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/*******************************************************************************
* Copyright (c) 2009, 2010 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.jpa.core.jpa2;
import java.io.Serializable;
/**
* JPA 2.0 Canonical Metamodel synchronizer.
* <p>
* Notes:
* <ul><li>
* When a JPA project is first created (e.g. when the user adds the JPA
* Facet to a Faceted project or when a workspace containing a JPA project is
* opened), if it is configured to generate the
* Canonical Metamodel (i.e. its metamodel source folder is non-null), it will
* first discover what metamodel classes are already present in the metamodel
* source folder. Any class appropriately annotated with
* <code>javax.persistence.metamodel.StaticMetamodel</code>
* and <code>javax.annotation.Generated</code>
* will be added to the Canonical Metamodel
* (see {@link org.eclipse.jpt.jpa.core.internal.resource.java.source.SourcePersistentType#isGeneratedMetamodel()}).
* Once the JPA project's context model is constructed, a new Canonical
* Metamodel is generated and merged with the classes already present in the
* metamodel source folder.
* </li><li>
* When a JPA project's metamodel source folder setting is cleared, the Canonical
* Metamodel is cleared from the context model, but the generated source files are
* left in place.
* </li><li>
* When a JPA project's metamodel source folder is set to a non-null value,
* like when a JPA project is first created, the resulting Canonical Metamodel
* will be merged with whatever is already present in the folder.
* </li></ul>
* <p>
* Provisional API: This interface is part of an interim API that is still
* under development and expected to change significantly before reaching
* stability. It is available at this early stage to solicit feedback from
* pioneering adopters on the understanding that any code that uses this API
* will almost certainly be broken (repeatedly) as the API evolves.
*
* @version 2.3
* @since 2.3
*/
public interface MetamodelSynchronizer {
void initializeMetamodel();
void synchronizeMetamodel();
void disposeMetamodel();
/**
* Singleton implemetation of the metamodel synchronizer interface that
* does nothing. (Not sure we need this....)
*/
final class Null implements MetamodelSynchronizer, Serializable {
public static final MetamodelSynchronizer INSTANCE = new Null();
public static MetamodelSynchronizer instance() {
return INSTANCE;
}
// ensure single instance
private Null() {
super();
}
public void initializeMetamodel() {
// do nothing
}
public void synchronizeMetamodel() {
// do nothing
}
public void disposeMetamodel() {
// do nothing
}
@Override
public String toString() {
return "MetamodelSynchronizer.Null"; //$NON-NLS-1$
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
}
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