public void declareImports (String imports); public void declareParameters (String parameters); public void declareVariables (String variables); public void setOrdering (String ordering);
The following are optional elements of JDO queries:
Imports. Imports are specified with the declareImports method, and are given as a single, semicolon-delimited string following the standard Java import syntax. They are used so that you don't have to type out full class names when declaring parameters and variables, as described below.
Parameter declarations. Parameters act as placeholders in the filter string. They allow you to write a single query, then execute it multiple times, supplying new values each time. Parameters are specified via the declareParameters method. The syntax of the method's String argument follows the syntax for declaring the parameter signature of a Java method.
Variable declarations. Variables are typically used to test whether some item in a collection matches certain criteria. They are specified with the declareVariables method, using the standard Java syntax for variable declarations.
Ordering. Sometimes you would like the results of a query to be returned in a specific order. For example, you might want a list of all cars for sale in ascending order by price. The setOrdering method enables you to add ordering criteria to your queries. The String argument to the method is a comma-separated list of ordering declarations, where each declaration consists of a field name followed by the keywords "ascending" or "descending". The results will be ordered primarily by the first (left-most) ordering declaration. Wherever two results compare equal with this expression, the next ordering expression will be used to order them, and so on.