001    // Copyright 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.func;
016    
017    /**
018     * Interface for operation {@link Flow#map(Mapper)} to define how Flow elements are mapped from one type
019     * to another (or otherwise transformed).
020     * <p>
021     * This changed in 5.3 from an abstract base class to an interface.
022     * 
023     * @since 5.2.0
024     * @param <S>
025     *            type of source flow
026     * @param <T>
027     *            type of target (output) flow
028     */
029    public interface Mapper<S, T>
030    {
031        /**
032         * Implemented in subclasses to map an element from the source flow to an element of the target
033         * flow.
034         */
035        T map(S element);
036    }