    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
    018    package org.apache.commons.jexl2.internal;
    019
    020    import java.util.Map;
    021
    022     /**
    023     * Specialized executor to get a property from a Map.
    024      * @since 2.0
    025     */
    026    public final class MapGetExecutor extends AbstractExecutor.Get {
    027        /** The java.util.map.get method used as an active marker in MapGet. */
    028        private static final java.lang.reflect.Method MAP_GET =
    029                initMarker(Map.class, "get", Object.class);
    030        /** The property. */
    031        private final Object property;
    032
    033        /**
    034         * Creates an instance checking for the Map interface.
    035         * @param is the introspector
    036         * @param clazz the class that might implement the map interface
    037         * @param key the key to use in map.get(key)
    038         */
    039        public MapGetExecutor(Introspector is, Class<?> clazz, Object key) {
    040            super(clazz, discover(clazz));
    041            property = key;
    042        }
    043
    044        /** {@inheritDoc} */
    045        @Override
    046        public Object getTargetProperty() {
    047            return property;
    048        }
    049
    050        /**
    051         * Get the property from the map.
    052         * @param obj the map.
    053         * @return map.get(property)
    054         */
    055        @Override
    056        public Object execute(final Object obj) {
    057            @SuppressWarnings("unchecked") // ctor only allows Map instances - see discover() method
    058            final Map<Object,?> map = (Map<Object, ?>) obj;
    059            return map.get(property);
    060        }
    061
    062        /** {@inheritDoc} */
    063        @Override
    064        public Object tryExecute(final Object obj, Object key) {
    065            if (obj != null &&  method != null
    066                && objectClass.equals(obj.getClass())
    067                && (key == null || property.getClass().equals(key.getClass()))) {
    068                @SuppressWarnings("unchecked") // ctor only allows Map instances - see discover() method
    069                final Map<Object,?> map = (Map<Object, ?>) obj;
    070                return map.get(key);
    071            }
    072            return TRY_FAILED;
    073        }
    074
    075        /**
    076         * Finds the method to perform 'get' on a map.
    077         * @param clazz the class to introspect
    078         * @return a marker method, map.get
    079         */
    080        static java.lang.reflect.Method discover(Class<?> clazz) {
    081            return (Map.class.isAssignableFrom(clazz))? MAP_GET : null;
    082        }
    083    }