001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.jexl3.internal.introspection;
019
020import java.lang.reflect.Field;
021import org.apache.commons.jexl3.introspection.JexlPropertyGet;
022
023/**
024 * A JexlPropertyGet for public fields.
025 */
026public final class FieldGetExecutor implements JexlPropertyGet {
027    /**
028     * The public field.
029     */
030    private final Field field;
031
032    /**
033     * Attempts to discover a FieldGetExecutor.
034     *
035     * @param is the introspector
036     * @param clazz the class to find the get method from
037     * @param identifier the key to use as an argument to the get method
038     * @return the executor if found, null otherwise
039     */
040    public static JexlPropertyGet discover(final Introspector is, final Class<?> clazz, final String identifier) {
041        if (identifier != null) {
042            final Field field = is.getField(clazz, identifier);
043            if (field != null) {
044                return new FieldGetExecutor(field);
045            }
046        }
047        return null;
048    }
049    /**
050     * Creates a new instance of FieldPropertyGet.
051     * @param theField the class public field
052     */
053    private FieldGetExecutor(final Field theField) {
054        field = theField;
055    }
056
057    @Override
058    public Object invoke(final Object obj) throws Exception {
059        return field.get(obj);
060    }
061
062    @Override
063    public Object tryInvoke(final Object obj, final Object key) {
064        if (obj.getClass().equals(field.getDeclaringClass()) && key.equals(field.getName())) {
065            try {
066                return field.get(obj);
067            } catch (final IllegalAccessException xill) {
068                return Uberspect.TRY_FAILED;
069            }
070        }
071        return Uberspect.TRY_FAILED;
072    }
073
074    @Override
075    public boolean tryFailed(final Object rval) {
076        return rval == Uberspect.TRY_FAILED;
077    }
078
079    @Override
080    public boolean isCacheable() {
081        return true;
082    }
083
084}