org.eclipse.viatra.query.runtime.api

Class ViatraQueryEngineManager

java.lang.Object

org.eclipse.viatra.query.runtime.api.ViatraQueryEngineManager

public class ViatraQueryEngineManager
extends java.lang.Object

Global registry of active VIATRA Query Engines.

Manages an ViatraQueryEngine for each model (more precisely scope), that is created on demand. Managed engines are shared between clients querying the same model.

It is also possible to create private, unmanaged engines that are not shared between clients.

Only weak references are retained on the managed engines. So if there are no other references to the matchers or the engine, they can eventually be GC'ed, and they won't block the model from being GC'ed either.

Method Summary

Modifier and Type	Method and Description
void	addQueryEngineInitializationListener(ViatraQueryEngineInitializationListener listener) Registers a listener for new engine initialization.
java.util.Set<ViatraQueryEngine>	getExistingQueryEngines() Collects all ViatraQueryEngine instances that still exist.
static ViatraQueryEngineManager	getInstance()
ViatraQueryEngine	getQueryEngine(QueryScope scope) Creates a managed VIATRA Query Engine at a given scope (e.g.
ViatraQueryEngine	getQueryEngine(QueryScope scope, ViatraQueryEngineOptions options) Creates a managed VIATRA Query Engine at a given scope (e.g.
ViatraQueryEngine	getQueryEngineIfExists(QueryScope scope) Retrieves an already existing managed VIATRA Query Engine.
protected void	notifyInitializationListeners(AdvancedViatraQueryEngine engine) Notifies listeners that a new engine has been initialized.
void	removeQueryEngineInitializationListener(ViatraQueryEngineInitializationListener listener) Removes a registered listener added with addQueryEngineInitializationListener(org.eclipse.viatra.query.runtime.api.ViatraQueryEngineInitializationListener)

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static ViatraQueryEngineManager getInstance()

Returns:

the singleton instance

getQueryEngine

public ViatraQueryEngine getQueryEngine(QueryScope scope)
                                 throws ViatraQueryException

Creates a managed VIATRA Query Engine at a given scope (e.g. an EMF Resource or ResourceSet, as in EMFScope) or retrieves an already existing one. Repeated invocations for a single model root will return the same engine. Consequently, the engine will be reused between different clients querying the same model, providing performance benefits.

The match set of any patterns will be incrementally refreshed upon updates from this scope.

Parameters:

scope - the scope of query evaluation; the definition of the set of model elements that this engine is operates on. Provide e.g. a EMFScope for evaluating queries on an EMF model.

Returns:

a new or previously existing engine

Throws:

ViatraQueryException

getQueryEngine

public ViatraQueryEngine getQueryEngine(QueryScope scope,
                                        ViatraQueryEngineOptions options)
                                 throws ViatraQueryException

Creates a managed VIATRA Query Engine at a given scope (e.g. an EMF Resource or ResourceSet, as in EMFScope) or retrieves an already existing one. Repeated invocations for a single model root will return the same engine. Consequently, the engine will be reused between different clients querying the same model, providing performance benefits.

The match set of any patterns will be incrementally refreshed upon updates from this scope.

Parameters:

scope - the scope of query evaluation; the definition of the set of model elements that this engine is operates on. Provide e.g. a EMFScope for evaluating queries on an EMF model.

Returns:

a new or previously existing engine

Throws:

ViatraQueryException

Since:

1.4

getQueryEngineIfExists

public ViatraQueryEngine getQueryEngineIfExists(QueryScope scope)

Retrieves an already existing managed VIATRA Query Engine.

Parameters:

scope - the scope of query evaluation; the definition of the set of model elements that this engine is operates on. Provide e.g. a EMFScope for evaluating queries on an EMF model.

Returns:

a previously existing engine, or null if no engine is active for the given EMF model root

getExistingQueryEngines

public java.util.Set<ViatraQueryEngine> getExistingQueryEngines()

Collects all ViatraQueryEngine instances that still exist.

Returns:

set of engines if there is any, otherwise EMTPY_SET

addQueryEngineInitializationListener

public void addQueryEngineInitializationListener(ViatraQueryEngineInitializationListener listener)

Registers a listener for new engine initialization.

For removal, use removeQueryEngineInitializationListener(org.eclipse.viatra.query.runtime.api.ViatraQueryEngineInitializationListener)

Parameters:

listener - the listener to register

removeQueryEngineInitializationListener

public void removeQueryEngineInitializationListener(ViatraQueryEngineInitializationListener listener)

Removes a registered listener added with addQueryEngineInitializationListener(org.eclipse.viatra.query.runtime.api.ViatraQueryEngineInitializationListener)

Parameters:

listener -

notifyInitializationListeners

protected void notifyInitializationListeners(AdvancedViatraQueryEngine engine)

Notifies listeners that a new engine has been initialized.

Parameters:

engine - the initialized engine