/*
* Copyright 2011 Vaadin Ltd.
*
* Licensed 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 com.vaadin.data.util.sqlcontainer;
import java.io.Serializable;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;
import com.vaadin.data.util.sqlcontainer.query.FreeformQuery;
import com.vaadin.data.util.sqlcontainer.query.QueryDelegate;
import com.vaadin.data.util.sqlcontainer.query.TableQuery;
/**
* CacheFlushNotifier is a simple static notification mechanism to inform other
* SQLContainers that the contents of their caches may have become stale.
*/
class CacheFlushNotifier implements Serializable {
/*
* SQLContainer instance reference list and dead reference queue. Used for
* the cache flush notification feature.
*/
private static List<WeakReference<SQLContainer>> allInstances = new ArrayList<WeakReference<SQLContainer>>();
private static ReferenceQueue<SQLContainer> deadInstances = new ReferenceQueue<SQLContainer>();
/**
* Adds the given SQLContainer to the cache flush notification receiver list
*
* @param c
* Container to add
*/
public static void addInstance(SQLContainer c) {
removeDeadReferences();
if (c != null) {
allInstances.add(new WeakReference<SQLContainer>(c, deadInstances));
}
}
/**
* Removes dead references from instance list
*/
private static void removeDeadReferences() {
java.lang.ref.Reference<? extends SQLContainer> dead = deadInstances
.poll();
while (dead != null) {
allInstances.remove(dead);
dead = deadInstances.poll();
}
}
/**
* Iterates through the instances and notifies containers which are
* connected to the same table or are using the same query string.
*
* @param c
* SQLContainer that issued the cache flush notification
*/
public static void notifyOfCacheFlush(SQLContainer c) {
removeDeadReferences();
for (WeakReference<SQLContainer> wr : allInstances) {
if (wr.get() != null) {
SQLContainer wrc = wr.get();
if (wrc == null) {
continue;
}
/*
* If the reference points to the container sending the
* notification, do nothing.
*/
if (wrc.equals(c)) {
continue;
}
/* Compare QueryDelegate types and tableName/queryString */
QueryDelegate wrQd = wrc.getQueryDelegate();
QueryDelegate qd = c.getQueryDelegate();
if (wrQd instanceof TableQuery
&& qd instanceof TableQuery
&& ((TableQuery) wrQd).getTableName().equals(
((TableQuery) qd).getTableName())) {
wrc.refresh();
} else if (wrQd instanceof FreeformQuery
&& qd instanceof FreeformQuery
&& ((FreeformQuery) wrQd).getQueryString().equals(
((FreeformQuery) qd).getQueryString())) {
wrc.refresh();
}
}
}
}
}