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 *
33 * @since 2.0
34 */
35 public final class DuckGetExecutor extends AbstractExecutor.Get {
36
37 /**
38 * Attempts to discover a DuckGetExecutor.
39 *
40 * @param is the introspector
41 * @param clazz the class to find the get method from
42 * @param identifier the key to use as an argument to the get method
43 * @return the executor if found, null otherwise
44 */
45 public static DuckGetExecutor discover(final Introspector is, final Class<?> clazz, final Object identifier) {
46 final java.lang.reflect.Method method = is.getMethod(clazz, "get", identifier);
47 return method == null ? null : new DuckGetExecutor(clazz, method, identifier);
48 }
49
50 /** The property, may be null. */
51 private final Object property;
52
53 /**
54 * Creates an instance.
55 *
56 * @param clazz he class the get method applies to
57 * @param method the method held by this executor
58 * @param identifier the property to get
59 */
60 private DuckGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final Object identifier) {
61 super(clazz, method);
62 property = identifier;
63 }
64
65 @Override
66 public Object getTargetProperty() {
67 return property;
68 }
69
70 @Override
71 public Object invoke(final Object obj) throws IllegalAccessException, InvocationTargetException {
72 final Object[] args = {property};
73 return method == null ? null : method.invoke(obj, args);
74 }
75
76 @Override
77 public Object tryInvoke(final Object obj, final Object key) {
78 if (obj != null
79 && objectClass.equals(obj.getClass())
80 // ensure method name matches the property name
81 && method != null
82 && (property == null && key == null
83 || property != null && property.equals(key))) {
84 try {
85 final Object[] args = {property};
86 return method.invoke(obj, args);
87 } catch (IllegalAccessException | IllegalArgumentException xill) {
88 return TRY_FAILED; // fail
89 } catch (final InvocationTargetException xinvoke) {
90 throw JexlException.tryFailed(xinvoke); // throw
91 }
92 }
93 return TRY_FAILED;
94 }
95 }