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Cayenne Object Persistence Framework
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
****************************************************************/
package org.apache.cayenne;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.apache.cayenne.event.EventManager;
import org.apache.cayenne.graph.GraphDiff;
import org.apache.cayenne.graph.GraphManager;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.map.ObjEntity;
import org.apache.cayenne.property.ClassDescriptor;
import org.apache.cayenne.query.ObjectIdQuery;
import org.apache.cayenne.query.Query;
import org.apache.cayenne.util.EventUtil;
/**
* A default generic implementation of ObjectContext suitable for accessing Cayenne from
* either an ORM or a client tiers. Communicates with Cayenne via a
* {@link org.apache.cayenne.DataChannel}.
*
* @since 1.2
* @author Andrus Adamchik
*/
public class CayenneContext implements ObjectContext {
// if we are to pass CayenneContext around, channel should be left alone and
// reinjected later if needed
protected transient DataChannel channel;
protected EntityResolver entityResolver;
CayenneContextGraphManager graphManager;
// note that it is important to reuse the same action within the property change
// thread to avoid a loop of "propertyChange" calls on handling reverse relationships.
// Here we go further and make action a thread-safe ivar that tracks its own thread
// state.
CayenneContextGraphAction graphAction;
// object that merges "backdoor" changes that come from the channel.
CayenneContextMergeHandler mergeHandler;
/**
* Creates a new CayenneContext with no channel and disabled graph events.
*/
public CayenneContext() {
this(null);
}
/**
* Creates a new CayenneContext, initializaing it with a channel instance.
* CayenneContext created using this constructor WILL NOT broadcast graph change
* events.
*/
public CayenneContext(DataChannel channel) {
this(channel, false, false);
}
/**
* Creates a new CayenneContext, initializaing it with a channel. If
* graphEventsEnabled is true, this context will broadcast GraphEvents
* using ObjectContext.GRAPH_CHANGE_SUBJECT.
*/
public CayenneContext(DataChannel channel, boolean changeEventsEnabled,
boolean syncEventsEnabled) {
this.graphAction = new CayenneContextGraphAction(this);
this.graphManager = new CayenneContextGraphManager(
this,
changeEventsEnabled,
syncEventsEnabled);
setChannel(channel);
}
public DataChannel getChannel() {
return channel;
}
/**
* Sets the context channel, setting up a listener for channel events.
*/
public void setChannel(DataChannel channel) {
if (this.channel != channel) {
if (this.mergeHandler != null) {
this.mergeHandler.active = false;
this.mergeHandler = null;
}
this.channel = channel;
EventManager eventManager = (channel != null)
? channel.getEventManager()
: null;
if (eventManager != null) {
this.mergeHandler = new CayenneContextMergeHandler(this);
// listen to our channel events...
// note that we must reset listener on channel switch, as there is no
// guarantee that a new channel uses the same EventManager.
EventUtil.listenForChannelEvents(channel, mergeHandler);
}
}
}
/**
* Returns true if this context posts individual object modification events. Subject
* used for these events is ObjectContext.GRAPH_CHANGED_SUBJECT.
*/
public boolean isChangeEventsEnabled() {
return graphManager.changeEventsEnabled;
}
/**
* Returns true if this context posts lifecycle events. Subjects used for these events
* are
* ObjectContext.GRAPH_COMMIT_STARTED_SUBJECT, ObjectContext.GRAPH_COMMITTED_SUBJECT,
* ObjectContext.GRAPH_COMMIT_ABORTED_SUBJECT, ObjectContext.GRAPH_ROLLEDBACK_SUBJECT..
*/
public boolean isLifecycleEventsEnabled() {
return graphManager.lifecycleEventsEnabled;
}
/**
* Returns an EntityResolver that provides mapping information needed for
* CayenneContext operation. If EntityResolver is not set, this method would obtain
* and cache one from the underlying DataChannel.
