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.jexl2.internal;
018
019import 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 */
032public 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}