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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) 2015-2016, 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.memory;

import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.geotools.data.DataSourceException;
import org.geotools.data.FeatureWriter;
import org.geotools.data.Query;
import org.geotools.feature.simple.SimpleFeatureBuilder;
import org.geotools.feature.simple.SimpleFeatureImpl;
import org.geotools.filter.identity.FeatureIdImpl;
import org.geotools.geometry.jts.ReferencedEnvelope;
import org.geotools.util.factory.Hints;
import org.opengis.feature.IllegalAttributeException;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.feature.type.Name;
import org.opengis.filter.identity.FeatureId;

/** Update contents of MemoryDataStore. */
public class MemoryFeatureWriter implements FeatureWriter {
    MemoryState state;
    SimpleFeatureType featureType;
    Name typeName;

    Iterator iterator;

    SimpleFeature live = null;
    SimpleFeature current = null; // current Feature returned to user

    public MemoryFeatureWriter(MemoryState state, Query query) throws IOException {
        this.state = state;
        this.typeName = state.getEntry().getName();
        this.featureType = state.getFeatureType();

        MemoryEntry entry = state.getEntry();
        iterator = entry.getMemory().values().iterator();
    }

    public SimpleFeatureType getFeatureType() {
        return state.getFeatureType();
    }

    public SimpleFeature next() throws IOException, NoSuchElementException {
        if (hasNext()) {
            // existing content
            live = iterator.next();

            try {
                current = SimpleFeatureBuilder.copy(live);
            } catch (IllegalAttributeException e) {
                throw new DataSourceException("Unable to edit " + live.getID() + " of " + typeName);
            }
        } else {
            // new content
            live = null;

            try {
                current = SimpleFeatureBuilder.template(featureType, null);
            } catch (IllegalAttributeException e) {
                throw new DataSourceException("Unable to add additional Features of " + typeName);
            }
        }

        return current;
    }

    public void remove() throws IOException {
        if (iterator == null) {
            throw new IOException("FeatureWriter has been closed");
        }

        if (current == null) {
            throw new IOException("No feature available to remove");
        }

        if (live != null) {
            // remove existing content
            iterator.remove();
            live = null;
            current = null;
        } else {
            // cancel add new content
            current = null;
        }
    }

    public void write() throws IOException {
        if (iterator == null) {
            throw new IOException("FeatureWriter has been closed");
        }

        if (current == null) {
            throw new IOException("No feature available to write");
        }
        // preserve FeatureIDs during insert feature
        if (Boolean.TRUE.equals(current.getUserData().get(Hints.USE_PROVIDED_FID))) {
            if (current.getUserData().containsKey(Hints.PROVIDED_FID)) {
                String fid = (String) current.getUserData().get(Hints.PROVIDED_FID);
                FeatureId id = new FeatureIdImpl(fid);
                current =
                        new SimpleFeatureImpl(
                                current.getAttributes(), current.getFeatureType(), id);
            }
        }

        if (live != null) {
            if (live.equals(current)) {
                // no modifications made to current
                //
                live = null;
                current = null;
            } else {
                // accept modifications
                //
                try {
                    live.setAttributes(current.getAttributes());
                } catch (Exception e) {
                    throw new DataSourceException(
                            "Unable to accept modifications to "
                                    + live.getID()
                                    + " on "
                                    + typeName);
                }

                ReferencedEnvelope bounds = new ReferencedEnvelope();
                bounds.expandToInclude(new ReferencedEnvelope(live.getBounds()));
                bounds.expandToInclude(new ReferencedEnvelope(current.getBounds()));
                live = null;
                current = null;
            }
        } else {
            // add new content
            MemoryEntry entry = state.getEntry();
            entry.addFeature(current);
            current = null;
        }
    }

    public boolean hasNext() throws IOException {
        if (iterator == null) {
            throw new IOException("FeatureWriter has been closed");
        }
        return (iterator != null) && iterator.hasNext();
    }

    public void close() {
        if (iterator != null) {
            iterator = null;
        }

        if (featureType != null) {
            featureType = null;
        }
        current = null;
        live = null;
    }
}