DatabaseCacheImpl (CrNiCKL database 2.0.0 API)

java.lang.Object
- ch.agent.crnickl.impl.DatabaseCacheImpl

All Implemented Interfaces:

DatabaseCache
```
public class DatabaseCacheImpl
extends Object
implements DatabaseCache
```
Default implementation of DatabaseCache. There are actually three separate caches:
1. for chronicles with a schema and for their parent chronicles
2. for the schemas referenced in the chronicles
3. for the properties referenced in the schemas
The implementation is thread-safe. The chronicle cache is an LRU cache. The assumption is that clients do not have a large number of chronicles with a non-null schema and that the maximum capacity is specified to be large enough to store all relevant chronicles. The schema and property caches always store all relevant objects, and are automatically maintained if the LRU chronicle cache requests the removal of a chronicle.
Author:

Jean-Paul Vetterli

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected class`	`DatabaseCacheImpl.ChronicleCache` ChronicleCache is an LRU cache which requests removal of the least recently accessed value when the capacity is exceeded.

Constructor Summary

Constructors
Constructor and Description
`DatabaseCacheImpl(Database db, int capacity)` Construct a `DatabaseCache` with a 0.75 load factor.
`DatabaseCacheImpl(Database db, int capacity, float loadFactor)` Construct a `DatabaseCache`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Clear the cache.
`void`	`clear(Chronicle chronicle)` Remove a chronicle from the cache if present.
`void`	`clear(Property<?> property)` Remove a property from the cache if present.
`void`	`clear(Schema schema)` Remove a schema from the cache if present.
`void`	`clear(ValueType<?> valueType)` Remove a value type from the cache if present.
`ChronicleImpl`	`lookUpChronicle(String name)` Look up a chronicle in the cache by name.
`ChronicleImpl`	`lookUpChronicle(Surrogate surrogate)` Look up a chronicle in the cache.
`Property<?>`	`lookUpProperty(String name)` Look up a property in the cache by name.
`void`	`setMessageListener(MessageListener messageListener)` Set a message listener.
`int`	`size()` Return the number of chronicles currently in the cache.
`ChronicleImpl`	`store(ChronicleImpl entity)` Store a chronicle in the cache and return a copy.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DatabaseCacheImpl
```
public DatabaseCacheImpl(Database db,
                         int capacity,
                         float loadFactor)
```
    Construct a DatabaseCache.
    
    Parameters:
    
    db - the database being cached
    
    capacity - a positive number
    
    loadFactor - a number between 0 and 1
  - DatabaseCacheImpl
```
public DatabaseCacheImpl(Database db,
                         int capacity)
```
    Construct a DatabaseCache with a 0.75 load factor.
    
    Parameters:
    
    db - the database being cached
    
    capacity - a positive number
- Method Detail
  - setMessageListener
```
public void setMessageListener(MessageListener messageListener)
```
    Set a message listener. When a message listener is defined, the cache can issue messages notify of cache removals. Monitoring such messages is useful for tuning cache parameters.
    
    Parameters:
    
    messageListener - a message listener
  - lookUpChronicle
```
public ChronicleImpl lookUpChronicle(Surrogate surrogate)
```
    Description copied from interface: DatabaseCache
    
    Look up a chronicle in the cache. Return null if not found.
    
    Specified by:
    
    lookUpChronicle in interface DatabaseCache
    
    Parameters:
    
    surrogate - a chronicle surrogate
    
    Returns:
    
    a chronicle or null
  - lookUpChronicle
```
public ChronicleImpl lookUpChronicle(String name)
```
    Description copied from interface: DatabaseCache
    
    Look up a chronicle in the cache by name. Return null if not found.
    
    Specified by:
    
    lookUpChronicle in interface DatabaseCache
    
    Parameters:
    
    name - a string
    
    Returns:
    
    a chronicle or null
  - lookUpProperty
```
public Property<?> lookUpProperty(String name)
                           throws T2DBException
```
    Description copied from interface: DatabaseCache
    
    Look up a property in the cache by name. If not in the cache get it from the database. Throw an exception if not found. This method is meant for accessing "built-in" properties
    
    Specified by:
    
    lookUpProperty in interface DatabaseCache
    
    Parameters:
    
    name - a string
    
    Returns:
    
    a property
    
    Throws:
    
    T2DBException
  - store
```
public ChronicleImpl store(ChronicleImpl entity)
                    throws T2DBException
```
    Description copied from interface: DatabaseCache
    
    Store a chronicle in the cache and return a copy. Return null if the chronicle was not kept in the cache for some reason.
    
    Specified by:
    
    store in interface DatabaseCache
    
    Parameters:
    
    entity - a chronicle
    
    Returns:
    
    a chronicle or null
    
    Throws:
    
    T2DBException
  - size
```
public int size()
```
    Description copied from interface: DatabaseCache
    
    Return the number of chronicles currently in the cache.
    
    Specified by:
    
    size in interface DatabaseCache
    
    Returns:
    
    the number of chronicles in the cache
  - clear
```
public void clear()
```
    Description copied from interface: DatabaseCache
    
    Clear the cache.
    
    Specified by:
    
    clear in interface DatabaseCache
  - clear
```
public void clear(Chronicle chronicle)
```
    Description copied from interface: DatabaseCache
    
    Remove a chronicle from the cache if present. This method must be called before renaming or deleting a chronicle.
    
    Specified by:
    
    clear in interface DatabaseCache
    
    Parameters:
    
    chronicle - a chronicle
  - clear
```
public void clear(Schema schema)
```
    Description copied from interface: DatabaseCache
    
    Remove a schema from the cache if present. This method must be called before renaming or deleting a schema.
    
    Specified by:
    
    clear in interface DatabaseCache
    
    Parameters:
    
    schema - a schema
  - clear
```
public void clear(Property<?> property)
```
    Description copied from interface: DatabaseCache
    
    Remove a property from the cache if present. This method must be called before renaming or deleting a property.
    
    Specified by:
    
    clear in interface DatabaseCache
    
    Parameters:
    
    property - a property
  - clear
```
public void clear(ValueType<?> valueType)
```
    Description copied from interface: DatabaseCache
    
    Remove a value type from the cache if present. This method must be called before modifying or deleting a value type.
    
    Specified by:
    
    clear in interface DatabaseCache
    
    Parameters:
    
    valueType - a valueType

Class DatabaseCacheImpl

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DatabaseCacheImpl

DatabaseCacheImpl

Method Detail

setMessageListener

lookUpChronicle

lookUpChronicle

lookUpProperty

store

size

clear

clear

clear

clear

clear