CollectionConverter at revision 27557

package org.geotools.util;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

import org.geotools.factory.Hints;

/**
 * Converts among arrays and different collection classes.
 * <p>
 * THe following conversions are supported:
 * <ul>
 *   <li>Collection to Collection where collections are different types ( ex list to set )
 *   <li>Collection to Array
 *   <li>Array to Collection
 *   <li>Array to Array where the declared type of the target array is assignable from
 *   the declared type of the source array
 * </ul>
 * </p>
 *
 * @author Justin Deoliveira, The Open Planning Project
 *
 */
public class CollectionConverterFactory implements ConverterFactory {

    /**
     * Converter for collection to collection
     */
    protected static final Converter CollectionToCollection = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            //if source is already an instance nevermind
            if ( target.isInstance( source ) ) {
                return source;
            }

            //dynamically create and add
            Collection converted = newCollection( target );
            if ( converted != null ) {
                converted.addAll( (Collection) source );
            }

            return converted;
        }

    };

    /**
     * Converter for collection to array.
     */
    protected static final Converter CollectionToArray = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            Collection s = (Collection) source;
            Object array = Array.newInstance(target.getComponentType(), s.size());

            try {
                int x = 0;
                for ( Iterator i = s.iterator(); i.hasNext(); x++ ) {
                    Array.set( array, x, i.next() );
                }

                return array;
            }
            catch( Exception e ) {
                //Means an incompatable type assignment

            }

            return null;
        }

    };

    /**
     * Converter for array to collection.
     */
    protected static final Converter ArrayToCollection = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            Collection collection = newCollection(target);
            if ( collection != null ) {
                int length = Array.getLength(source);
                for ( int i = 0; i < length; i++ ) {
                    collection.add( Array.get( source, i) );
                }
            }

            return collection;
        }

    };

    /**
     * Converter for array to array.
     */
    protected static final Converter ArrayToArray = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
          //get the individual component types
            Class s = source.getClass().getComponentType();
            Class t = target.getComponentType();

            //make sure the source can be assiigned to the target
            if ( t.isAssignableFrom(s) ) {
                int length = Array.getLength(source);
                Object converted = Array.newInstance( t, length );

                for ( int i = 0; i < length; i++ ) {
                    Array.set(converted, i, Array.get( source, i ) );
                }

                return converted;
            }

            return null;
        }
    };

    protected static Collection newCollection( Class target ) throws Exception {
        if ( target.isInterface() ) {
            //try the common ones
            if ( List.class.isAssignableFrom( target ) ) {
                return new ArrayList();
            }
            if ( SortedSet.class.isAssignableFrom( target ) ) {
                return new TreeSet();
            }
            else if ( Set.class.isAssignableFrom( target ) ) {
                return new HashSet();
            }

            //could not figure out
            return null;
        }
        else {
            //instantiate directly
            return (Collection) target.newInstance();
        }
    }
    public Converter createConverter(Class source, Class target, Hints hints) {
        if ( ( Collection.class.isAssignableFrom( source ) || source.isArray() )
            && ( Collection.class.isAssignableFrom( target ) || target.isArray() ) ) {

            //both collections?
            if ( Collection.class.isAssignableFrom( source ) &&
                    Collection.class.isAssignableFrom( target ) ) {
               return CollectionToCollection;
            }

            //both arrays?
            if ( source.getClass().isArray() && target.isArray() ) {
                return ArrayToArray;
            }

            //collection to array?
            if ( Collection.class.isAssignableFrom( source ) && target.isArray() ) {
               return CollectionToArray;
            }

            //array to collection?
            if ( source.getClass().isArray() && Collection.class.isAssignableFrom( target ) ) {
                return ArrayToCollection;
            }
        }

        return null;
    }
}

/*
 *    Geotoolkit.org - An Open Source Java GIS Toolkit
 *    http://www.geotoolkit.org
 *
 *    (C) 2009-2012, Open Source Geospatial Foundation (OSGeo)
 *    (C) 2009-2012, Geomatys
 *
 *    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.geotoolkit.util.converter;

import java.util.Collection;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.io.Serializable;
import java.io.ObjectStreamException;
import net.jcip.annotations.Immutable;


/**
 * Handles conversions from {@link java.util.Collection} to various objects.
 *
 * @author Martin Desruisseaux (Geomatys)
 * @version 3.02
 *
 * @since 3.02
 * @module
 */
@Immutable
abstract class CollectionConverter<T> extends SimpleConverter<Collection<?>,T> implements Serializable {
    /**
     * For cross-version compatibility.
     */
    private static final long serialVersionUID = -4515250904953131514L;

    /**
     * Returns the source class, which is always {@link String}.
     */
    @Override
    @SuppressWarnings({"unchecked","rawtypes"})
    public final Class<Collection<?>> getSourceClass() {
        return (Class) Collection.class;
    }


    /**
     * Converter from {@link java.util.Collection} to {@link java.util.List}.
     *
     * @author Martin Desruisseaux (Geomatys)
     * @version 3.02
     *
     * @since 3.02
     */
    @Immutable
    static final class List extends CollectionConverter<java.util.List<?>> {
        private static final long serialVersionUID = 5492247760609833586L;
        public static final List INSTANCE = new List();
        private List() {
        }

        @Override
        @SuppressWarnings({"unchecked","rawtypes"})
        public Class<java.util.List<?>> getTargetClass() {
            return (Class) java.util.List.class;
        }

        @Override
        public java.util.List<?> convert(final Collection<?> source) {
            if (source == null) {
                return null;
            }
            if (source instanceof java.util.List<?>) {
                return (java.util.List<?>) source;
            }
            return new ArrayList<>(source);
        }

        /** Returns the singleton instance on deserialization. */
        protected Object readResolve() throws ObjectStreamException {
            return INSTANCE;
        }
    }


    /**
     * Converter from {@link java.util.Collection} to {@link java.util.Set}.
     *
     * @author Martin Desruisseaux (Geomatys)
     * @version 3.02
     *
     * @since 3.02
     */
    @Immutable
    static final class Set extends CollectionConverter<java.util.Set<?>> {
        private static final long serialVersionUID = -4200659837453206164L;
        public static final Set INSTANCE = new Set();
        private Set() {
        }

        @Override
        @SuppressWarnings({"unchecked","rawtypes"})
        public Class<java.util.Set<?>> getTargetClass() {
            return (Class) java.util.Set.class;
        }

        @Override
        public java.util.Set<?> convert(final Collection<?> source) {
            if (source == null) {
                return null;
            }
            if (source instanceof java.util.Set<?>) {
                return (java.util.Set<?>) source;
            }
            return new LinkedHashSet<>(source);
        }

        /** Returns the singleton instance on deserialization. */
        protected Object readResolve() throws ObjectStreamException {
            return INSTANCE;
        }
    }
}