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 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
028 * @version $Id: JexlPropertyGet.java 889760 2009-12-11 18:42:49Z sebb $
029 */
030 public interface JexlPropertyGet {
031 /**
032 * Method used to get the property value of an object.
033 *
034 * @param obj the object to get the property value from.
035 * @return the property value.
036 * @throws Exception on any error.
037 */
038 Object invoke(Object obj) throws Exception;
039
040 /**
041 * Attempts to reuse this JexlPropertyGet, checking that it is compatible with
042 * the actual set of arguments.
043 * @param obj the object to invoke the property get upon
044 * @param key the property key to get
045 * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
046 * or failed.
047 */
048 Object tryInvoke(Object obj, Object key);
049
050 /**
051 * Checks whether a tryInvoke failed or not.
052 * @param rval the value returned by tryInvoke
053 * @return true if tryInvoke failed, false otherwise
054 */
055 boolean tryFailed(Object rval);
056
057 /**
058 * Specifies if this JexlPropertyGet is cacheable and able to be reused for
059 * this class of object it was returned for.
060 *
061 * @return true if can be reused for this class, false if not
062 */
063 boolean isCacheable();
064 }