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    package org.apache.commons.jexl2.internal;
018    
019    import java.lang.reflect.InvocationTargetException;
020    
021    /**
022     * Specialized executor to get a property from an object.
023     * <p>Duck as in duck-typing for an interface like:
024     * <code>
025     * interface Get {
026     *      Object get(Object key);
027     * }
028     * </code>
029     * </p>
030     * @since 2.0
031     */
032    public final class DuckGetExecutor extends AbstractExecutor.Get {
033        /** The property. */
034        private final Object property;
035    
036        /**
037         * Creates an instance by attempting discovery of the get method.
038         * @param is the introspector
039         * @param clazz the class to introspect
040         * @param identifier the property to get
041         */
042        public DuckGetExecutor(Introspector is, Class<?> clazz, Object identifier) {
043            super(clazz, discover(is, clazz, identifier));
044            property = identifier;
045        }
046    
047        /** {@inheritDoc} */
048        @Override
049        public Object getTargetProperty() {
050            return property;
051        }
052    
053        /**
054         * Get the property from the object.
055         * @param obj the object.
056         * @return object.get(property)
057         * @throws IllegalAccessException Method is inaccessible.
058         * @throws InvocationTargetException Method body throws an exception.
059         */
060        @Override
061        public Object execute(Object obj)
062                throws IllegalAccessException, InvocationTargetException {
063            Object[] args = {property};
064            return method == null ? null : method.invoke(obj, args);
065        }
066    
067        /** {@inheritDoc} */
068        @Override
069        public Object tryExecute(Object obj, Object key) {
070            if (obj != null && method !=  null
071                // ensure method name matches the property name
072                && property.equals(key)
073                && objectClass.equals(obj.getClass())) {
074                try {
075                    Object[] args = {property};
076                    return method.invoke(obj, args);
077                } catch (InvocationTargetException xinvoke) {
078                    return TRY_FAILED; // fail
079                } catch (IllegalAccessException xill) {
080                    return TRY_FAILED;// fail
081                }
082            }
083            return TRY_FAILED;
084        }
085    
086        /**
087         * Discovers a method for a {@link GetExecutor.DuckGet}.
088         *@param is the introspector
089         *@param clazz the class to find the get method from
090         *@param identifier the key to use as an argument to the get method
091         *@return the method if found, null otherwise
092         */
093        private static java.lang.reflect.Method discover(Introspector is,
094                final Class<?> clazz, Object identifier) {
095            return is.getMethod(clazz, "get", makeArgs(identifier));
096        }
097    }