org.apache.tapestry5.util.StringToEnumCoercion Maven / Gradle / Ivy

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Central module for Tapestry, containing interfaces to the Java Servlet API and all core services and components.

There is a newer version: 5.8.6

// Copyright 2007, 2008, 2010 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry5.util;

import java.util.Map;

import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
import org.apache.tapestry5.ioc.internal.util.InternalUtils;
import org.apache.tapestry5.ioc.services.Coercion;
import org.apache.tapestry5.ioc.util.AvailableValues;
import org.apache.tapestry5.ioc.util.UnknownValueException;

/**
 * A {@link org.apache.tapestry5.ioc.services.Coercion} for converting strings into an instance of a particular
 * enumerated type. The {@link Enum#name() name} is used as the key to identify the enum instance, in a case-insensitive
 * fashion.
 * 
 * @param 
 *            the type of enumeration
 */
public final class StringToEnumCoercion implements Coercion
{
    private final Class enumClass;

    private final Map stringToEnum = CollectionFactory.newCaseInsensitiveMap();

    public StringToEnumCoercion(Class enumClass)
    {
        this(enumClass, enumClass.getEnumConstants());
    }

    public StringToEnumCoercion(Class enumClass, T... values)
    {
        this.enumClass = enumClass;

        for (T value : values)
            stringToEnum.put(value.name(), value);
    }

    public T coerce(String input)
    {
        if (InternalUtils.isBlank(input))
            return null;

        T result = stringToEnum.get(input);

        if (result == null)
            throw new UnknownValueException(
                    PublicUtilMessages.missingEnumValue(input, enumClass, stringToEnum.keySet()), new AvailableValues(
                            enumClass.getName() + " enum constants", stringToEnum));

        return result;
    }

    /**
     * Allows an alias value (alternate) string to reference a value.
     * 
     * @since 5.2.2
     */
    public StringToEnumCoercion addAlias(String alias, T value)
    {
        stringToEnum.put(alias, value);

        return this;
    }

    public static  StringToEnumCoercion create(Class enumClass)
    {
        return new StringToEnumCoercion(enumClass);
    }

}