Gets metadata by name.
<V> V	putMetaIfAbsent(String name, Callable<V> c) Adds given metadata value only if it was absent.
<V> V	putMetaIfAbsent(String name, V val) Adds given metadata value only if it was absent.
<V> V	removeMeta(String name) Removes metadata by name.
<V> boolean	removeMeta(String name, V val) Removes metadata only if its current value is equal to val passed in.
<V> boolean	replaceMeta(String name, V curVal, V newVal) Replaces given metadata with new newVal value only if its current value is equal to curVal.

Method Detail

copyMeta

void copyMeta(GridMetadataAware from)

Copies all metadata from another instance.

Parameters:

from - Metadata aware instance to copy metadata from.

copyMeta

void copyMeta(Map<String,?> data)

Copies all metadata from given map.

Parameters:

data - Map to copy metadata from.

addMeta

@Nullable
<V> V addMeta(String name,
                     V val)

Adds a new metadata.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

val - Metadata value.

Returns:

Metadata previously associated with given name, or null if there was none.

putMetaIfAbsent

@Nullable
<V> V putMetaIfAbsent(String name,
                             V val)

Adds given metadata value only if it was absent.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

val - Value to add if it's not attached already.

Returns:

null if new value was put, or current value if put didn't happen.

putMetaIfAbsent

@Nullable
<V> V putMetaIfAbsent(String name,
                             Callable<V> c)

Adds given metadata value only if it was absent.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

c - Factory closure to produce value to add if it's not attached already. Not that unlike addMeta(String, Object) method the factory closure will not be called unless the value is required and therefore value will only be created when it is actually needed.

Returns:

null if new value was put, or current value if put didn't happen.

addMetaIfAbsent

<V> V addMetaIfAbsent(String name,
                    V val)

Adds given metadata value only if it was absent. Unlike putMetaIfAbsent(String, Callable), this method always returns the latest value and never previous one.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

val - Value to add if it's not attached already.

Returns:

The value of the metadata after execution of this method.

addMetaIfAbsent

@Nullable
<V> V addMetaIfAbsent(String name,
                             @Nullable
                             Callable<V> c)

Adds given metadata value only if it was absent.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

c - Factory closure to produce value to add if it's not attached already. Not that unlike addMeta(String, Object) method the factory closure will not be called unless the value is required and therefore value will only be created when it is actually needed. If null and metadata value is missing - null will be returned from this method.

Returns:

The value of the metadata after execution of this method.

meta

<V> V meta(String name)

Gets metadata by name.

Type Parameters:

V - Type of the value.

Parameters:

name - Metadata name.

Returns:

Metadata value or null.

removeMeta

<V> V removeMeta(String name)

Removes metadata by name.

Type Parameters:

V - Type of the value.

Parameters:

name - Name of the metadata to remove.

Returns:

Value of removed metadata or null.

removeMeta

<V> boolean removeMeta(String name,
                     V val)

Removes metadata only if its current value is equal to val passed in.

Type Parameters:

V - Value type.

Parameters:

name - Name of metadata attribute.

val - Value to compare.

Returns:

True if value was removed, false otherwise.

allMeta

<V> Map<String,V> allMeta()

Gets all metadata in this entry.

Type Parameters:

V - Type of the value.

Returns:

All metadata in this entry.

hasMeta

boolean hasMeta(String name)

Tests whether or not given metadata is set.

Parameters:

name - Name of the metadata to test.

Returns:

Whether or not given metadata is set.

hasMeta

<V> boolean hasMeta(String name,
                  V val)

Tests whether or not metadata with given name and value is set. Returns true if attachment with given name it set and its value is equals to provided value. Otherwise returns false.

Type Parameters:

V - Type of the value.

Parameters:

name - Name of the metadata.

val - Value to compare. Cannot be null.

Returns:

true if metadata with given name is set and its value is equals to provided value - otherwise returns false.

replaceMeta

<V> boolean replaceMeta(String name,
                      V curVal,
                      V newVal)

Replaces given metadata with new newVal value only if its current value is equal to curVal. Otherwise, it is no-op.

Parameters:

name - Name of the metadata.

curVal - Current value to check.

newVal - New value.

Returns:

true if replacement occurred, false otherwise.