001    // Copyright 2010 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.services;
016    
017    /**
018     * Used when accessing the private instance variables of a component instance.
019     * 
020     * @see TransformField#getAccess()
021     * @since 5.2.0
022     */
023    public interface FieldAccess
024    {
025        /**
026         * Reads the value of the field of the provided instance.
027         * 
028         * @param instance
029         *            object containing field to read
030         */
031        Object read(Object instance);
032    
033        /**
034         * Updates the value of the field within the instance.
035         * 
036         * @param instance
037         *            object containing field to update
038         * @param value
039         *            new value for field
040         */
041        void write(Object instance, Object value);
042    }