    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
    015package org.apache.tapestry5.util;
    016
    017import java.util.Map;
    018
    019import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    020import org.apache.tapestry5.ioc.internal.util.InternalCommonsUtils;
    021import org.apache.tapestry5.ioc.services.Coercion;
    022import org.apache.tapestry5.ioc.util.AvailableValues;
    023import 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 in release 5.3, but kept in same package for compatibility.
    031 * Moved tapestry-ioc to commons in release 5.4, but kept in same package for compatibility.
    032 *
    033 * @param <T>
    034 *            the type of enumeration
    035 */
    036public final class StringToEnumCoercion<T extends Enum> implements Coercion<String, T>
    037{
    038    private final Class<T> enumClass;
    039
    040    private final Map<String, T> stringToEnum = CollectionFactory.newCaseInsensitiveMap();
    041
    042    public StringToEnumCoercion(Class<T> enumClass)
    043    {
    044        this(enumClass, enumClass.getEnumConstants());
    045    }
    046
    047    public StringToEnumCoercion(Class<T> enumClass, T... values)
    048    {
    049        this.enumClass = enumClass;
    050
    051        for (T value : values)
    052            stringToEnum.put(value.name(), value);
    053    }
    054
    055    @Override
    056    public T coerce(String input)
    057    {
    058        if (InternalCommonsUtils.isBlank(input))
    059            return null;
    060
    061        T result = stringToEnum.get(input);
    062
    063        if (result == null)
    064        {
    065            String message = String.format("Input '%s' does not identify a value from enumerated type %s.", input,
    066                    enumClass.getName());
    067
    068            throw new UnknownValueException(message, new AvailableValues(enumClass.getName() + " enum constants",
    069                    stringToEnum));
    070        }
    071
    072        return result;
    073    }
    074
    075    /**
    076     * Allows an alias value (alternate) string to reference a value.
    077     *
    078     * @since 5.2.2
    079     */
    080    public StringToEnumCoercion<T> addAlias(String alias, T value)
    081    {
    082        stringToEnum.put(alias, value);
    083
    084        return this;
    085    }
    086
    087    public static <T extends Enum> StringToEnumCoercion<T> create(Class<T> enumClass)
    088    {
    089        return new StringToEnumCoercion<T>(enumClass);
    090    }
    091
    092}