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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       * Attempts to reuse this JexlPropertyGet, checking that it is compatible with
43       * the actual set of arguments.
44       *
45       * @param obj the object to invoke the property get upon
46       * @param key the property key to get
47       * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
48       * or failed.
49       * @throws JexlException.TryFailed if the underlying method was invoked but threw an exception
50       * ({@link java.lang.reflect.InvocationTargetException})
51       */
52      Object tryInvoke(Object obj, Object key) throws JexlException.TryFailed;
53  
54      /**
55       * Checks whether a tryInvoke failed or not.
56       *
57       * @param rval the value returned by tryInvoke
58       * @return true if tryInvoke failed, false otherwise
59       */
60      boolean tryFailed(Object rval);
61  
62      /**
63       * Specifies if this JexlPropertyGet is cacheable and able to be reused for
64       * this class of object it was returned for.
65       *
66       * @return true if can be reused for this class, false if not
67       */
68      boolean isCacheable();
69  }