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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.util;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.PersistenceState;
import org.apache.cayenne.Persistent;
import org.apache.cayenne.ValueHolder;
/**
* A list of persistent objects lazily resolved on the first access.
*
* @since 1.2
*/
public class PersistentObjectList extends RelationshipFault implements List, ValueHolder,
PersistentObjectCollection {
// wrapped objects list
protected List objectList;
// track additions/removals in unresolved...
protected LinkedList addedToUnresolved;
protected LinkedList<Object> removedFromUnresolved;
// exists for the benefit of custom serialization schemes such as the one in Hessian.
@SuppressWarnings("unused")
private PersistentObjectList() {
}
/**
* Creates PersistentObjectList initializing it with list owner persistent object and
* relationship name that this list maps to.
*
* @param relationshipOwner persistent object that owns this list.
* @param relationshipName a query used to resolve the list
*/
public PersistentObjectList(Persistent relationshipOwner, String relationshipName) {
super(relationshipOwner, relationshipName);
}
/**
* Returns whether this list is not yet resolved and requires a fetch.
*/
public boolean isFault() {
if (objectList != null) {
return false;
}
// resolve on the fly if owner is transient... Can't do it in constructor, as
// object may be in an inconsistent state during construction time
// synchronize??
else if (isTransientParent()) {
objectList = new LinkedList();
return false;
}
else {
return true;
}
}
/**
* Turns itself into a fault, thus forcing a refresh on the next access.
*/
public void invalidate() {
setObjectList(null);
}
public Object setValueDirectly(Object value) throws CayenneRuntimeException {
if (value == null || value instanceof List) {
Object old = this.objectList;
setObjectList((List) value);
return old;
}
else {
throw new CayenneRuntimeException("Value must be a list, got: "
+ value.getClass().getName());
}
}
public Object getValue() throws CayenneRuntimeException {
return resolvedObjectList();
}
public Object getValueDirectly() throws CayenneRuntimeException {
return objectList;
}
public Object setValue(Object value) throws CayenneRuntimeException {
resolvedObjectList();
return setValueDirectly(objectList);
}
public void setObjectList(List objectList) {
this.objectList = objectList;
}
// ====================================================
// Standard List Methods.
// ====================================================
public boolean add(Object o) {
if ((isFault()) ? addLocal(o) : objectList.add(o)) {
postprocessAdd(o);
return true;
}
return false;
}
public void add(int index, Object o) {
resolvedObjectList().add(index, o);
postprocessAdd(o);
}
public boolean addAll(Collection c) {
if (resolvedObjectList().addAll(c)) {
// TODO: here we assume that all objects were added, while addAll may
// technically return true and add only some objects... need a smarter
// approach (maybe use "contains" in postprocessAdd"?)
postprocessAdd(c);
return true;
}
return false;
}
public boolean addAll(int index, Collection c) {
if (resolvedObjectList().addAll(index, c)) {
// TODO: here we assume that all objects were added, while addAll may
// technically return true and add only some objects... need a smarter
// approach (maybe use "contains" in postprocessAdd"?)
postprocessAdd(c);
return true;
}
return false;
}
public void clear() {
List resolved = resolvedObjectList();
postprocessRemove(resolved);
resolved.clear();
}
public boolean contains(Object o) {
return resolvedObjectList().contains(o);
}
public boolean containsAll(Collection c) {
return resolvedObjectList().containsAll(c);
}
@Override
public boolean equals(Object o) {
if (o == null) {
return false;
}
if (!(o instanceof PersistentObjectList)) {
return false;
}
return resolvedObjectList().equals(
((PersistentObjectList) o).resolvedObjectList());
}
@Override
public int hashCode() {
return 37 + resolvedObjectList().hashCode();
}
public Object get(int index) {
return resolvedObjectList().get(index);
}
public int indexOf(Object o) {
return resolvedObjectList().indexOf(o);
}
public boolean isEmpty() {
return resolvedObjectList().isEmpty();
}
public Iterator iterator() {
return resolvedObjectList().iterator();
}
public int lastIndexOf(Object o) {
return resolvedObjectList().lastIndexOf(o);
}
public ListIterator listIterator() {
return resolvedObjectList().listIterator();
}
public ListIterator listIterator(int index) {
return resolvedObjectList().listIterator(index);
}
public Object remove(int index) {
Object removed = resolvedObjectList().remove(index);
postprocessRemove(removed);
return removed;
}
public boolean remove(Object o) {
if ((isFault()) ? removeLocal(o) : objectList.remove(o)) {
postprocessRemove(o);
return true;
}
return false;
}
public boolean removeAll(Collection c) {
if (resolvedObjectList().removeAll(c)) {
// TODO: here we assume that all objects were removed, while removeAll may
// technically return true and remove only some objects... need a smarter
// approach
postprocessRemove(c);
return true;
}
return false;
}
public boolean retainAll(Collection c) {
// TODO: handle object graoh change notifications on object removals...