*/
public EntityResolver getEntityResolver() {
// load entity resolver on demand
if (entityResolver == null) {
synchronized (this) {
if (entityResolver == null) {
setEntityResolver(channel.getEntityResolver());
}
}
}
return entityResolver;
}
public void setEntityResolver(EntityResolver entityResolver) {
this.entityResolver = entityResolver;
}
public GraphManager getGraphManager() {
return graphManager;
}
CayenneContextGraphManager internalGraphManager() {
return graphManager;
}
CayenneContextGraphAction internalGraphAction() {
return graphAction;
}
/**
* Commits changes to uncommitted objects. First checks if there are changes in this
* context and if any changes are detected, sends a commit message to remote Cayenne
* service via an internal instance of CayenneConnector.
*/
public void commitChanges() {
doCommitChanges();
}
GraphDiff doCommitChanges() {
GraphDiff commitDiff = null;
synchronized (graphManager) {
if (graphManager.hasChanges()) {
graphManager.graphCommitStarted();
try {
commitDiff = channel.onSync(this, graphManager
.getDiffsSinceLastFlush(), DataChannel.FLUSH_CASCADE_SYNC);
}
catch (Throwable th) {
graphManager.graphCommitAborted();
if (th instanceof CayenneRuntimeException) {
throw (CayenneRuntimeException) th;
}
else {
throw new CayenneRuntimeException("Commit error", th);
}
}
graphManager.graphCommitted(commitDiff);
}
}
return commitDiff;
}
public void rollbackChanges() {
synchronized (graphManager) {
if (graphManager.hasChanges()) {
GraphDiff diff = graphManager.getDiffs();
graphManager.graphReverted();
channel.onSync(this, diff, DataChannel.ROLLBACK_CASCADE_SYNC);
}
}
}
public void commitChangesToParent() {
synchronized (graphManager) {
if (graphManager.hasChangesSinceLastFlush()) {
GraphDiff diff = graphManager.getDiffsSinceLastFlush();
graphManager.graphFlushed();
channel.onSync(this, diff, DataChannel.FLUSH_NOCASCADE_SYNC);
}
}
}
public void rollbackChangesLocally() {
synchronized (graphManager) {
if (graphManager.hasChanges()) {
graphManager.graphReverted();
}
}
}
/**
* Deletes an object locally, scheduling it for future deletion from the external data
* store.
*/
public void deleteObject(Persistent object) {
new ObjectContextDeleteAction(this).performDelete(object);
}
/**
* Creates and registers a new Persistent object instance.
*/
public Persistent newObject(Class persistentClass) {
if (persistentClass == null) {
throw new NullPointerException("Persistent class can't be null.");
}
ObjEntity entity = getEntityResolver().lookupObjEntity(persistentClass);
if (entity == null) {
throw new CayenneRuntimeException("No entity mapped for class: "
+ persistentClass);
}
synchronized (graphManager) {
return createNewObject(new ObjectId(entity.getName()));
}
}
/**
* Runs a query, returning result as list.
*/
public List performQuery(Query query) {
List result = onQuery(this, query).firstList();
return result != null ? result : new ArrayList(1);
}
public QueryResponse performGenericQuery(Query query) {
return onQuery(this, query);
}
// TODO: Andrus, 2/2/2006 - make public once CayenneContext is officially declared to
// support DataChannel API.
QueryResponse onQuery(ObjectContext context, Query query) {
return new CayenneContextQueryAction(this, context, query).execute();
}
/**
* Converts a list of Persistent objects registered in some other ObjectContext to a
* list of objects local to this ObjectContext.
*
* Current limitation: all objects in the source list must be either in COMMITTED
* or in HOLLOW state.
*
*/
public Persistent localObject(ObjectId id, Persistent prototype) {
// TODO: Andrus, 1/26/2006 - this implementation is copied verbatim from
// DataContext. Somehow need to pull out the common code or implement inheritance
// ****** Copied from DataContext - start *******
if (id == null) {
throw new IllegalArgumentException("Null ObjectId");
}
ClassDescriptor descriptor = getEntityResolver().getClassDescriptor(
id.getEntityName());
Persistent cachedObject = (Persistent) getGraphManager().getNode(id);
// merge into an existing object
if (cachedObject != null) {
// TODO: Andrus, 1/24/2006 implement smart merge for modified objects...
