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 */ 017package org.apache.activemq.filter.function; 018 019import org.apache.activemq.filter.FunctionCallExpression; 020import org.apache.activemq.filter.MessageEvaluationContext; 021 022/** 023 * Interface required for objects that will be registered as functions for use in selectors. Handles parse- 024 * time and evaluation-time operations. 025 */ 026public interface FilterFunction { 027 /** 028 * Check whether the function, as it is used, is valid. Checking arguments here will return errors 029 * to clients at the time invalid selectors are initially specified, rather than waiting until the selector is 030 * applied to a message. 031 * 032 * @param FunctionCallExpression expr - the full expression of the function call, as used. 033 * @return true - if the function call is valid; false - otherwise. 034 */ 035 public boolean isValid(FunctionCallExpression expr); 036 037 /** 038 * Determine whether the function, as it will be called, returns a boolean value. Called during 039 * expression parsing after the full expression for the function call, including its arguments, has 040 * been parsed. This allows functions with variable return types to function as boolean expressions in 041 * selectors without sacrificing parse-time checking. 042 * 043 * @param FunctionCallExpression expr - the full expression of the function call, as used. 044 * @return true - if the function returns a boolean value for its use in the given expression; 045 * false - otherwise. 046 */ 047 public boolean returnsBoolean(FunctionCallExpression expr); 048 049 050 /** 051 * Evaluate the function call in the given context. The arguments must be evaluated, as-needed, by the 052 * function. Note that boolean expressions must return Boolean objects. 053 * 054 * @param FunctionCallExpression expr - the full expression of the function call, as used. 055 * @param MessageEvaluationContext message - the context within which to evaluate the call. 056 */ 057 public Object evaluate(FunctionCallExpression expr, MessageEvaluationContext message) 058 throws javax.jms.JMSException; 059} 060