/* * GeoTools - The Open Source Java GIS Toolkit * http://geotools.org * * (C) 2005-2008, Open Source Geospatial Foundation (OSGeo) * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; * version 2.1 of the License. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * Created on May 11, 2005, 6:21 PM */ package org.geotools.filter.function; import static org.geotools.filter.capability.FunctionNameImpl.parameter; import java.io.IOException; import java.util.Collections; import java.util.List; import java.util.logging.Level; import java.util.logging.Logger; import org.geotools.data.simple.SimpleFeatureCollection; import org.geotools.feature.visitor.CalcResult; import org.geotools.feature.visitor.UniqueVisitor; import org.geotools.filter.Expression; import org.geotools.filter.FunctionExpressionImpl; import org.geotools.filter.IllegalFilterException; import org.geotools.filter.capability.FunctionNameImpl; import org.opengis.filter.capability.FunctionName; /** * Calculates the unique value of an attribute for a given FeatureCollection * and Expression. * * @author Cory Horner * @since 2.2M2 * * * @source $URL$ */ public class Collection_UniqueFunction extends FunctionExpressionImpl { /** The logger for the filter module. */ private static final Logger LOGGER = org.geotools.util.logging.Logging.getLogger( "org.geotools.filter.function"); SimpleFeatureCollection previousFeatureCollection = null; Object unique = null; public static FunctionName NAME = new FunctionNameImpl("Collection_Unique", parameter("unique", Object.class), parameter("expression", Object.class)); /** * Creates a new instance of Collection_UniqueFunction */ public Collection_UniqueFunction() { super(NAME); } public int getArgCount() { return 1; } /** * Calculate unique (using FeatureCalc) - only one parameter is used. * * @param collection collection to calculate the unique * @param expression Single Expression argument * * @return An object containing the unique value of the attributes * * @throws IllegalFilterException * @throws IOException */ static CalcResult calculateUnique(SimpleFeatureCollection collection, Expression expression) throws IllegalFilterException, IOException { UniqueVisitor uniqueVisitor = new UniqueVisitor(expression); collection.accepts(uniqueVisitor, null); return uniqueVisitor.getResult(); } /** * The provided arguments are evaulated with respect to the * FeatureCollection. * *
* For an aggregate function (like unique) please use the WFS mandated XPath * syntax to refer to featureMember content. *
* *
* To refer to all 'X': featureMember/asterisk/X
*