User's Manual

Chapter 9. Persistence Tutorial 81
}
To retrieve all users whose last name is "Smith", do the following:
DataQuery query = session.retrieveQuery("UsersGroups");
query.addEqualsFilter("lastName", "Smith")
while (query.next()) {
System.out.println("First name = " + query.get("firstName") +
"; Last name = " + query.get("lastName") +
"; Group = " + query.get("groupName"));
}
To get all users whose last name starts with "S", use the addFilter method:
DataQuery query = session.retrieveQuery("UsersGroups");
// FilterFactory is explained below
query.addFilter\
(query.getFilterFactory().startsWith("lastName", "S", false));
while (query.next()) {
System.out.println("First name = " + query.get("firstName") +
"; Last name = " + query.get("lastName") +
"; Group = " + query.get("groupName"));
}
9.5.1.3. Complex Filters
For more complex queries, it is helpful to understand the role of each interface that deals with Fil-
ters.
• Filter — This class represents a single expression for part of a "where" clause. For instance, a
Filter could be "foo = :bar" with a value associated with "bar" (e.g. "foo = 3").
• CompoundFilter — This class extends Filter and provides the ability to add filters together
using the AND and OR keywords.
• FilterFactory — This class is responsible for handing out filters. It has methods such as "sim-
ple", "equals", "notEquals", "lessThan", "greaterThan", "startsWith", "contains", and "endsWith".
If a user is using Oracle or Postgres, all these methods check whether the value is null, and if so,
act correctly (e.g., use "foo is null" instead of "foo = null").
• DataQuery — This class allows you to add filters as well as get a reference to the FilterFactory. If
you need a FilterFactory but do not have a DataQuery, use Session.getFilterFactory().
If you want to filter the query based on certain conditions, you can incrementally build up your query
as follows:
DataQuery query = session.retrieveQuery("UsersGroups");
FilterFactory factory = query.getFilterFactory();
if (beginLetter != null) {
query.addFilter(factory.lessThan("firstLetter", beginLetter, true));
}
if (lastLetter != null) {
query.addFilter(factory.greaterThan("firstLetter", beginLetter, true));
}
while (query.next()) {