org.projog.core.kb

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.

Method Summary

Modifier and Type	Method and Description
void	addInstance(Class<?> referenceType, Object instance) Adds the specified instance with the specified referenceType as its key.
<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.
static KnowledgeBaseServiceLocator	getServiceLocator(KnowledgeBase kb) Returns the KnowledgeBaseServiceLocator associated with the specified KnowledgeBase.

Methods inherited from class java.lang.Object

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

Method Detail

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.

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.