    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
    015package org.apache.tapestry5.internal.plastic;
    016
    017import org.apache.tapestry5.plastic.FieldHandle;
    018
    019public 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    @Override
    041    public Object get(Object instance)
    042    {
    043        checkNullInstance(instance, "get");
    044
    045        return shim.get(instance, fieldIndex);
    046    }
    047
    048    private void checkNullInstance(Object instance, String action)
    049    {
    050        if (instance == null)
    051            throw new NullPointerException(String.format(
    052                    "Unable to %s value of field %s of class %s, as provided instance is null.", action, fieldName,
    053                    className));
    054    }
    055
    056    @Override
    057    public void set(Object instance, Object newValue)
    058    {
    059        checkNullInstance(instance, "set");
    060
    061        shim.set(instance, fieldIndex, newValue);
    062    }
    063}