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.lang.reflect.InvocationTargetException;
020import org.apache.commons.jexl3.JexlException;
021
022/**
023 * Specialized executor to get a property from an object.
024 * <p>Duck as in duck-typing for an interface like:
025 * <code>
026 * interface Get {
027 *      Object get(Object key);
028 * }
029 * </code>
030 * </p>
031 * @since 2.0
032 */
033public final class DuckGetExecutor extends AbstractExecutor.Get {
034    /** The property, may be null. */
035    private final Object property;
036
037    /**
038     * Attempts to discover a DuckGetExecutor.
039     * @param is the introspector
040     * @param clazz the class to find the get method from
041     * @param identifier the key to use as an argument to the get method
042     * @return the executor if found, null otherwise
043     */
044    public static DuckGetExecutor discover(final Introspector is, final Class<?> clazz, final Object identifier) {
045        final java.lang.reflect.Method method = is.getMethod(clazz, "get", makeArgs(identifier));
046        return method == null? null : new DuckGetExecutor(clazz, method, identifier);
047    }
048
049    /**
050     * Creates an instance.
051     * @param clazz he class the get method applies to
052     * @param method the method held by this executor
053     * @param identifier the property to get
054     */
055    private DuckGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final Object identifier) {
056        super(clazz, method);
057        property = identifier;
058    }
059
060    @Override
061    public Object getTargetProperty() {
062        return property;
063    }
064
065    @Override
066    public Object invoke(final Object obj) throws IllegalAccessException, InvocationTargetException {
067        final Object[] args = {property};
068        return method == null ? null : method.invoke(obj, args);
069    }
070
071    @Override
072    public Object tryInvoke(final Object obj, final Object key) {
073        if (obj != null
074                && objectClass.equals(obj.getClass())
075                // ensure method name matches the property name
076                && method != null
077                && ((property == null && key == null)
078                || (property != null && property.equals(key)))) {
079            try {
080                final Object[] args = {property};
081                return method.invoke(obj, args);
082            } catch (IllegalAccessException | IllegalArgumentException xill) {
083                return TRY_FAILED;// fail
084            } catch (final InvocationTargetException xinvoke) {
085                throw JexlException.tryFailed(xinvoke); // throw
086            }
087        }
088        return TRY_FAILED;
089    }
090}