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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2002-2016, 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.
 */
package org.geotools.data.store;

import java.io.IOException;
import org.geotools.data.DataUtilities;
import org.geotools.data.FeatureReader;
import org.geotools.data.collection.DelegateFeatureReader;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.data.simple.SimpleFeatureIterator;
import org.geotools.feature.FeatureCollection;
import org.geotools.feature.collection.DecoratingSimpleFeatureCollection;
import org.geotools.feature.visitor.CountVisitor;
import org.geotools.feature.visitor.FeatureAttributeVisitor;
import org.geotools.filter.FilterAttributeExtractor;
import org.opengis.feature.FeatureVisitor;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.feature.type.AttributeDescriptor;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.PropertyName;

/**
 * SimpleFeatureCollection decorator which decorates a feature collection "re-typing" its schema
 * based on attributes specified in a query.
 *
 * @author Justin Deoliveira, The Open Planning Project
 */
public class ReTypingFeatureCollection extends DecoratingSimpleFeatureCollection {

    SimpleFeatureType featureType;

    public ReTypingFeatureCollection(
            FeatureCollection delegate,
            SimpleFeatureType featureType) {
        this(DataUtilities.simple(delegate), featureType);
    }

    public ReTypingFeatureCollection(
            SimpleFeatureCollection delegate, SimpleFeatureType featureType) {
        super(delegate);
        this.featureType = featureType;
    }

    public SimpleFeatureType getSchema() {
        return featureType;
    }

    public FeatureReader reader() throws IOException {
        return new DelegateFeatureReader(getSchema(), features());
    }

    public SimpleFeatureIterator features() {
        return new ReTypingFeatureIterator(delegate.features(), delegate.getSchema(), featureType);
    }

    @Override
    protected boolean canDelegate(FeatureVisitor visitor) {
        return isTypeCompatible(visitor, featureType);
    }

    /**
     * Checks if the visitor is accessing only properties available in the specified feature type,
     * or as a special case, if it's a count visitor accessing no properties at all
     */
    public static boolean isTypeCompatible(FeatureVisitor visitor, SimpleFeatureType featureType) {
        if (visitor instanceof FeatureAttributeVisitor) {
            // pass through if the target schema contains all the necessary attributes
            FilterAttributeExtractor extractor = new FilterAttributeExtractor(featureType);
            for (Expression e : ((FeatureAttributeVisitor) visitor).getExpressions()) {
                e.accept(extractor, null);
            }

            for (PropertyName pname : extractor.getPropertyNameSet()) {
                AttributeDescriptor att = (AttributeDescriptor) pname.evaluate(featureType);
                if (att == null) {
                    return false;
                }
            }
            return true;
        } else if (visitor instanceof CountVisitor) {
            return true;
        }
        return false;
    }
}