return resolvedObjectList().retainAll(c);
}
public Object set(int index, Object o) {
Object oldValue = resolvedObjectList().set(index, o);
postprocessAdd(o);
postprocessRemove(oldValue);
return oldValue;
}
public int size() {
return resolvedObjectList().size();
}
public List subList(int fromIndex, int toIndex) {
// TODO: should we wrap a sublist into a list that does notifications on
// additions/removals?
return resolvedObjectList().subList(fromIndex, toIndex);
}
public Object[] toArray() {
return resolvedObjectList().toArray();
}
public Object[] toArray(Object[] a) {
return resolvedObjectList().toArray(a);
}
// ====================================================
// Tracking list modifications, and resolving it
// on demand
// ====================================================
/**
* Returns internal objects list resolving it if needed.
*/
protected List resolvedObjectList() {
if (isFault()) {
synchronized (this) {
// now that we obtained the lock, check
// if another thread just resolved the list
if (isFault()) {
List localList = resolveFromDB();
mergeLocalChanges(localList);
this.objectList = localList;
}
}
}
return objectList;
}
protected void clearLocalChanges() {
addedToUnresolved = null;
removedFromUnresolved = null;
}
protected void mergeLocalChanges(List fetchedList) {
// only merge if an object is in an uncommitted state
// any other state means that our local tracking
// is invalid...
if (isUncommittedParent()) {
if (removedFromUnresolved != null) {
fetchedList.removeAll(removedFromUnresolved);
}
// add only those that are not already on the list
// do not include transient objects...
if (addedToUnresolved != null && !addedToUnresolved.isEmpty()) {
Iterator it = addedToUnresolved.iterator();
while (it.hasNext()) {
Object next = it.next();
if (next instanceof Persistent) {
Persistent dataObject = (Persistent) next;
if (dataObject.getPersistenceState() == PersistenceState.TRANSIENT) {
continue;
}
}
if (!fetchedList.contains(next)) {
fetchedList.add(next);
}
}
}
}
// clear local information in any event
clearLocalChanges();
}
protected boolean addLocal(Object object) {
if (removedFromUnresolved != null) {
removedFromUnresolved.remove(object);
}
if (addedToUnresolved == null) {
addedToUnresolved = new LinkedList();
}
addedToUnresolved.addLast(object);
// this is really meaningless, since we don't know
// if an object was present in the list
return true;
}
protected boolean removeLocal(Object object) {
if (addedToUnresolved != null) {
addedToUnresolved.remove(object);
}
if (removedFromUnresolved == null) {
removedFromUnresolved = new LinkedList<Object>();
}
if (shouldAddToRemovedFromUnresolvedList(object)) {
removedFromUnresolved.addLast(object);
}
// this is really meaningless, since we don't know
// if an object was present in the list
return true;
}
/**
* @return whether object should be added to {@link #removedFromUnresolved} during
* removal
*/
protected boolean shouldAddToRemovedFromUnresolvedList(Object object) {
return true;
}
protected void postprocessAdd(Collection collection) {
Iterator it = collection.iterator();
while (it.hasNext()) {
postprocessAdd(it.next());
}
}
protected void postprocessRemove(Collection collection) {
Iterator it = collection.iterator();
while (it.hasNext()) {
postprocessRemove(it.next());
}
}
protected void postprocessAdd(Object addedObject) {
// notify ObjectContext
if (relationshipOwner.getObjectContext() != null) {
relationshipOwner.getObjectContext().propertyChanged(
relationshipOwner,
relationshipName,
null,
addedObject);
if (addedObject instanceof Persistent) {
Util.setReverse(
relationshipOwner,
relationshipName,
(Persistent) addedObject);
}
}
}
protected void postprocessRemove(Object removedObject) {
// notify ObjectContext
if (relationshipOwner.getObjectContext() != null) {
relationshipOwner.getObjectContext().propertyChanged(
relationshipOwner,
relationshipName,
removedObject,
null);
if (removedObject instanceof Persistent) {
Util.unsetReverse(
relationshipOwner,
relationshipName,
(Persistent) removedObject);
}
}
}
@Override
public String toString() {
return (objectList != null) ? objectList.toString() : "[<unresolved>]";
}
public void addDirectly(Object target) {
if (isFault()) {
addLocal(target);
}
else {
objectList.add(target);
}
}
public void removeDirectly(Object target) {
if (isFault()) {
removeLocal(target);
}
else {
objectList.remove(target);
}
}
}