001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.tapestry.services; 016 017 /** 018 * Wrapper around the OGNL library. 019 * 020 * @author Howard M. Lewis Ship 021 * @since 4.0 022 */ 023 public interface ExpressionEvaluator 024 { 025 /** 026 * Reads a property of the target, defined by the expression. 027 * 028 * @throws org.apache.hivemind.ApplicationRuntimeException 029 * if the expression can not be parsed, or if some other error occurs during 030 * evaluation of the expression. 031 */ 032 public Object read(Object target, String expression); 033 034 /** 035 * Reads a property of the target, defined by the (previously compiled) expression. 036 * 037 * @throws org.apache.hivemind.ApplicationRuntimeException 038 * if some other error occurs during evaluation of the expression. 039 */ 040 public Object readCompiled(Object target, Object expression); 041 042 /** 043 * Updates a property of the target, defined by the expression. 044 * 045 * @throws org.apache.hivemind.ApplicationRuntimeException 046 * if the expression can not be parsed, or if some other error occurs during 047 * evaluation of the expression. 048 */ 049 public void write(Object target, String expression, Object value); 050 051 /** 052 * Updates a property of the target, defined by the (previously compiled) expression. 053 * 054 * @throws org.apache.hivemind.ApplicationRuntimeException 055 * if some other error occurs during evaluation of the expression. 056 */ 057 public void writeCompiled(Object target, Object expression, Object value); 058 059 /** 060 * Returns true if the expression evaluates to a constant or other literal value. 061 * 062 * @throws org.apache.hivemind.ApplicationRuntimeException 063 * if the expression is not valid 064 */ 065 public boolean isConstant(String expression); 066 }