JDO Entity modification is not persisted - google-app-engine

Question

I'm using Google App Engine and I created an persistent entity using Google documentation about JDO. The class is the following:
#PersistenceCapable
public class Message {
#PrimaryKey
#Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
#Persistent
public long id;
#Persistent
public Text message;
#Persistent
public boolean isNew;
#Persistent
public long categoryId;
#Persistent
public boolean plus;
#Persistent
public Date lastUpdate;
Message(long id, String message, boolean isNew, long categoryId, Date lastUpdate, boolean plus) {
this.id = id;
this.message = new Text(message);
this.isNew = isNew;
this.categoryId = categoryId;
this.lastUpdate = lastUpdate;
this.plus = plus;
}
}
And than, I create the a HttpServlet with the following doPost code:
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/plain");
PrintWriter writer = resp.getWriter();
Date tenDaysAgo = new Date(new Date().getTime()-TEN_DAYS_IN_MILISSECOND);
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
Query queryMessages = pm.newQuery(Message.class);
queryMessages.setFilter("isNew == True && lastUpdate <= lastUpdateParam");
queryMessages.declareParameters(Date.class.getName() + " lastUpdateParam");
List<Message> results = (List<Message>) queryMessages.execute(tenDaysAgo);
for(Message msg : results) {
msg.isNew = false;
pm.makePersistent(msg);
}
//pm.makePersistentAll(results);
writer.print(results.size() + " messages changed.");
}finally {
pm.close();
}
}
But, when I do a post request I receive the message "3048 messages changed." and I check the database and the data is unchanged. The persistence is not working to persist the changes I made in the object. Even though using makePersistentAll( list ) or makePersistent( object ) the result is the same: no change in the database.
What I'm missing?
Thank you!

Answer 1

You need to create a JDO transaction to keep track of changes and then commit them to issue the update SQL statements:
pm.currentTransaction().begin();
for(Message msg : results) {
msg.isNew = false;
}
pm.currentTransaction().commit();