Class KnowledgeBaseServiceLocator

java.lang.Object

org.projog.core.kb.KnowledgeBaseServiceLocator

public class KnowledgeBaseServiceLocator
extends Object

Associates arbitrary objects with a KnowledgeBase.

Provides a way to implement a one-to-one relationship between a KnowledgeBase and its services. i.e. A KnowledgeBase can be associated with one, and only one, RecordedDatabase - and a RecordedDatabase can be associated with one, and only one, KnowledgeBase.

Field Summary

Fields

Modifier and Type	Field	Description
private static final Map<KnowledgeBase, KnowledgeBaseServiceLocator>	CACHE
private final KnowledgeBase	kb
private final Map<Class<?>,Object>	services

Constructor Summary

Constructors

Modifier	Constructor	Description
private	KnowledgeBaseServiceLocator(KnowledgeBase kb)

Method Summary

Modifier and Type	Method	Description
void	addInstance(Class<?> referenceType, Object instance)	Adds the specified instance with the specified referenceType as its key.
private void	assertAssignableFrom(Class<?> referenceType, Class<?> instanceType)
private void	assertInstanceOf(Class<?> referenceType, Object instance)
private Object	createInstance(Class<?> referenceType, Class<?> instanceType)
private static KnowledgeBaseServiceLocator	createServiceLocator(KnowledgeBase kb)
<T> T	getInstance(Class<?> instanceType)	Returns the Object associated the specified instanceType.
<T> T	getInstance(Class<?> referenceType, Class<?> instanceType)	Returns the Object associated the specified referenceType.
private Constructor<?>	getKnowledgeBaseArgumentConstructor(Class<?> c)
static KnowledgeBaseServiceLocator	getServiceLocator(KnowledgeBase kb)	Returns the KnowledgeBaseServiceLocator associated with the specified KnowledgeBase.
private Object	newInstance(Class<?> c)	Returns a new instance of the specified class.

Methods inherited from class Object

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

Field Details

CACHE

private static final Map<KnowledgeBase, KnowledgeBaseServiceLocator> CACHE

kb

private final KnowledgeBase kb

services

private final Map<Class<?>,Object> services

Constructor Details

KnowledgeBaseServiceLocator

private KnowledgeBaseServiceLocator(KnowledgeBase kb)

See Also:

• getServiceLocator(KnowledgeBase)

Method Details

getServiceLocator

public static KnowledgeBaseServiceLocator getServiceLocator(KnowledgeBase kb)

Returns the KnowledgeBaseServiceLocator associated with the specified KnowledgeBase.

If no KnowledgeBaseServiceLocator is already associated with the specified KnowledgeBase then a new KnowledgeBaseServiceLocator will be created.

createServiceLocator

private static KnowledgeBaseServiceLocator createServiceLocator(KnowledgeBase kb)

addInstance

public void addInstance(Class<?> referenceType,
 Object instance)

Adds the specified instance with the specified referenceType as its key.

Throws:

IllegalArgumentException - If instance is not an instance of ReferenceType.

IllegalStateException - If there is already a service associated with referenceType.

getInstance

public <T> T getInstance(Class<?> instanceType)

Returns the Object associated the specified instanceType.

If no Object is already associated with instanceType then a new instance of instanceType will be created and associated with instanceType for future use.

Throws:

RuntimeException - if an attempt to instantiate a new instance of the instanceType fails. e.g. If it does not have a public constructor that accepts either no arguments or a single KnowledgeBase argument.

getInstance

public <T> T getInstance(Class<?> referenceType,
 Class<?> instanceType)

Returns the Object associated the specified referenceType.

If no Object is already associated with referenceType then a new instance of instanceType will be created and associated with referenceType for future use.

Parameters:

referenceType - The class to use as the key to retrieve an existing service.

instanceType - The class to create a new instance of if there is no existing service associated with referenceType.

Throws:

RuntimeException - If an attempt to instantiate a new instance of the instanceType fails. e.g. If instanceType does not have a public constructor that accepts either no arguments or a single KnowledgeBase argument - or if referenceType is not the same as, nor is a superclass or superinterface of, instanceType.

createInstance

private Object createInstance(Class<?> referenceType,
 Class<?> instanceType)

assertAssignableFrom

private void assertAssignableFrom(Class<?> referenceType,
 Class<?> instanceType)

assertInstanceOf

private void assertInstanceOf(Class<?> referenceType,
 Object instance)

newInstance

private Object newInstance(Class<?> c)

Returns a new instance of the specified class.

If the class has a constructor that takes a KnowledgeBase as its single argument then an attempt is made to use that to construct the new instance - else an attempt is made to construct a new instance using the no-arg constructor.

getKnowledgeBaseArgumentConstructor

private Constructor<?> getKnowledgeBaseArgumentConstructor(Class<?> c)
                                                    throws InstantiationException,
IllegalAccessException,
InvocationTargetException

Throws:

InstantiationException

IllegalAccessException

InvocationTargetException