1. I don't really know anything about java
2. I am not exactly a programmer, though I do know sql, (x)html and css.
3. I'm not trying to know too much about java

I need to do something to the example app, guestbook. It has somekind of sign in/out system. Author/sender is attached to every message.

I want the user to see only those messages that he himself sent (where the author is the same as the currently logged in user)

Java Code:
    private User author;
This is the query
Java Code:
    String query = "select from " + Greeting.class.getName();
    List<Greeting> greetings = (List<Greeting>) pm.newQuery(query).execute();
No matter what I do, it either shows all messages or none of them. If I can get this to work, then I can get "real" app work. When I get that done, I can say goodbye to java.

Using the Datastore with JDO - Google App Engine - Google Code