001    // Copyright 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.plastic;
016    
017    /**
018     * Allows read/write access directly to a field (bypassing accessors). Does not use reflection, even
019     * if the field is private (the normal case for Plastic classes).
020     */
021    public interface FieldHandle
022    {
023        /**
024         * Gets the current value of the field. If the field is a primitive value, then the primitive
025         * will be wrapped.
026         * 
027         * @throws NullPointerException
028         *             if the instance is null
029         * @throws ClassCastException
030         *             if the instance is not the type that contains the field
031         */
032        Object get(Object instance);
033    
034        /**
035         * Updates the current value of the field. If the field is a primitive value, then the newValue
036         * will be unwrapped automatically.
037         * 
038         * @throws NullPointerException
039         *             if the instance is null
040         * @throws NullPointerException
041         *             if the newValue is null and the field is a primitive type
042         * @throws ClassCastException
043         *             if the instance is not the type that contains the field
044         * @throws ClassCastException
045         *             if the newValue is not assignable to the field type (or not the matching wrapper type
046         *             for a primitive field)
047         */
048        void set(Object instance, Object newValue);
049    }