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 * http://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
18 package org.apache.commons.jexl3.introspection;
19
20 import org.apache.commons.jexl3.JexlException;
21
22 /**
23 * Interface for getting values that appear to be properties.
24 * Ex.
25 * <code>
26 * ${foo.bar}
27 * </code>
28 *
29 * @since 1.0
30 */
31 public interface JexlPropertyGet {
32 /**
33 * Method used to get the property value of an object.
34 *
35 * @param obj the object to get the property value from.
36 * @return the property value.
37 * @throws Exception on any error.
38 */
39 Object invoke(Object obj) throws Exception;
40
41 /**
42 * Specifies if this JexlPropertyGet is cacheable and able to be reused for
43 * this class of object it was returned for.
44 *
45 * @return true if can be reused for this class, false if not
46 */
47 boolean isCacheable();
48
49 /**
50 * Checks whether a tryInvoke failed or not.
51 *
52 * @param rval the value returned by tryInvoke
53 * @return true if tryInvoke failed, false otherwise
54 */
55 boolean tryFailed(Object rval);
56
57 /**
58 * Attempts to reuse this JexlPropertyGet, checking that it is compatible with
59 * the actual set of arguments.
60 *
61 * @param obj the object to invoke the property get upon
62 * @param key the property key to get
63 * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
64 * or failed.
65 * @throws JexlException.TryFailed if the underlying method was invoked but threw an exception
66 * ({@link java.lang.reflect.InvocationTargetException})
67 */
68 Object tryInvoke(Object obj, Object key) throws JexlException.TryFailed;
69 }