/**
* Copyright 2010 Daniel Guermeur and Amy Unruh
*
* 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.
*
* See http://connectrapp.appspot.com/ for a demo, and links to more information
* about this app and the book that it accompanies.
*/
package com.metadot.book.connectr.server.migrations;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;
import java.util.List;
import java.util.Map;
import javax.jdo.PersistenceManager;
import javax.jdo.Query;
import javax.jdo.JDOHelper;
import com.google.appengine.api.datastore.Cursor;
import org.datanucleus.store.appengine.query.JDOCursorHelper;
import com.metadot.book.connectr.server.PMF;
import com.metadot.book.connectr.server.domain.FriendDetails;
import com.metadot.book.connectr.server.migrations.Migration;
/**
* A migration to initialize a new 'urls' field of Friend.
* This particular migration is not strictly necessary, as GAE will
* in fact handle the uninitialized field gracefully. However, it is
* included for purposes of example
*/
public class FriendMigration implements Migration {
public Map<String, String> migrate_up(String cursorString, int range, Map<String,String> params) {
Query q = null;
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
q = pm.newQuery(FriendDetails.class);
if (cursorString != null) {
Cursor cursor = Cursor.fromWebSafeString(cursorString);
Map<String, Object> extensionMap = new HashMap<String, Object>();
extensionMap.put(JDOCursorHelper.CURSOR_EXTENSION, cursor);
q.setExtensions(extensionMap);
}
q.setRange(0, range);
@SuppressWarnings("unchecked")
List<FriendDetails> results = (List<FriendDetails>) q.execute();
if (results.size() > 0) {
for (FriendDetails friendd : results) {
// initialize the new field if necessary
Set<String> urls = friendd.getUrls();
if (urls == null || urls.isEmpty()) {
if (urls == null) {
friendd.setUrls(new HashSet<String>());
}
JDOHelper.makeDirty(friendd, "urls");
}
}
Cursor cursor = JDOCursorHelper.getCursor(results);
cursorString = cursor.toWebSafeString();
}
else {
// no results
cursorString = null;
}
}
finally {
q.closeAll();
pm.close();
}
Map<String,String> res = new HashMap<String,String>();
res.put("cursor", cursorString);
return res;
}
// a no-op for this class
public Map<String, String> migrate_down(String cs, int range, Map<String,String> params) {
return null;
}
}