if (cachedObject != prototype
&& cachedObject.getPersistenceState() != PersistenceState.MODIFIED
&& cachedObject.getPersistenceState() != PersistenceState.DELETED) {
descriptor.injectValueHolders(cachedObject);
if (prototype != null
&& prototype.getPersistenceState() != PersistenceState.HOLLOW) {
descriptor.shallowMerge(prototype, cachedObject);
if (cachedObject.getPersistenceState() == PersistenceState.HOLLOW) {
cachedObject.setPersistenceState(PersistenceState.COMMITTED);
}
}
}
return cachedObject;
}
// create and merge into a new object
else {
// Andrus, 1/26/2006 - note that there is a tricky case of a temporary object
// passed from peer DataContext... In the past we used to throw an exception
// or return null. Now that we can have a valid (but generally
// indistinguishible) case of such object passed from parent, we let it
// slip... Not sure what's the best way of handling it that does not involve
// breaking encapsulation of the DataChannel to detect where in the hierarchy
// this context is.
Persistent localObject;
synchronized (getGraphManager()) {
localObject = (Persistent) descriptor.createObject();
localObject.setObjectContext(this);
localObject.setObjectId(id);
getGraphManager().registerNode(id, localObject);
}
if (prototype != null) {
localObject.setPersistenceState(PersistenceState.COMMITTED);
descriptor.injectValueHolders(localObject);
descriptor.shallowMerge(prototype, localObject);
}
else {
localObject.setPersistenceState(PersistenceState.HOLLOW);
}
return localObject;
}
// ****** Copied from DataContext - end *******
}
/**
* Resolves an object if it is HOLLOW.
*/
public void prepareForAccess(Persistent object, String property) {
if (object.getPersistenceState() == PersistenceState.HOLLOW) {
ObjectId gid = object.getObjectId();
List objects = performQuery(new ObjectIdQuery(gid));
if (objects.size() == 0) {
throw new FaultFailureException(
"Error resolving fault, no matching row exists in the database for GlobalID: "
+ gid);
}
else if (objects.size() > 1) {
throw new FaultFailureException(
"Error resolving fault, more than one row exists in the database for GlobalID: "
+ gid);
}
}
}
public void propertyChanged(
Persistent object,
String property,
Object oldValue,
Object newValue) {
graphAction.handlePropertyChange(object, property, oldValue, newValue);
}
public Collection uncommittedObjects() {
synchronized (graphManager) {
return graphManager.dirtyNodes();
}
}
public Collection deletedObjects() {
synchronized (graphManager) {
return graphManager.dirtyNodes(PersistenceState.DELETED);
}
}
public Collection modifiedObjects() {
synchronized (graphManager) {
return graphManager.dirtyNodes(PersistenceState.MODIFIED);
}
}
public Collection newObjects() {
synchronized (graphManager) {
return graphManager.dirtyNodes(PersistenceState.NEW);
}
}
// ****** non-public methods ******
Persistent createNewObject(ObjectId id) {
ClassDescriptor descriptor = getEntityResolver().getClassDescriptor(
id.getEntityName());
Persistent object = (Persistent) descriptor.createObject();
// must follow this exact order of property initialization per CAY-653, i.e. have
// the id and the context in place BEFORE setPersistence is called
object.setObjectId(id);
object.setObjectContext(this);
object.setPersistenceState(PersistenceState.NEW);
descriptor.injectValueHolders(object);
graphManager.registerNode(object.getObjectId(), object);
graphManager.nodeCreated(object.getObjectId());
return object;
}
Persistent createFault(ObjectId id) {
ClassDescriptor descriptor = getEntityResolver().getClassDescriptor(
id.getEntityName());
Persistent object;
synchronized(graphManager) {
object = (Persistent) descriptor.createObject();
object.setPersistenceState(PersistenceState.HOLLOW);
object.setObjectContext(this);
object.setObjectId(id);
// note that this must be called AFTER setting persistence state, otherwise we'd
// get ValueHolders incorrectly marked as resolved
descriptor.injectValueHolders(object);
graphManager.registerNode(id, object);
}
return object;
}
}
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