    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 */
    017package org.apache.commons.jexl3.internal.introspection;
    018
    019import java.util.List;
    020import java.lang.reflect.Array;
    021
    022/**
    023 * Specialized executor to get a property from a List or array.
    024 * @since 2.0
    025 */
    026public final class ListGetExecutor extends AbstractExecutor.Get {
    027    /** The java.lang.reflect.Array.get method used as an active marker in ListGet. */
    028    private static final java.lang.reflect.Method ARRAY_GET =
    029            initMarker(Array.class, "get", Object.class, Integer.TYPE);
    030    /** The java.util.obj.get method used as an active marker in ListGet. */
    031    private static final java.lang.reflect.Method LIST_GET =
    032            initMarker(List.class, "get", Integer.TYPE);
    033    /** The property. */
    034    private final Integer property;
    035
    036    /**
    037     * Attempts to discover a ListGetExecutor.
    038     *
    039     * @param is the introspector
    040     * @param clazz the class to find the get method from
    041     * @param index the index to use as an argument to the get method
    042     * @return the executor if found, null otherwise
    043     */
    044    public static ListGetExecutor discover(final Introspector is, final Class<?> clazz, final Integer index) {
    045        if (index != null) {
    046            if (clazz.isArray()) {
    047                return new ListGetExecutor(clazz, ARRAY_GET, index);
    048            }
    049            if (List.class.isAssignableFrom(clazz)) {
    050                return new ListGetExecutor(clazz, LIST_GET, index);
    051            }
    052        }
    053        return null;
    054    }
    055
    056    /**
    057     * Creates an instance.
    058     * @param clazz he class the get method applies to
    059     * @param method the method held by this executor
    060     * @param index the index to use as an argument to the get method
    061     */
    062    private ListGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final Integer index) {
    063        super(clazz, method);
    064        property = index;
    065    }
    066
    067    @Override
    068    public Object getTargetProperty() {
    069        return property;
    070    }
    071
    072    @Override
    073    public Object invoke(final Object obj) {
    074        if (method == ARRAY_GET) {
    075            return Array.get(obj, property);
    076        }
    077        return ((List<?>) obj).get(property);
    078    }
    079
    080    @Override
    081    public Object tryInvoke(final Object obj, final Object identifier) {
    082        final Integer index = castInteger(identifier);
    083        if (obj != null && method != null
    084            && objectClass.equals(obj.getClass())
    085            && index != null) {
    086            if (method == ARRAY_GET) {
    087                return Array.get(obj, index);
    088            }
    089            return ((List<?>) obj).get(index);
    090        }
    091        return TRY_FAILED;
    092    }
    093}