org.dataone.client.cache

Class LocalCache

java.lang.Object

org.dataone.client.cache.LocalCache

public class LocalCache
extends Object

LocalCache creates a local store of objects that can be locally accessed without incurring the overhead of remote service calls. Two types of caches are created, one for immutable DataONE objects (data, science metadata, and ORE packages), and one for mutable SystemMetadata objects. Each is accessed using different get/put methods. The singleton is created on first use of the instance() method, which initializes the local caches. LocalCache uses both an in-memory LRU cache for frequently accessed objects, and a longer-lived disk-based auxiliary cache for objects that have been expired from the in-memory cache. The configuration of these caches, their expiration policies, and disk locations are determined from the cache.ccf properties file.

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	getData(Identifier key) Retrieve an array of bytes from the cache, throwing NotCached if the object with the Identifier key is not in the cache.
int	getHits() Returns the cache hits, the number of times that objects are requested and found in the cache since the last time that counters were reset.
int	getMisses() Returns the cache misses, the number of times that objects are requested but are not found in the cache since the last time that counters were reset.
SystemMetadata	getSystemMetadata(Identifier key) Retrieve a SystemMetadata from the cache, throwing NotCached if the system metadata for the Identifier key is not in the cache.
static LocalCache	instance() Get the singleton instance of the LocalCache that can be used to perform cache operations.
void	putData(Identifier key, byte[] data) Put an immutable data object into the local cache by serializing it as a byte array, indexed by its unique Identifier.
void	putSystemMetadata(Identifier key, SystemMetadata sysmeta) Put a mutable SystemMetadata object into the local cache, indexed by the unique Identifier of the object that this system metadata describes.
void	resetCounters() Reset the cache hit/miss counters to 0.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

instance

public static LocalCache instance()

Get the singleton instance of the LocalCache that can be used to perform cache operations.

Returns:

the LocalCache instance

putData

public void putData(Identifier key,
           byte[] data)

Put an immutable data object into the local cache by serializing it as a byte array, indexed by its unique Identifier.

Parameters:

key - the Identifier used to index the object

data - to be cached

getData

public byte[] getData(Identifier key)
               throws NotCached

Retrieve an array of bytes from the cache, throwing NotCached if the object with the Identifier key is not in the cache.

Parameters:

key - the Identifier of the cached object to retrieve

Returns:

the array of bytes of the object

Throws:

NotCached

putSystemMetadata

public void putSystemMetadata(Identifier key,
                     SystemMetadata sysmeta)

Put a mutable SystemMetadata object into the local cache, indexed by the unique Identifier of the object that this system metadata describes. Because SystemMetadata is mutable, care should be taken to only use the cache when the calling application can be sure that it is safe to do so.

Parameters:

key - the Identifier used to index the object

SystemMetadata - to be cached

getSystemMetadata

public SystemMetadata getSystemMetadata(Identifier key)
                                 throws NotCached

Retrieve a SystemMetadata from the cache, throwing NotCached if the system metadata for the Identifier key is not in the cache. Because SystemMetadata is mutable, care should be taken to only use the cache when the calling application can be sure that it is safe to do so.

Parameters:

key - the Identifier of the cached SystemMetadata to retrieve

Returns:

the SystemMetadata of the object

Throws:

NotCached

getHits

public int getHits()

Returns the cache hits, the number of times that objects are requested and found in the cache since the last time that counters were reset.

Returns:

the hits

getMisses

public int getMisses()

Returns the cache misses, the number of times that objects are requested but are not found in the cache since the last time that counters were reset.

Returns:

the misses

resetCounters

public void resetCounters()

Reset the cache hit/miss counters to 0.