001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.operation.expression; 023 024import java.beans.ConstructorProperties; 025 026import cascading.flow.FlowProcess; 027import cascading.operation.Filter; 028import cascading.operation.FilterCall; 029import cascading.tuple.Tuple; 030import org.codehaus.janino.ExpressionEvaluator; 031 032/** 033 * Class ExpressionFilter dynamically resolves a given expression using argument {@link Tuple} values. Any Tuple that 034 * returns true for the given expression will be removed from the stream. This {@link Filter} 035 * is based on the <a href="http://www.janino.net/">Janino</a> compiler. 036 * <p> 037 * Specifically this filter uses the {@link ExpressionEvaluator}, thus the syntax from that class is inherited here. 038 * <p> 039 * An expression may use field names directly as parameters in the expression, or field positions with the syntax 040 * "$n", where n is an integer. 041 * <p> 042 * Given an argument tuple with the fields "a" and "b", the following expression returns true: <br> 043 * {@code a + b == $0 + $1}<br> 044 * <p> 045 * Further, the types of the tuple elements will be coerced into the given parameterTypes. Regardless of the actual 046 * tuple element values, they will be converted to the types expected by the expression. 047 * <p> 048 * Field names used in the expression should be valid Java variable names; for example, '+' or '-' are not allowed. 049 * Also the use of a field name that begins with an upper-case character is likely to fail and should be avoided. 050 */ 051public class ExpressionFilter extends ExpressionOperation implements Filter<ScriptOperation.Context> 052 { 053 /** 054 * Constructor ExpressionFilter creates a new ExpressionFilter instance. 055 * <p> 056 * This constructor, when used with incoming arguments that have type information, the argument field 057 * names can be used directly in the the expression, for example {@code a + b }. The type of {@code a} and {@code b} 058 * will be inherited from the incoming argument fields. 059 * <p> 060 * Or, if the incoming argument selector is {@link cascading.tuple.Fields#NONE}, an expression using only static method calls 061 * or constants can be used, for example {@code Math.random() < SomeClass.someValue() }. 062 * 063 * @param expression of type String 064 */ 065 @ConstructorProperties({"expression"}) 066 public ExpressionFilter( String expression ) 067 { 068 super( expression ); 069 } 070 071 /** 072 * Constructor ExpressionFilter creates a new ExpressionFilter instance. 073 * 074 * @param expression of type String 075 * @param parameterType of type Class 076 */ 077 @ConstructorProperties({"expression", "parameterType"}) 078 public ExpressionFilter( String expression, Class parameterType ) 079 { 080 super( expression, parameterType ); 081 } 082 083 /** 084 * Constructor ExpressionFilter creates a new ExpressionFilter instance. 085 * 086 * @param expression of type String 087 * @param parameterNames of type String[] 088 * @param parameterTypes of type Class[] 089 */ 090 @ConstructorProperties({"expression", "parameterNames", "parameterTypes"}) 091 public ExpressionFilter( String expression, String[] parameterNames, Class[] parameterTypes ) 092 { 093 super( expression, parameterNames, parameterTypes ); 094 } 095 096 @Override 097 public boolean isRemove( FlowProcess flowProcess, FilterCall<Context> filterCall ) 098 { 099 return (Boolean) evaluate( filterCall.getContext(), filterCall.getArguments() ); 100 } 101 }