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 */
017
018 package org.apache.commons.jexl2.introspection;
019
020 /**
021 * Interface for getting values that appear to be properties.
022 * Ex.
023 * <code>
024 * ${foo.bar}
025 * </code>
026 * @since 1.0
027 */
028 public interface JexlPropertyGet {
029 /**
030 * Method used to get the property value of an object.
031 *
032 * @param obj the object to get the property value from.
033 * @return the property value.
034 * @throws Exception on any error.
035 */
036 Object invoke(Object obj) throws Exception;
037
038 /**
039 * Attempts to reuse this JexlPropertyGet, checking that it is compatible with
040 * the actual set of arguments.
041 * @param obj the object to invoke the property get upon
042 * @param key the property key to get
043 * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
044 * or failed.
045 */
046 Object tryInvoke(Object obj, Object key);
047
048 /**
049 * Checks whether a tryInvoke failed or not.
050 * @param rval the value returned by tryInvoke
051 * @return true if tryInvoke failed, false otherwise
052 */
053 boolean tryFailed(Object rval);
054
055 /**
056 * Specifies if this JexlPropertyGet is cacheable and able to be reused for
057 * this class of object it was returned for.
058 *
059 * @return true if can be reused for this class, false if not
060 */
061 boolean isCacheable();
062 }