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 }