001    /*
002     * Copyright (C) 2012 eXo Platform SAS.
003     *
004     * This is free software; you can redistribute it and/or modify it
005     * under the terms of the GNU Lesser General Public License as
006     * published by the Free Software Foundation; either version 2.1 of
007     * the License, or (at your option) any later version.
008     *
009     * This software is distributed in the hope that it will be useful,
010     * but WITHOUT ANY WARRANTY; without even the implied warranty of
011     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012     * Lesser General Public License for more details.
013     *
014     * You should have received a copy of the GNU Lesser General Public
015     * License along with this software; if not, write to the Free
016     * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017     * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018     */
019    
020    package org.crsh.cli.type;
021    
022    import java.util.Collections;
023    import java.util.Iterator;
024    import java.util.LinkedHashSet;
025    import java.util.ServiceConfigurationError;
026    import java.util.ServiceLoader;
027    import java.util.logging.Level;
028    import java.util.logging.Logger;
029    
030    /**
031     * A factory for value types.
032     */
033    public class ValueTypeFactory {
034    
035      /** A value type factory instance that provides a predefined set of value types. */
036      public static final ValueTypeFactory DEFAULT = new ValueTypeFactory();
037    
038      /** The known types. */
039      private final ValueType<?>[] types;
040    
041      private ValueTypeFactory() {
042        this.types = new ValueType<?>[]{ ValueType.STRING, ValueType.INTEGER, ValueType.BOOLEAN,
043            ValueType.ENUM, ValueType.PROPERTIES, ValueType.OBJECT_NAME, ValueType.THREAD, ValueType.FILE};
044      }
045    
046      /**
047       * Create a value type factory for the the default value types and the value types that the specified
048       * classloader will load.
049       *
050       * @param loader the loader
051       * @throws NullPointerException if the loader is null
052       */
053      public ValueTypeFactory(ClassLoader loader) throws NullPointerException {
054        if (loader == null) {
055          throw new NullPointerException("No null loader accepted");
056        }
057    
058        //
059        LinkedHashSet<ValueType> types = new LinkedHashSet<ValueType>();
060        Collections.addAll(types, DEFAULT.types);
061        Iterator<ValueType> sl = ServiceLoader.load(ValueType.class, loader).iterator();
062        while (sl.hasNext()) {
063          try {
064            ValueType type = sl.next();
065            types.add(type);
066          }
067          catch (ServiceConfigurationError e) {
068            // Log it
069            Logger logger = Logger.getLogger(ValueTypeFactory.class.getName());
070            logger.log(Level.WARNING, "Could not load value type factory", e);
071          }
072        }
073    
074        //
075        this.types = types.toArray(new ValueType[types.size()]);
076      }
077    
078      public <T, S extends T> ValueType<T> get(Class<S> clazz) {
079        ValueType<?> bestType = null;
080        int bestDegree = Integer.MAX_VALUE;
081        for (ValueType<?> type : types) {
082          int degree = type.getDistance(clazz);
083          if (degree != -1 && degree < bestDegree) {
084            bestType = type;
085            bestDegree = degree;
086          }
087        }
088        return (ValueType<T>)bestType;
089      }
090    }