1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.jexl3.internal.introspection;
18
19 import java.lang.reflect.InvocationTargetException;
20
21 import org.apache.commons.jexl3.JexlException;
22
23 /**
24 * Specialized executor to get a property from an object.
25 * <p>Duck as in duck-typing for an interface like:
26 * <code>
27 * interface Get {
28 * Object get(Object key);
29 * }
30 * </code>
31 * </p>
32 * @since 2.0
33 */
34 public final class DuckGetExecutor extends AbstractExecutor.Get {
35 /**
36 * Attempts to discover a DuckGetExecutor.
37 * @param is the introspector
38 * @param clazz the class to find the get method from
39 * @param identifier the key to use as an argument to the get method
40 * @return the executor if found, null otherwise
41 */
42 public static DuckGetExecutor discover(final Introspector is, final Class<?> clazz, final Object identifier) {
43 final java.lang.reflect.Method method = is.getMethod(clazz, "get", identifier);
44 return method == null ? null : new DuckGetExecutor(clazz, method, identifier);
45 }
46
47 /** The property, may be null. */
48 private final Object property;
49
50 /**
51 * Creates an instance.
52 * @param clazz he class the get method applies to
53 * @param method the method held by this executor
54 * @param identifier the property to get
55 */
56 private DuckGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final Object identifier) {
57 super(clazz, method);
58 property = identifier;
59 }
60
61 @Override
62 public Object getTargetProperty() {
63 return property;
64 }
65
66 @Override
67 public Object invoke(final Object obj) throws IllegalAccessException, InvocationTargetException {
68 final Object[] args = {property};
69 return method == null ? null : method.invoke(obj, args);
70 }
71
72 @Override
73 public Object tryInvoke(final Object obj, final Object key) {
74 if (obj != null
75 && objectClass.equals(obj.getClass())
76 // ensure method name matches the property name
77 && method != null
78 && (property == null && key == null
79 || property != null && property.equals(key))) {
80 try {
81 final Object[] args = {property};
82 return method.invoke(obj, args);
83 } catch (IllegalAccessException | IllegalArgumentException xill) {
84 return TRY_FAILED; // fail
85 } catch (final InvocationTargetException xinvoke) {
86 throw JexlException.tryFailed(xinvoke); // throw
87 }
88 }
89 return TRY_FAILED;
90 }
91 }