public interface InvocationEvaluator
{
    /**
     * Method to evaluate the InvokeExpression, as part of the overall evaluation
     * defined by the InMemoryExpressionEvaluator.
     * @param expr The expression for invocation
     * @param invokedValue Value on which we are invoking this method
     * @param eval The overall evaluator for in-memory
     * @return The result
     */
    Object evaluate(InvokeExpression expr, Object invokedValue, InMemoryExpressionEvaluator eval);
}

public class StringToUpperCaseMethodEvaluator implements InvocationEvaluator
{
    protected static final Localiser LOCALISER = Localiser.getInstance(
        "org.datanucleus.Localisation", ObjectManagerFactoryImpl.class.getClassLoader());

    public Object evaluate(InvokeExpression expr, Object invokedValue, InMemoryExpressionEvaluator eval)
    {
        String method = expr.getOperation(); // Will be "toUpperCase"

        if (invokedValue == null)
        {
            return null;
        }
        if (!(invokedValue instanceof String))
        {
            throw new NucleusException(LOCALISER.msg("021011", 
                method, invokedValue.getClass().getName()));
        }
        return ((String)invokedValue).toUpperCase();
    }
}

<?xml version="1.0"?>
<plugin id="mydomain" name="DataNucleus plug-ins" provider-name="My Company">
    <extension point="org.datanucleus.store_query_methods">
        <query-method name="toUpperCase" class="java.lang.String"
            evaluator="org.datanucleus.query.evaluator.memory.StringToUpperCaseMethodEvaluator"/>
    </extension>
</plugin>

Query q = pm.newQuery("SELECT FROM mydomain.Product WHERE name.toUpperCase() == 'KETTLE'");