    001    // Copyright 2007, 2008, 2010, 2011 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    // http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.util;
    016
    017    import java.util.Map;
    018
    019    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    020    import org.apache.tapestry5.ioc.internal.util.InternalUtils;
    021    import org.apache.tapestry5.ioc.services.Coercion;
    022    import org.apache.tapestry5.ioc.util.AvailableValues;
    023    import org.apache.tapestry5.ioc.util.UnknownValueException;
    024
    025    /**
    026     * A {@link org.apache.tapestry5.ioc.services.Coercion} for converting strings into an instance of a particular
    027     * enumerated type. The {@link Enum#name() name} is used as the key to identify the enum instance, in a case-insensitive
    028     * fashion.
    029     * <p>
    030     * Moved from tapestry-core to tapestry-ioc is release 5.3, but kept in same package for compatibility.
    031     *
    032     * @param <T>
    033     *            the type of enumeration
    034     */
    035    public final class StringToEnumCoercion<T extends Enum> implements Coercion<String, T>
    036    {
    037        private final Class<T> enumClass;
    038
    039        private final Map<String, T> stringToEnum = CollectionFactory.newCaseInsensitiveMap();
    040
    041        public StringToEnumCoercion(Class<T> enumClass)
    042        {
    043            this(enumClass, enumClass.getEnumConstants());
    044        }
    045
    046        public StringToEnumCoercion(Class<T> enumClass, T... values)
    047        {
    048            this.enumClass = enumClass;
    049
    050            for (T value : values)
    051                stringToEnum.put(value.name(), value);
    052        }
    053
    054        public T coerce(String input)
    055        {
    056            if (InternalUtils.isBlank(input))
    057                return null;
    058
    059            T result = stringToEnum.get(input);
    060
    061            if (result == null)
    062            {
    063                String message = String.format("Input '%s' does not identify a value from enumerated type %s.", input,
    064                        enumClass.getName());
    065
    066                throw new UnknownValueException(message, new AvailableValues(enumClass.getName() + " enum constants",
    067                        stringToEnum));
    068            }
    069
    070            return result;
    071        }
    072
    073        /**
    074         * Allows an alias value (alternate) string to reference a value.
    075         *
    076         * @since 5.2.2
    077         */
    078        public StringToEnumCoercion<T> addAlias(String alias, T value)
    079        {
    080            stringToEnum.put(alias, value);
    081
    082            return this;
    083        }
    084
    085        public static <T extends Enum> StringToEnumCoercion<T> create(Class<T> enumClass)
    086        {
    087            return new StringToEnumCoercion<T>(enumClass);
    088        }
    089
    090    }