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 018package org.apache.commons.jexl3.introspection; 019 020import org.apache.commons.jexl3.JexlException; 021 022/** 023 * Interface for getting values that appear to be properties. 024 * Ex. 025 * <code> 026 * ${foo.bar} 027 * </code> 028 * 029 * @since 1.0 030 */ 031public interface JexlPropertyGet { 032 /** 033 * Method used to get the property value of an object. 034 * 035 * @param obj the object to get the property value from. 036 * @return the property value. 037 * @throws Exception on any error. 038 */ 039 Object invoke(Object obj) throws Exception; 040 041 /** 042 * Attempts to reuse this JexlPropertyGet, checking that it is compatible with 043 * the actual set of arguments. 044 * 045 * @param obj the object to invoke the property get upon 046 * @param key the property key to get 047 * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded 048 * or failed. 049 * @throws JexlException.TryFailed if the underlying method was invoked but threw an exception 050 * ({@link java.lang.reflect.InvocationTargetException}) 051 */ 052 Object tryInvoke(Object obj, Object key) throws JexlException.TryFailed; 053 054 /** 055 * Checks whether a tryInvoke failed or not. 056 * 057 * @param rval the value returned by tryInvoke 058 * @return true if tryInvoke failed, false otherwise 059 */ 060 boolean tryFailed(Object rval); 061 062 /** 063 * Specifies if this JexlPropertyGet is cacheable and able to be reused for 064 * this class of object it was returned for. 065 * 066 * @return true if can be reused for this class, false if not 067 */ 068 boolean isCacheable(); 069}