/*
* 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.openjpa.util;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Set;
import org.apache.commons.collections.set.MapBackedSet;
/**
* Base class that provides utilities to change trackers.
*
* @author Abe White
*/
public abstract class AbstractChangeTracker
implements ChangeTracker {
/**
* Collection of added items. May be null.
*/
protected Collection add = null;
/**
* Collection of removed items. May be null.
*/
protected Collection rem = null;
/**
* Collection of changed items. May be null.
*/
protected Collection change = null;
private boolean _autoOff = true;
private boolean _track = false;
private Boolean _identity = null;
private int _seq = -1;
/**
* Constructor; supply configuration.
*/
public AbstractChangeTracker() {
}
/**
* Whether to automatically stop tracking when the number of changes
* exceeds the container size. Defaults to true.
*/
public boolean getAutoOff() {
return _autoOff;
}
/**
* Whether to automatically stop tracking when the number of changes
* exceeds the container size. Defaults to true.
*/
public void setAutoOff(boolean autoOff) {
_autoOff = autoOff;
}
public boolean isTracking() {
return _track;
}
public void startTracking() {
_track = true;
if (_seq == -1)
_seq = initialSequence();
reset();
}
/**
* Return the initial sequence value for this proxy. Typically this is
* the container size. Assumes an unordered collection by default,
* returning 0.
*/
protected int initialSequence() {
return 0;
}
public void stopTracking() {
_track = false;
_seq = -1;
reset();
}
/**
* Reset the state of the tracker.
*/
protected void reset() {
if (add != null)
add.clear();
if (rem != null)
rem.clear();
if (change != null)
change.clear();
_identity = null;
}
public Collection getAdded() {
return (add == null) ? Collections.EMPTY_LIST : add;
}
public Collection getRemoved() {
return (rem == null) ? Collections.EMPTY_LIST : rem;
}
public Collection getChanged() {
return (change == null) ? Collections.EMPTY_LIST : change;
}
/**
* Notify the tracker that the given object was added.
*/
protected void added(Object val) {
if (!_track)
return;
setIdentity(val);
add(val);
}
/**
* Mark the given value as added.
*/
protected abstract void add(Object val);
/**
* Notify the tracker that the given object was removed.
*/
protected void removed(Object val) {
if (!_track)
return;
setIdentity(val);
remove(val);
}
/**
* Mark the given value as removed.
*/
protected abstract void remove(Object val);
/**
* Notify the tracker that the given object was changed.
*/
protected void changed(Object val) {
if (!_track)
return;
setIdentity(val);
change(val);
}
/**
* Mark the given value as changed.
*/
protected abstract void change(Object val);
public int getNextSequence() {
return _seq;
}
public void setNextSequence(int seq) {
_seq = seq;
}
/**
* Create a new set for storing adds/removes/changes. Takes into account
* whether we need to use an identity set or standard set.
*/
protected Set newSet() {
if (_identity == Boolean.TRUE)
return MapBackedSet.decorate(new IdentityHashMap());
return new HashSet();
}
/**
* Set whether to use identity-based datastructures, and switch our current
* datastructures appropriately if needed. We use identity structures for
* PC types in case the user has coded them such that two objects with
* different identities can compare equals().
*/
private void setIdentity(Object val) {
if (val == null || _identity != null)
return;
if (ImplHelper.isManagedType(null, val.getClass()))
_identity = Boolean.TRUE;
else
_identity = Boolean.FALSE;
add = switchStructure(add, _identity.booleanValue());
rem = switchStructure(rem, _identity.booleanValue());
change = switchStructure(change, _identity.booleanValue());
}
/**
* Switch from an identity structure to a standard one, or vice versa.
*/
private static Collection switchStructure(Collection cur,
boolean identity) {
if (cur == null)
return null;
if (identity && cur instanceof HashSet) {
if (cur.isEmpty())
return null;
Set replace = MapBackedSet.decorate(new IdentityHashMap());
replace.addAll(cur);
return replace;
}
if (!identity && !(cur instanceof HashSet) && cur instanceof Set) {
if (cur.isEmpty())
return null;
return new HashSet(cur);
}
return cur;
}
}