    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.internal.plastic;
    016
    017    import org.apache.tapestry5.plastic.FieldHandle;
    018
    019    public class FieldHandleImpl implements FieldHandle
    020    {
    021        private final String className, fieldName;
    022
    023        private final int fieldIndex;
    024
    025        protected volatile PlasticClassHandleShim shim;
    026
    027        public FieldHandleImpl(String className, String fieldName, int fieldIndex)
    028        {
    029            this.className = className;
    030            this.fieldName = fieldName;
    031            this.fieldIndex = fieldIndex;
    032        }
    033
    034        @Override
    035        public String toString()
    036        {
    037            return String.format("FieldHandle[%s#%s]", className, fieldName);
    038        }
    039
    040        public Object get(Object instance)
    041        {
    042            checkNullInstance(instance, "get");
    043
    044            return shim.get(instance, fieldIndex);
    045        }
    046
    047        private void checkNullInstance(Object instance, String action)
    048        {
    049            if (instance == null)
    050                throw new NullPointerException(String.format(
    051                        "Unable to %s value of field %s of class %s, as provided instance is null.", action, fieldName,
    052                        className));
    053        }
    054
    055        public void set(Object instance, Object newValue)
    056        {
    057            checkNullInstance(instance, "set");
    058
    059            shim.set(instance, fieldIndex, newValue);
    060        }
    061    }